Mathis on Graphene? Any hints?

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Mathis on Graphene? Any hints?

Post by Cr6 on Sun Aug 23, 2015 1:46 am

Just wanted to examine how "Graphene" is expressed in the Charge Field.  This apparently is a high focus area of research at the moment.

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Re: Mathis on Graphene? Any hints?

Post by Cr6 on Thu Aug 27, 2015 2:13 am

I think I found something on this:
-------
http://milesmathis.com/desig.pdf

110c - Designer Electrons are really Photons

by Miles Mathis
Today's news [March 17, 2012] included a report from the National Accelerator Laboratory SLAC that “designer electrons” were being created in manufactured structures that resembled graphene. The interesting sentence is this one:

Initially, the electrons in this structure had graphene-like properties; for example, unlike ordinary electrons, they had no mass and traveled as if they were moving at the speed of light in a vacuum. But researchers were then able to tune these electrons in ways that are difficult to do in real graphene.

According to current theory, there should be no such beast as a designer electron. This shouldn't be happening, and yet they are selling it to you as no big deal. Yes, it is sold as a big deal as a matter of high-tech, but it is not being sold as the theory-ender it is. The electron is one of the fundamental particles of QM and QED, and beyond the Relativity transforms it cannot vary. You cannot do a Relativity transform on an electron to give it no mass or a speed of c. If you take an electron to a velocity of c, it has infinite mass, not zero mass. So these people at SLAC should know this isn't initially an electron. Since it has the properties of a photon—speed c and zero mass—why are they calling it an electron here?

Because:

By writing complex patterns that mimicked changes in carbon-carbon bond lengths and strengths in graphene, the researchers were able to restore the electrons’ mass in small, selected areas.

You can't do that with photons, they think, so these must be electrons. But what is happening is that the created photons are being re-energized up to the electron level, using my spin stacking method. We are seeing in the experiment the actual making of an electron from a photon. We are seeing proof of my particle unification, which shows that the photon and electron are the same particle, one with more spins than the other.

Although this should be fairly obvious to anyone doing even a quick scan of the data, the researchers won't go there as a matter of theory. Why? One, because they don't have the theory to cover it. You can't turn a photon that is a point particle into an electron, and their photon is a point particle. Two, because to admit it would bring down QM and QED from the foundations. So they simply gloss over it. They imply that this isn't a problem by not even mentioning it. They toot the horns on the high-tech side, while hiding the theory side completely.

Even more amazing is this:

“One of the wildest things we did was to make the electrons think they are in a huge magnetic field when, in fact, no real field had been applied, ”Manoharan said. They calculated the positions where carbon atoms in graphene should be, to make its electrons believe they were being exposed to magnetic fields ranging from zero to 60 Tesla, more than 30 percent higher than the strongest continuous magnetic field ever achieved on Earth. The researchers then moved carbon monoxide molecules to steer the electrons into precisely those positions, and the electrons responded by behaving exactly as predicted — as if they had been exposed to a real field.

Notice that we get no commentary on that, just that it is “wild.” But again, it completely overthrows the current model. How can positions alone create fields of 60 Tesla?

No answer from SLAC, but I can tell you. It is because SLAC is ignoring the charge field, as usual. I just showed how they ignore charge in accelerators, and they are doing it again here. To see what I mean, we can return for a moment to a recent paper of mine on the heliospheric current sheet, where we see them ignoring the electrical current of space. I do the simple math, showing that the number, though low, indicates an underlying charge field strength the equivalent of at least 3 million lightning bolts. We have the same thing here, with a magnetic field of 60 Tesla being created “from nothing.” The researchers can't get it through their heads that the created magnetic field is real, even after they measure it. They say that it is “as if” they had been exposed to a real field. But quanta don't react “as if” they are in a field. They either are or they are not. This isn't psychology, this is physics. Check the spelling! Given that the field is being created, the question is, “HOW is it being created?” Current theory has no way to explain it, which is precisely why we have to be told it is a mirage. You don't have to explain mirages, right? So the electrons are just “fooled.”

But the field is real. The magnetic field of 60 Tesla is there. Where did it come from? It comes from the charge field. As I have been screaming for years, charge exists even in the absence of ions. Photons are there even when no ions are present to create the E/M fields we measure. So there are unmeasured photon potentials existing at all times. To see how these are created, you have to study my nuclear diagrams, which show how atoms recycle this charge field, creating the underlying potentials.

What this means in this current experiment is that the spacing of the carbon monoxide in the molecular structure is creating the potentials that then energize these photon/electrons. We are seeing part of the great power tied up in the charge field.

This is not zero-point energy, although like this energy, zero-point energy is coming from the charge field. There is no zero-point energy. Zero-point energy is a made-up term, used to fill a hole in current theory. Because current theory has forgotten about charge, it needs manufactured ideas like zero-point energy and dark energy to fill the gap.
Again, charge is made up of real photons with real radii and real mass. They are not virtual and they are not point particles. They create real potentials, just like wind does. And charge is much “heavier” than anyone understands. In fact, photonic matter outweighs baryonic matter by 19 to 1.

Although I am told daily that there is no evidence for my theories, there is evidence for it on a daily basis, more each week.



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Re: Mathis on Graphene? Any hints?

Post by Cr6 on Sat Sep 05, 2015 1:27 am

Here's a recent paper on "Klein tunnelling in graphene":

http://www.europhysicsnews.org/component/content/article?id=313
---
How massless electrons tunnel through graphene (Vol. 43 No. 2)

Klein tunnelling in one dimension. An electron incident from the left on a sharp potential step (the blue arrow indicates its direction of motion)

Electrons moving in graphene behave in an unusual way, as demonstrated by 2010 Nobel Prize laureates for physics A. Geim and K. Novoselov, who performed transport experiments on this one-carbon-atom-thick material. The present review explores the theoretical and experimental results to date of electrons tunnelling through energy barriers in graphene.

What could partly explain graphene's properties is that electrons travelling inside the material behave as if they were massless. Their behaviour is described by the so-called Dirac equation, which is normally used for high-energy particles such as neutrinos in vacuum moving at a velocity 300 times greater than that of electrons, nearing the speed of light.

In this review, the authors focus on the tunnelling effect occurring when Dirac electrons found in graphene are transmitted through different types of energy barriers. Contrary to the laws of classical mechanics, which govern larger scale particles that cannot cross energy barriers, electron tunnelling is possible in quantum mechanics - though only under restricted conditions, depending on the width and energy height of the barrier.

However, the Dirac electrons found in graphene can tunnel through energy barriers regardless of their width and energy height; a phenomenon called Klein tunnelling, described theoretically for 3D massive Dirac electrons by the Swedish physicist Oskar Klein in 1929. Graphene was the first material in which Klein tunnelling was observed experimentally, as massive Dirac electrons required energy barriers too large to be observed.

Klein tunnelling in graphene: optics with massless electrons
P.E. Allain and J.N. Fuchs, Eur. Phys. J. B 83, 301 (2011)


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Re: Mathis on Graphene? Any hints?

Post by Cr6 on Sat Sep 05, 2015 1:48 am

Quote from Mathis'  48. The Born-Einstein Letters paper:

http://milesmathis.com/born.html
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Other passages also act as propaganda, even when letters are not being suppressed. In letter 60, Born paraphrases Dirac:
the difficulties of QED [like infinite renormalization] "lie partly in the fact that Schrodinger's equations, and not those of Heisenberg, were used as a starting point." Here is a direct quote from Dirac: "For the purpose of setting up QED, Schrodinger's is a bad theory, Heisenberg's a good one."

As a sort of clarification of this assertion, Born comments on Schrodinger's mechanics in this way:
"The common objection is that one needs waves in spaces of many dimensions, and this canot be visualized."

But later Born admits that "Schrodinger himself had shown the mathematical equivalence of wave and matrix mechanics." So there are two glaring contradictions here. First, if wave and matrix mechanics are mathematically equivalent, there can hardly be a great deal of difference in choosing between the two for setting up QED. Of two maths that are really equivalent, one can hardly be good and the other bad. In fact, the simpler and more transparent math should always be preferred, given equivalence. This certainly applies to Schrodinger's equations, not Heisenberg's. Second, it is interesting here that a lack of visualization is a minus for Schrodinger but a plus for Heisenberg. The Copenhagen Interpretation—which everyone knows is connected to matrix mechanics—forbids its adherents from trying to visualize quantum motions and interactions. They treat its mathematical purity as its main selling point: the fact that it cannot be visualized is its main esoteric draw. It must be accepted simply because the math demands it. But then these same purists turn around and complain that Schrodinger does not offer us an easy visualization? The double standard could not be more transparent.

------------------

32. A Critique of General Relativity

http://milesmathis.com/gr.html


As an example of this, look at Paul Dirac's lead-in to the tensor calculus in his book General Theory of Relativity [1975]. He says,

One can easily imagine a curved two-dimensional space immersed in Euclidean three-dimensional space. In the same way, one can have a curved four-dimensional space immersed in a flat space of a larger number of dimensions. Such a curved space is called a Riemann space. A small region of it is approximately flat.1

That is his entire explanation of curved space. Afterwards he simply dives into the math. But his foundation is already cracked. First of all, a “curved two-dimensional space” is not two-dimensional. A curved two-dimensional space is three-dimensional, by definition. This mistake should already be a clue that Dirac is long on math and short on conceptual understanding and rigor. And it means that a curved four-dimensional space must be five-dimensional, in which case we need a variable and a variable assignment for this fifth dimension. We get neither from Dirac, and we have never gotten either from anyone else, including Einstein and Kaluza (Kaluza gave us the fifth variable but no assignment of it to any physical or temporal extension). Furthermore, Dirac's last sentence is necessary because he will use the calculus to do math in infinitesimal regions of Riemann space. But you can see that this is a sort of cheat: the mathematician postulates curvature and then ignores it by going to a tiny area where there is no curvature. I will have more to say about that later in this paper.

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Re: Mathis on Graphene? Any hints?

Post by Cr6 on Sat Sep 05, 2015 3:06 am

Graphene

http://www.graphenea.com/pages/graphene-properties

Graphene is, basically, a single atomic layer of graphite; an abundant mineral which is an allotrope of carbon that is made up of very tightly bonded carbon atoms organised into a hexagonal lattice. What makes graphene so special is its sp2 hybridisation and very thin atomic thickness (of 0.345Nm). These properties are what enable graphene to break so many records in terms of strength, electricity and heat conduction (as well as many others). Now, let’s explore just what makes graphene so special, what are its intrinsic properties that separate it from other forms of carbon, and other 2D crystalline compounds?

Fundamental Characteristics

Before monolayer graphene was isolated in 2004, it was theoretically believed that two dimensional compounds could not exist due to thermal instability when separated. However, once graphene was isolated, it was clear that it was actually possible, and it took scientists some time to find out exactly how. After suspended graphene sheets were studied by transmission electron microscopy, scientists believed that they found the reason to be due to slight rippling in the graphene, modifying the structure of the material. However, later research suggests that it is actually due to the fact that the carbon to carbon bonds in graphene are so small and strong that they prevent thermal fluctuations from destabilizing it.

Electronic Properties

One of the most useful properties of graphene is that it is a zero-overlap semimetal (with both holes and electrons as charge carriers) with very high electrical conductivity. Carbon atoms have a total of 6 electrons; 2 in the inner shell and 4 in the outer shell. The 4 outer shell electrons in an individual carbon atom are available for chemical bonding, but in graphene, each atom is connected to 3 other carbon atoms on the two dimensional plane, leaving 1 electron freely available in the third dimension for electronic conduction. These highly-mobile electrons are called pi (π) electrons and are located above and below the graphene sheet. These pi orbitals overlap and help to enhance the carbon to carbon bonds in graphene. Fundamentally, the electronic properties of graphene are dictated by the bonding and anti-bonding (the valance and conduction bands) of these pi orbitals.

Combined research over the last 50 years has proved that at the Dirac point in graphene, electrons and holes have zero effective mass. This occurs because the energy – movement relation (the spectrum for excitations) is linear for low energies near the 6 individual corners of the Brillouin zone. These electrons and holes are known as Dirac fermions, or Graphinos, and the 6 corners of the Brillouin zone are known as the Dirac points. Due to the zero density of states at the Dirac points, electronic conductivity is actually quite low. However, the Fermi level can be changed by doping (with electrons or holes) to create a material that is potentially better at conducting electricity than, for example, copper at room temperature.

Tests have shown that the electronic mobility of graphene is very high, with previously reported results above 15,000 cm2·V−1·s−1 and theoretically potential limits of 200,000 cm2·V−1·s−1 (limited by the scattering of graphene’s acoustic photons). It is said that graphene electrons act very much like photons in their mobility due to their lack of mass. These charge carriers are able to travel sub-micrometer distances without scattering; a phenomenon known as ballistic transport. However, the quality of the graphene and the substrate that is used will be the limiting factors. With silicon dioxide as the substrate, for example, mobility is potentially limited to 40,000 cm2·V−1·s−1.

Mechanical Strength

Another of graphene’s stand-out properties is its inherent strength. Due to the strength of its 0.142 Nm-long carbon bonds, graphene is the strongest material ever discovered, with an ultimate tensile strength of 130,000,000,000 Pascals (or 130 gigapascals), compared to 400,000,000 for A36 structural steel, or 375,700,000 for Aramid (Kevlar). Not only is graphene extraordinarily strong, it is also very light at 0.77milligrams per square metre (for comparison purposes, 1 square metre of paper is roughly 1000 times heavier). It is often said that a single sheet of graphene (being only 1 atom thick), sufficient in size enough to cover a whole football field, would weigh under 1 single gram.

What makes this particularly special is that graphene also contains elastic properties, being able to retain its initial size after strain. In 2007, Atomic force microscopic (AFM) tests were carried out on graphene sheets that were suspended over silicone dioxide cavities. These tests showed that graphene sheets (with thicknesses of between 2 and 8 Nm) had spring constants in the region of 1-5 N/m and a Young’s modulus (different to that of three-dimensional graphite) of 0.5 TPa. Again, these superlative figures are based on theoretical prospects using graphene that is unflawed containing no imperfections whatsoever and currently very expensive and difficult to artificially reproduce, though production techniques are steadily improving, ultimately reducing costs and complexity.

Optical Properties

Graphene’s ability to absorb a rather large 2.3% of white light is also a unique and interesting property, especially considering that it is only 1 atom thick. This is due to its aforementioned electronic properties; the electrons acting like massless charge carriers with very high mobility. A few years ago, it was proved that the amount of white light absorbed is based on the Fine Structure Constant, rather than being dictated by material specifics. Adding another layer of graphene increases the amount of white light absorbed by approximately the same value (2.3%). Graphene’s opacity of πα ≈ 2.3% equates to a universal dynamic conductivity value of G=e2/4ℏ (±2-3%) over the visible frequency range.

Due to these impressive characteristics, it has been observed that once optical intensity reaches a certain threshold (known as the saturation fluence) saturable absorption takes place (very high intensity light causes a reduction in absorption). This is an important characteristic with regards to the mode-locking of fibre lasers. Due to graphene’s properties of wavelength-insensitive ultrafast saturable absorption, full-band mode locking has been achieved using an erbium-doped dissipative soliton fibre laser capable of obtaining wavelength tuning as large as 30 nm.

In terms of how far along we are to understanding the true properties of graphene, this is just the tip of the iceberg. Before graphene is heavily integrated into the areas in which we believe it will excel at, we need to spend a lot more time understanding just what makes it such an amazing material. Unfortunately, while we have a lot of imagination in coming up with new ideas for potential applications and uses for graphene, it takes time to fully appreciate how and what graphene really is in order to develop these ideas into reality. This is not necessarily a bad thing, however, as it gives us opportunities to stumble over other previously under-researched or overlooked super-materials, such as the family of 2D crystalline structures that graphene has born.


------------

Graphene Supercapacitors

http://www.graphenea.com/pages/graphene-supercapacitors

Graphenea
Written By Jesus de La Fuente / CEO Graphenea / j.delafuente@graphenea.com

View Our Graphene Products / Read More Graphene Publications / Contact Us

Scientists have been struggling to develop energy storage solutions such as batteries and capacitors that can keep up with the current rate of electronic component evolution for a number of years. Unfortunately, the situation we are in now is that while we are able to store a large amount of energy in certain types of batteries, those batteries are very large, very heavy, and charge and release their energy relatively slowly. Capacitors, on the other hand, are able to be charged and release energy very quickly, but can hold much less energy than a battery. Graphene application developments though have lead to new possibilities for energy storage, with high charge and discharge rates, which can be made very cheaply. But before we go into specific details, it would be sensible to first outline the basics of energy storage and the potential goals of developing graphene as a supercapacitor.

Capacitors and supercapacitors explained

A capacitor is an energy storage medium similar to an electrochemical battery. Most batteries, while able to store a large amount of energy are relatively inefficient in comparison to other energy solutions such as fossil fuels. It is often said that a 1kg electrochemical battery is able to produce much less energy than 1 litre of gasoline; but this kind of comparison is extremely vague, mathematically illogical, and should be ignored. In fact, some electrochemical batteries can be relatively efficient, but that doesn’t get around the primary limiting factor in batteries replacing fossil fuels in commercial and industrial applications (for example, transportation); charge time.

High capacity batteries take a long time to charge. This is why electrically powered vehicles have not taken-off as well as we expected twenty or thirty years ago. While you are now able to travel 250 miles or more on one single charge in a car such as the Tesla Model S, it could take you over 43 hours to charge the vehicle using a standard 120v wall socket in order to drive back home. This is not acceptable for many car users. Capacitors, on the other hand, are able to be charged at a much higher rate, but store (as already mentioned) somewhat less energy.

Supercapacitors, also known as ultracapacitors, are able to hold hundreds of times the amount of electrical charge as standard capacitors, and are therefore suitable as a replacement for electrochemical batteries in many industrial and commercial applications. Supercapacitors also work in very low temperatures; a situation that can prevent many types of electrochemical batteries from working. For these reasons, supercapacitors are already being used in emergency radios and flashlights, where energy can be produced kinetically (by winding a handle, for example) and then stored in a supercapacitor for the device to use.

A conventional capacitor is made up of two layers of conductive materials (eventually becoming positively and negatively charged) separated by an insulator. What dictates the amount of charge a capacitor can hold is the surface area of the conductors, the distance between the two conductors and also the dielectric constant of the insulator. Supercapacitors are slightly different in the fact that they do not contain a solid insulator.

Instead the two conductive plates in a cell are coated with a porous material, most commonly activated carbon, and the cells are immersed in an electrolyte solution. The porous material ideally will have an extremely high surface area (1 gram of activated carbon can have an estimated surface area equal to that of a tennis court), and because the capacitance of a supercapacitor is dictated by the distance between the two layers and the surface area of the porous material, very high levels of charge can be achieved.

While supercapacitors are able to store much more energy than standard capacitors, they are limited in their ability to withstand high voltage. Electrolytic capacitors are able to run at hundreds of volts, but supercapacitors are generally limited to around 5 volts. However, it is possible to engineer a chain of supercapacitors to run at high voltages as long as the series is properly designed and controlled.

Graphene-based supercapacitors

Supercapacitors, unfortunately, are currently very expensive to produce, and at present the scalability of supercapacitors in industry is limiting the application options as energy efficiency is offset against cost efficiency. This is the reason why a paper by researchers at the UCLA has been so highly referred to within scientific circles and publications as they were able to produce supercapacitors made out of graphene by using a simple DVD LightScribe writer on a home PC. This idea of creating graphene monolayers by using thermo lithography is not necessarily a new one, as scientists from the US were able to produce graphene nanowires by using thermochemical nanolithography back in 2010; however, this new method avoids the use of an atomic force microscope in favour of a commercially available laser device that is already prevalent in many homes around the world.

Why are scientists looking at using graphene instead of the currently more popular activated carbon? Well, graphene is essentially a form of carbon, and while activated carbon has an extremely high relative surface area, graphene has substantially more. As we have already highlighted, one of the limitations to the capacitance of ultracapacitors is the surface area of the conductors. If one conductive material in a supercapacitor has a higher relative surface area than another, it will be better at storing electrostatic charge. Also, being a material made up of one single atomic layer, it is lighter. Another interesting point is that as graphene is essentially just graphite, which is a form of carbon, it is ecologically friendly, unlike most other forms of energy storage.

The efficiency of the supercapacitor is the important factor to bear in mind. In the past, scientists have been able to create supercapacitors that are able to store 150 Farads per gram, but some have suggested that the theoretical upper limit for graphene-based supercapacitors is 550 F/g. This is particularly impressive when compared against current technology: a commercially available capacitor able to store 1 Farad of electrostatic energy at 100 volts would be about 220mm high and weigh about 2kgs, though current supercapacitor technology is about the same, in terms of dimensions relative to energy storage values, as a graphene-based supercapacitor would be.

The future for graphene-based supercapacitors

Due to the lightweight dimensions of graphene based supercapacitors and the minimal cost of production coupled with graphene’s elastic properties and inherit mechanical strength, we will almost certainly see technology within the next five to ten years incorporating these supercapacitors. Also, with increased development in terms of energy storage limits for supercapacitors in general, graphene-based or hybrid supercapacitors will eventually be utilized in a number of different applications.

Vehicles that utilize supercapacitors are already prevalent in our society. One Chinese company is currently manufacturing buses that incorporate supercapacitor energy recovery systems, such as those used on Formula 1 cars, to store energy when braking and then converting that energy to power the vehicle until the next stop. Additionally, we will at some point in the next few years begin to see mobile telephones and other mobile electronic devices being powered by supercapacitors as not only can they be charged at a much higher rate than current lithium-ion batteries, but they also have the potential to last for a vastly greater length of time.

Other current and potential uses for supercapacitors are as power backup supplies for industry or even our own homes. Businesses can invest in power backup solutions that are able to store high levels of energy at high voltages, effectively offering full power available to them, to reduce the risk of having to limit production due to inadequate amounts of power. Alternatively, if you have a fuel cell vehicle that is able to store a large amount of electrical energy, then why not use it to help power your home in the event of a power outage?

We can expect that this scenario of using advanced energy storage and recovery solutions will become much more widely used in the coming years as the efficiency and energy density of supercapacitors increases, and the manufacturing costs decrease. While graphene-based supercapacitors are currently a viable solution in the future, technology needs to be developed to make this into a reality. But rest assured, many companies around the world are already trialling products using this technology and creating new ways to help subsidise the use of fossil-fuels and toxic chemicals in our ever-demanding strive for energy.

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Re: Mathis on Graphene? Any hints?

Post by Cr6 on Sat Sep 05, 2015 11:39 pm

Looked at this article again on Graphene conversions. Mathis says that near graphene, the Charge Field could spin-up a photon to an electron.  Looks like this experiment may be doing this? (...also posted in Scientific Discoveries but reposted here.)
------

April 14, 2015
Graphene pushes the speed limit of light-to-electricity conversion

http://phys.org/news/2015-04-graphene-limit-light-to-electricity-conversion.html
(more at link...)

ICFO researchers Klaas-Jan Tielrooij, Lukasz Piatkowski, Mathieu Massicotte and Achim Woessner led by ICFO Prof. Frank Koppens and ICREA Prof. at ICFO Niek van Hulst, in collaboration with scientists from the research group led by Pablo Jarillo-Herrero at MIT and the research group led by Jeanie Lau at UC Riverside, have now demonstrated that a graphene-based photodetector converts absorbed light into an electrical voltage at an extremely high speed. The study, entitled "Generation of photovoltage in graphene on a femtosecond timescale through efficient carrier heating", has recently been published in Nature Nanotechnology.

The new device that the researchers developed is capable of converting light into electricity in less than 50 femtoseconds (a twentieth of a millionth of a millionth of a second). To do this, the researchers used a combination of ultrafast pulse-shaped laser excitation and highly sensitive electrical readout. As Klaas-Jan Tielrooij comments, "the experiment uniquely combined the ultrafast pulse shaping expertise obtained from single molecule ultrafast photonics with the expertise in graphene electronics. Facilitated by graphene's nonlinear photo-thermoelectric response, these elements enabled the observation of femtosecond photodetection response times."

The ultrafast creation of a photovoltage in graphene is possible due to the extremely fast and efficient interaction between all conduction band carriers in graphene. This interaction leads to a rapid creation of an electron distribution with an elevated electron temperature. Thus, the energy absorbed from light is efficiently and rapidly converted into electron heat. Next, the electron heat is converted into a voltage at the interface of two graphene regions with different doping. This photo-thermoelectric effect turns out to occur almost instantaneously, thus enabling the ultrafast conversion of absorbed light into electrical signals. As Prof. van Hulst states, "it is amazing how graphene allows direct non-linear detecting of ultrafast femtosecond (fs) pulses".

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Re: Mathis on Graphene? Any hints?

Post by Cr6 on Sat Sep 05, 2015 11:55 pm

From Mathis' "The Great Methane Stink":
------------

This new theory allows me to make several other predictions, ones that can be checked with current machines—as far as I know. I believe it should be possible to measure the charge being emitted laterally by the Carbon inside CO2, and I think it will be found to be different from the lateral emission of Carbon alone. In other words, we need CO2 in a solid (but still non-magnetic) state, and then we need to probe the Carbon in that molecule, mapping its lateral charge profile by some means. I believe we will find that the Carbon has a different nuclear make-up than Carbon alone. I think we will find that a single atom of Carbon has two alphas in its core, while an atom of Carbon in most molecules has one.

This ties into recent questions I have been asked about Fullerenes and irradiated graphites. It has been found that Carbon, although normally non-magnetic, can be very magnetic in some situations. I would suggest that the varying nuclear make-up of different forms of Carbon explains this in the most direct and mechanical way. It would appear that Carbon in compound with itself can re-arrange in the same way we saw it re-arranging in CO2, especially in an irradiated field or in long chains. Once you have two prongs on each end of Carbon and only one alpha in the core, this will create a spun-up through charge, which is what causes magnetism.

From the Period Four  paper:
------------

In closing, I need to tie up one weak spot. I have said that those inner holes needed to be filled in most cases, to prevent the charge field from dashing through there and causing dissolution. But if protons are working like fans, pushing charge through, how does that prevent dissolution? If charge going through is dangerous, pushing charge through even faster won't help, will it?

Actually, it does, and this is because the danger from charge going through those holes was incoherent and/or unfocused charge. With no protons channeling charge, you of course have unchanneled charge. What is unchanneled charge? It is charge with no real direction. If those holes are open, charge can be arriving from any direction, with any spin. It will then move into that axis alpha on any vector, and most of those vectors won't be through vectors. In other words, the charge will go into the alpha, but it won't pass straight through. It will get into the alpha from the side and cause all kinds of trouble, since it isn't channeled charge. That alpha is channeling up or down, and so this unruly charge from the side is a menace. But once you put a proton in that hole, you have channeled charge. The charge is both spin coherent and linearized, so it passes straight through that axis alpha with minimal effect. I won't say no effect, since we saw above that protons in those holes can diminish conduction by a small amount. But with protons in the inner holes, the nucleus is in no danger of dissolution. The charge passes straight through in an orderly way.

I have now fielded a good question from a reader. He asks, “Don't you have charge being affected in opposite ways here? When channeled charge passes through the axis level, you say it interferes with conduction. But then you say it 'boosts' charge in Selenium. Isn't interference the opposite of boosting? How can that work?” It works because Selenium isn't conducting. You get conduction with elements like Arsenic and Copper, which have different numbers of protons top and bottom. Or you can get magnetic conduction with elements like Iron, but then you need more protons in the axis than in the carousel. Neither of those things is true of Selenium. Therefore, when the crossing charge meets the main axis charge in Selenium, it can only boost the charge. Some charge gets captured, you see, which acts like a boost. Remember, the interference I was talking about with conduction is actually a capturing of charge as well. But because it is captured by charge that is being conducted through the axis instead of charge being channeled into the carousel level, it ends up lowering the total instead of increasing it. Just think about it: we add an equal amount of charge to the top and bottom inner holes. So the north charge is increased by the same amount as the south charge. But the south charge was twice as strong as the north to start with (because the south has two protons pulling in charge while the north has one). Therefore, after adding equal amounts to both, the north charge is no longer half the south. It is a tiny bit more than half. Which means when they meet, we now get a tiny bit more cancellation. The north charge is a tiny bit stronger than it was, so it cancels a bit more than half of the south charge, giving us less conduction. But since Selenium isn't conducting, it doesn't feel experience this cancellation. It only experiences the boost. When elements have equal numbers of protons north, south and in the carousel level, the axis charge is pulled into the carousel level from the nuclear center, and so it never crosses.

To read more about energy transfer by metals, you may now consult my newest paper on the Drude-Sommerfeld Model, where I show a new definition of heat capacity, among other things.

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Re: Mathis on Graphene? Any hints?

Post by Cr6 on Sun Sep 06, 2015 12:33 am

Also possibly relevant is this piece on "Han Purple" losing the third dimension like mono-layer Graphene. Like Graphene the "magnetism" changes as the temperature changes with barium copper silicate:
--------------

Han Purple and the Third Dimension

Barium copper-silicate doesn't just have archaeologists and chemists intrigued. At normal temperatures, it's an insulator and is nonmagnetic. Along with its many fine properties - prettiness, historical importance, a hint of aristocratic style — barium copper-silicate has many electrons, some of which spin up and some of which are spin down.

Something unusual happens as the temperature drops and as a magnetic field is applied, although the temperature has to drop pretty far, going down to between one and three degrees Kelvin, and the magnetic field has to be about 800,000 times the strength of Earth's magnetic field. The results are worth it — the electrons seem to merge, taking on one spin, and acting as one electron.

That sounds like an ordinary superconductor, you say. Then you're as foolish as a Phoenician in sub-par purple! Han purple still has a trick up its sleeve. Drop the temperature some more and something happens to the magnetic wave traveling through the substance. At higher temperatures, it propagates like a regular wave, traveling in three dimensions. Get under one degree Kelvin, and it no longer has a vertical component. It propagates in two dimensions only.

Scientists think that this has something to do with the structure of barium copper silicate. It's components are arranged like layers of tiles, so they don't stack up neatly. Each layers' tiles are slightly out of sync with the layer below them. This may frustrate the wave and force it to go two dimensional.

http://milesmathis.the-talk.net/n48-new-findings-to-be-explained-with-the-charge-field

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Re: Mathis on Graphene? Any hints?

Post by Cr6 on Mon Sep 07, 2015 12:29 am

Team finds electricity can be generated by dragging saltwater over graphene
April 16, 2014 by Bob Yirka report

Read more at: http://phys.org/news/2014-04-team-electricity-saltwater-graphene.html#jCp
http://phys.org/journals/nature-nanotechnology/
http://www.nature.com/articles/nnano.2014.56
http://www.iflscience.com/technology/tweaked-graphene-could-double-electricity-generated-solar

Illustration of the experimental set-up. A liquid droplet is sandwiched between graphene and a SiO2/Si wafer, and drawn by the wafer at specific velocities. Inset: a droplet of 0.6 M NaCl solution on a graphene surface with advancing and receding contact angles of 91.98 and 60.28, respectively. Credit: Nature Nanotechnology (2014) doi:10.1038/nnano.2014.56

Read more at: http://phys.org/news/2014-04-team-electricity-saltwater-graphene.html#jCp

-------

(Phys.org) —A team of researchers at China's Nanjing University of Aeronautics and Astronautics, studying graphene properties, has discovered that the act of dragging saltwater over a piece of graphene can generate electricity. In their paper published in the journal Nature Nanotechnology, the team describes how in seeking to turn the idea of submerging carbon nanotubes in a flowing liquid to generate a voltage on its head, they came upon the idea of simply dragging water droplets across graphene instead.

Because of graphene's unique electrical properties, researchers have been hard at work trying to determine if it can be used to generate electricity at a lower cost (and in cleaner fashion) than conventional methods. To date, scientists have been using a technique whereby ionic fluids are pushed through different types of nanostructures—it works, but a pressure gradient must be used, which causes the approach to be inefficient. Others have looked at putting carbon nanotubes in moving water to capture electricity that is generated, but once again, a pressure gradient is needed. In this new effort, the researchers have found a way to generate electricity using graphene without the need for a pressure gradient, or any other mechanism other than gravity.

In their experiments, the researchers placed single drops of sea water (and other ionic solutions) on top of strips of monolayer graphene and then dragged them around. Doing so, they discovered, resulted in the generation of electricity—adding more drops or increasing the velocity of dragging increased the voltage.

To understand why, the team took a closer look. As it turned, out, the explanation was simple. When a saltwater drop sits still on top of a strip of graphene, any charge is redistributed symmetrically on both sides of the drop, leaving zero net potential difference between them. When the drop is moved, however, the distribution becomes unbalanced—electrons are desorbed at one end of the drop and absorbed at the other, generating a small amount of voltage—just 30mV—enough to allow the team to use it as part of a handwriting sensor and as part of an energy harvesting device.

Using the newly discovered technique to generate electricity isn't going to become a commercial proposition anytime soon, of course, as there is still the tricky problem of creating mass amounts of graphene at a reasonable price. But if that ever happens, people everywhere could very easily create their own electricity, as it appears the process is exceptionally scalable.

Explore further: Graphene battery demonstrated to power an LED

More information: Generating electricity by moving a droplet of ionic liquid along graphene, Nature Nanotechnology (2014) DOI: 10.1038/nnano.2014.56

Abstract
Since the early nineteenth century, it has been known that an electric potential can be generated by driving an ionic liquid through fine channels or holes under a pressure gradient. More recently, it has been reported that carbon nanotubes can generate a voltage when immersed in flowing liquids, but the exact origin of these observations is unclear, and generating electricity without a pressure gradient remains a challenge. Here, we show that a voltage of a few millivolts can be produced by moving a droplet of sea water or ionic solution over a strip of monolayer graphene under ambient conditions. Through experiments and density functional theory calculations, we find that a pseudocapacitor is formed at the droplet/graphene interface, which is driven forward by the moving droplet, charging and discharging at the front and rear of the droplet. This gives rise to an electric potential that is proportional to the velocity and number of droplets. The potential is also found to be dependent on the concentration and ionic species of the droplet, and decreases sharply with an increasing number of graphene layers. We illustrate the potential of this electrokinetic phenomenon by using it to create a handwriting sensor and an energy-harvesting device.

Journal reference: Nature Nanotechnology

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Re: Mathis on Graphene? Any hints?

Post by Cr6 on Mon Sep 07, 2015 12:32 am

Graphene Could Double Electricity Generated From Solar

January 26, 2015 | by Lisa Winter
Photo credit: scanrail/iStockphoto

The amount of sunlight that hits the Earth every 40 minutes is enough to meet global energy demands for an entire year. The trick, of course, is harnessing it and converting it into useful electricity. A new study has revealed that tweaking graphene allows it to generate two electrons for every photon of light it receives. This could double the amount of electricity currently converted in photovoltaic devices. Marco Grioni from École Polytechnique Fédérale de Lausanne (EPFL) in Switzerland is one of the senior authors on the paper, which was published in Nano Letters.

Graphene is a monolayer of carbon atoms arranged in a honeycomb pattern. It is incredibly light, flexible, exponentially stronger than steel, and capable of conducting electricity even better than copper. In order to make it useful in photovoltaic devices, the researchers needed to have a better idea of graphene’s mechanism for converting light into electricity. This process takes only a femto-second (10-15 sec), which is too quick to easily study.

To learn more about how this energy conversion takes place, the graphene was subjected to a treatment called “ultrafast time- and angle-resolved photoemission spectroscopy” (trARPES). The material was placed in an ultra-high vacuum chamber and blasted with ultrafast laser light, which excited the electrons and made them more capable of carrying an electrical current. A second laser emitted pulses of light, recording the current energy level of each electron in each pulse. These images were then put together, kind of like a flip book, to portray the action that happens on such a short timescale.

The researchers facilitated the conversion process by ‘doping’ the graphene. That is, they improved the material’s photovoltaic prowess by chemically altering the number of electrons, thereby exciting them. When a photon comes and knocks an electron back to the ground state, that one electron is able to excite two more, generating the electric current.

“This indicates that a photovoltaic device using doped graphene could show significant efficiency in converting light to electricity,” says Marco Grioni.

Doped graphene appears to be a great material to easily release the electrons and use extra energy to excite other electrons, rather than waste the energy as heat. Unfortunately, the material needs a little help in absorbing light; a key requirement for photovoltaic devices. Graphene will need to be combined with other ultra-thin materials, such as tungsten diselenide or molybednium disulphide, like has been attempted in previous studies. This could possibly be the key in bumping solar energy conversion from its assumed plateau of 32% up to an astonishing 60%; an increase that could revolutionize solar energy. Moving forward, the researchers are planning to use similar measures to investigate the photovoltaic properties of other ultra-thin materials, including molybednium disulphide.

[Hat tip: EEE Spectrum]

http://www.iflscience.com/technology/tweaked-graphene-could-double-electricity-generated-solar

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Re: Mathis on Graphene? Any hints?

Post by Cr6 on Tue Sep 08, 2015 1:27 am

Found some interesting papers on the Hall effect at Room temperature with Graphene.  Miles had a paper back in July on the Hall Effect.  I think a good student of Mathis can crack this particular nut wide open:

The Hall Effect: a Charge Field Explanation.
I ditch electron holes, offering a logical and mechanical theory for the Hall Voltage.
http://milesmathis.com/hall.pdf
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The Quantum Hall Effect in Graphene
Daniel  G.  Flynn
Department of Physics, Drexel University, Philadelphia, PA
(Dated:  December 7, 2010)
http://www.physics.drexel.edu/~bob/TermPapers/Flynn_QuantumPaper.pdf (an interesting read).

Flynn wrote:
THE QUANTUM HALL EFFECT IN GRAPHENE

GRAPHENE

Graphene  is  a  single  layer  of  carbon  atoms  in  a
two-dimensional  hexagonal  lattice.   The  carbon  atoms
bond  to  one  another  via  covalent  bonds  leaving  one
2p  electron  per  carbon  atom  unbonded.   The  result  is
that  the  Fermi  surface  of  graphene  is  characterized  by
six  double  cones.   In  the  absence  of  applied  fields,  the
Fermi level is situated at the connection points of these
cones.  Since the density of electrons is zero at the Fermi
level,  the  electrical  conductivity  of  graphene  is  very
low.    However,  the  application  of  an  external  electric
field  can  change  the  Fermi  level  causing  graphene  to
behave as a semi-conductor.  In this case, near the Fermi
level  the  dispersion  relation  for  electrons  is  linear  and
the electrons behave as though they have zero effective
mass  (Dirac  fermions).   Because  graphene  exhibits  this
behavior  even  at  room  temperature,  it  is  observed  to
exhibit  both  the  integer  and  fractional  quantum  Hall
effect.

http://www.researchgate.net/publication/6501256_Room-Temperature_Quantum_Hall_Effect_in_Graphene

Quantum Hall Effect Observed At Room Temperature

Date:   February 16, 2007
Source: National High Magnetic Field Laboratory

Summary:
An international team of scientists is able to see the "shimmering quantum world" at ambient temperatures with the help of high magnetic fields and a fascinating material called graphene.

K.S. Novoselov1, Z. Jiang2, 3, Y. Zhang2, S.V. Morozov1, H.L. Storm er2, U. Zeitler4, J.C. Maan4, G.S. Boebinger3, P. Kim2* & A.K. Geim1*
1Departm ent of Physics, University of Manchester, M13 9PL, Manchester, UK
2Departm ent of Physics, Colum bia University, New York, New York 10027, USA
3National High Magnetic Field Laboratory, Tallahassee, Florida 32310, USA
4High Filed Magnet Laboratory, Radboud University Nijmegen, 6525 ED Nijmegen, Netherlands

Using the highest magnetic fields in the world, an international team of researchers has observed the quantum Hall effect -- a much studied phenomenon of the quantum world -- at room temperature.

The quantum Hall effect was previously believed to only be observable at temperatures close to absolute zero (equal to minus 459 degrees). But when scientists at the National High Magnetic Field Laboratory in the U.S. and at the High Field Magnet Laboratory in the Netherlands put a recently developed new form of carbon called graphene in very high magnetic fields, scientists were surprised by what they saw.

"At room temperature, these electron waves are usually destroyed by the jiggling atoms and the quantum effects are destroyed," said Nobel Prize winner Horst Stormer, physics professor at Columbia University and one of the paper's authors. "Only on rare occasions does this shimmering quantum world survive to the temperature scale of us humans."

The quantum Hall effect is the basis for the international electrical resistance standard used to characterize even everyday materials that conduct electricity, such as the copper wires in a home. It was first discovered in 1980 by the German physicist Klaus von Klitzing, who was awarded a Nobel Prize in 1985 for his discovery. Until recently the quantum Hall effect was considered to belong to the realm of very low temperatures.

That opinion began to change, however, with the ability to create very high magnetic fields and with the discovery of graphene, a single atomic sheet of atoms about as strong as diamond. Together, these two things have allowed scientists to push this fragile quantum effect all the way to room temperature. Now there is a way to see curious and often surprising quantum effects, such as frictionless current flow and resistances as accurate as a few parts per billion, even at room temperature.

The research was carried out by scientists from the University of Manchester in England, Columbia University in New York, the National High Magnetic Field Laboratory in Tallahassee, Florida, the High Field Magnet Laboratory in Nijmegen, Netherlands, and the Foundation for Fundamental Research on Matter, also in the Netherlands. Their article appears in Science Express, the advanced online publication of Science magazine, a top American journal with international stature.

The scientists believe that these findings may one day lead to a compact resistance standard working at elevated temperatures and magnetic fields that are easily attainable at the National High Magnetic Field Laboratory.

"The more we understand the strange world of quantum physics, the better we can design the next generation of ultra-small electrical devices, which already are pushing into the quantum regime," said Gregory S. Boebinger, director of the U.S. magnet lab.

"This is a really amazing discovery for a quantum Hall physicist," said Uli Zeitler, senior scientist at the High Field Magnet Laboratory. "For more than two decades, we've focused our research on exploring new frontiers such as very low temperatures and extremely sophisticated materials, and now it appears that we can just measure a quantum Hall effect in a pencil-trace and at room temperature."

The room temperature quantum Hall effect was discovered independently in the two high field labs, in the 45-tesla Hybrid magnet in Tallahassee and in a 33-tesla resistive magnet in Nijmegen. Both research groups agreed that a common announcement on both sides of the Atlantic was the right thing to do.

"Because so many scientists are exploring this exciting new material, we are all on this roller coaster together," said Boebinger. "Sometimes it makes sense to put competitiveness aside and write a better paper together."

In addition to Stormer, Boebinger and Zeitler, authors on the paper include Andre Geim and Kostya Novoselov of the University of Manchester; Philip Kim, Zhigang Jiang and Y. Zhang at Columbia, and Jan Kees Maan, director of the High Field Magnet Lab.

This work is supported by the National Science Foundation, the U.S. Department of Energy, the Microsoft Corp., and the W.M. Keck Foundation.

The National High Magnetic Field Laboratory develops and operates state-of-the-art, high-magnetic-field facilities that faculty and visiting scientists and engineers use for research. The laboratory is sponsored by the National Science Foundation and the state of Florida. To learn more, visit http://www.magnet.fsu.edu.



Also:
--------

Operation of graphene quantum Hall resistance standard in a cryogen-free table-top system

"One of the first properties observed in graphene was the QHE and it was immediately realised that it is ideal for metrology by virtue of its unique band structure [4] [5] [6] [7]. The Landau level quantisation in graphene is a lot stronger than in traditional semiconductor systems which implies that both a lower magnetic field can be used and that the low temperature constraint is more relaxed [6]. Following the original demonstration of high-accuracy quantum Hall resistance measurements in epitaxial graphene grown on SiC [8] and proof of the universality of the QHE between graphene and GaAs [9], recently these results have been very nicely reproduced by a number of different research groups [10] [11] [12]. "  

Operation of graphene quantum Hall resistance standard in a cryogen-free table-top system

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Re: Mathis on Graphene? Any hints?

Post by Cr6 on Tue Sep 08, 2015 1:50 am

Highly compressible 3D periodic graphene aerogel microlattices
http://www.nature.com/ncomms/2015/150422/ncomms7962/full/ncomms7962.html

Posted: Feb 09, 2015
3D-printing with graphene

(Nanowerk Spotlight) The successful implementation of graphene-based devices invariably requires the precise patterning of graphene sheets at both the micrometer and nanometer scale. It appears that 3D-printing techniques are an attractive fabrication route towards three-dimensional graphene structures. In a previous Nanowerk Spotlight we reported on the first 3D printed nanostructures made entirely of graphene.

There are also different methods to build 3D graphene monoliths – for example freeze casting or emulsion templating, etc. – but they are limited to building simple shapes, for example cylinders or cubes.



Using a different approach, researchers have now used flakes of chemically modified graphene – namely graphene oxide GO and its reduced form rGO – together with very small amounts of a responsive polymer (a polymer that changes behavior and conformation when a 'chemical switch' is activated), to formulate water based ink or pastes.
"Our formulations have the flow and physical properties we need for the filament deposition process required in 3D printing: They need to flow through very small nozzles and set immediately after passing through it, retaining the shape and holding the layers on top," Dr. Esther García-Tuñon, a Research Associate at the Centre for Advanced Structural Ceramics at Imperial College London (ICL), tells Nanowerk. "We use this two-dimensional material as building block to create macroscopic 3D structures and a technique called direct ink writing (DIW) also known as direct write assembly (DWA), or Robocasting."

http://www.nanowerk.com/spotlight/spotid=38965.php

García-Tuñon is first author of a paper in the January 21, 2015 online edition of Advanced Materials ("Printing in Three Dimensions with Graphene") where a team from ICL, the University of Warwick, the University of Bath, and the Universidad de Santiago de Compostela, describe their technique.

This technique is based on the continuous deposition of a filament following a computer design. The 3D structures are built layer by layer from bottom to top.

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Re: Mathis on Graphene? Any hints?

Post by Cr6 on Wed Sep 09, 2015 11:56 pm

Electronic transport in graphene: towards high mobility  
K.   I.     BOLOTIN    ,     Vanderbilt  University ,   USA    
DOI:  10.1533/9780857099334.3.1991999
© 2014 Woodhead Publishing Limited

Abstract:   Strong carrier scattering perturbs the intrinsic response of
Dirac fermions in graphene and limits potential applications of
graphene-based devices. Multiple scattering mechanisms including
Coulomb scattering, lattice disorder scattering and electron–phonon
scattering play roles in realistic graphene devices. Moreover, different
types and preparations of graphene are characterized by different
dominant scattering mechanisms. In this chapter, we review the recent
progress towards reduction of carrier scattering in graphene. We start by
discussing different metrics – such as carrier mobility, mean free path,
and scattering time – that are used to quantify the scattering strength.
Then, we review the strategies to reduce scattering and to improve
carrier mobility. These strategies include: lowering defect density,
suspending graphene, depositing graphene onto high-quality substrates,
and covering it with high- k dielectrics. Finally, we briefl y address the
physical phenomena and device applications that are specific to
ultraclean high-mobility graphene.  

http://scitechconnect.elsevier.com/wp-content/uploads/2014/06/Graphene-Skakalova-ch9.pdf

210 Graphene
9.4.3
Electron–phonon scattering
---------------
Quantum Hall conductance of graphene combined with charge-trap memory operation

Haeyong Kang1,3, Yoojoo Yun1,3, Jeongmin Park1, Joonggyu Kim1, Thuy Kieu Truong1, Jeong-Gyun Kim1, Nahee Park1, Hoyeol Yun2, Sang Wook Lee2, Young Hee Lee1 and Dongseok Suh1

Published 5 August 2015 • © 2015 IOP Publishing Ltd • Nanotechnology, Volume 26, Number 34

Abstract

The combination of quantum Hall conductance and charge-trap memory operation was qualitatively examined using a graphene field-effect transistor. The characteristics of two-terminal quantum Hall conductance appeared clearly on the background of a huge conductance hysteresis during a gate-voltage sweep for a device using monolayer graphene as a channel, hexagonal boron-nitride flakes as a tunneling dielectric and defective silicon oxide as the charge storage node. Even though there was a giant shift of the charge neutrality point, the deviation of quantized resistance value at the state of filling factor 2 was less than 1.6% from half of the von Klitzing constant. At high Landau level indices, the behaviors of quantum conductance oscillation between the increasing and the decreasing electron densities were identical in spite of a huge memory window exceeding 100 V. Our results indicate that the two physical phenomena, two-terminal quantum Hall conductance and charge-trap memory operation, can be integrated into one device without affecting each other.

https://iopscience.iop.org/article/10.1088/0957-4484/26/34/345202/pdf

A NIST paper on the Hall Effect:
---------

Developing a 'Gold Standard' for Hall Resistance

April 7, 2014

*
Contact: Rand Elmquist
(301) 975-6591

close-up of Hall bar and contacts

Configuration of the QHE device showing dimensions. The blue-gray rectangle in the center is the open face of the Hall bar. The locations of graphene components are outlined by white lines. Source and drain are at the left and right ends of the bar. There are electrical contacts above and below the bar. Click on image for enlarged view.
PML researchers have developed a novel method of fabricating graphene-based microdevices that may hasten the arrival of a new generation of standards for electrical resistance. The new design offers substantial performance enhancement over most existing devices, and can be adjusted to produce a wide range of electronic properties.

Since 1990, the internationally accepted means of realizing the ohm has been based on the quantum Hall effect* (QHE), in which resistance is exactly quantized in increments dictated by constants of nature. The QHE is measured using electrical contacts placed along the sides of a rectangular, cryogenically cooled, current-bearing conductor (the “Hall bar”) in which the charge carriers behave like a two-dimensional (2D) gas.

Charge carriers then condense at one or more energy levels in a strong magnetic field, and this produces resistance plateaus. The widely-used standards for such measurements are based on GaAs/AlGaAs heterostructure devices and require high magnetic field strengths in the range of 5 tesla (T) to 15 T, typically obtainable only with expensive superconducting magnets.

When QHE was first observed in graphene ten years ago, the inherently 2D material became a prime candidate for realizing the quantized Hall resistance (QHR) standard because QHE plateaus could be observed in graphene at lower magnetic field strength and higher temperature than in semiconductor devices.

In general, there are three ways to obtain monolayer graphene sheets suitable to that task: the sticky-tape “exfoliation” method used in 2004 to isolate the material for the first time; chemical vapor deposition on copper or other material; and growth on an insulating silicon carbide substrate, which the PML researchers employ.**

No matter how it is obtained, however, incorporating graphene into a practical standard entails the same sort of lithographic techniques used to fabricate most microstructures: features are created by spin-coating a polymer-based liquid over a surface, drying it, and exposing certain regions of the sample to light or to an electron beam to form masks for etching.

“There are serious difficulties when working on graphene in that environment,” says physicist Rand Elmquist of the Quantum Measurement Division. “Being an open surface, graphene is very sensitive to chemicals in the air or from materials it contacts. In normal photolithography or electron-beam lithography, the fabrication process lays down organic compounds – the liquid resist – onto whatever material is being treated. Those organic compounds leave a residue on graphene that won’t come off, creating imperfections in surfaces and contacts that can affect the electronic behavior.

“So we came up with a new way to make devices that we hoped would produce better contacts, and also keep the graphene clean, and free of organic contamination.”

This method, developed at PML by physicist Yanfei Yang involves coating a sheet of graphene on a section of silicon carbide wafer with about 15 nanometers of gold before any lithography. Patterns are developed using traditional photolithography to remove any unwanted gold-coated graphene. Then, the areas that will be the Hall bar contacts get a thicker coating of gold, so that they will make good connections for wires used in electrical measurements. In the last step, the gold layer over the area of graphene that will serve as the Hall bar is removed with dilute aqua regia, a mixture of nitric acid, hydrochloric acid, and deionized water, leaving the graphene almost completely clean.



“To our surprise,” says Elmquist of the Fundamental Electrical Measurements Group, “we found that aqua regia etching produces helpful p-type doping in the graphene.” That is, molecules from the acids stick to the surface, reducing the carrier density and improving the mobility of electrons that remain. Low carrier density is important because the higher the density of charge-carriers in the Hall bar, the higher the magnetic field strength required to observe the critical QHE plateaus.

“Normal epitaxial graphene (EG) grown on SiC has an electron density of 1013 per square centimeter,” Elmquist says. “At that level, you can’t see the QHE”; doing so would require a magnetic field strength far too high to be used in a working standard. “As a practical matter, you need to get down to around 5 x 1011 per cm2 or lower for use at reasonable field strength.”

By contrast, the PML group’s new EG devices were shown to have carrier densities in the range of 3 x 1010 per cm2 to 3 x 1011 per cm2, allowing observation of clearly defined resistance quantization at magnetic field strengths of less than 4 T. The p-type molecular doping effect can be reduced by heating in argon gas, and is restored by dipping in aqua regia.

The team has submitted its results for publication in the journal Advanced Materials. But there is much more to learn. “One thing we are working on is a better understanding of how the QHE develops in graphene, and specific features of the QHE that occur nowhere else” Elmquist says; “One day soon we hope to implement this or a similar method to make nearly perfect graphene QHR devices that surpass the best grown with GaAs.”

* The Hall effect occurs when current traveling through a conductor is exposed to a magnetic field oriented at a 90-degree angle to the current flow. Because of the effect of the field on the charge carriers, electron (or hole) populations are higher on one side of the conductor and lower on the other. This produces a transverse voltage that is perpendicular to both the current flow and the field. At the quantum level, the effect is exactly quantized, and resistance – as determined by the ratio of transverse voltage to current – is thus also quantized.

** The PML group makes epitaxial graphene (EG) by heating a crystal of SiC to as high as 2100 ͦC. Silicon on the outermost surface turns to gas. The remaining carbon atoms arrange themselves into hexagonal units and form a sheet of graphene atop and aligned with the underlying crystal. The EG process has advantages for making devices compared to the other two familiar sources of graphene. Exfoliation of graphite produces sheets with dimensions in the range of tens of micrometers – too small for many uses. And graphene grown by chemical vapor deposition has to be removed from its metal substrate and transferred elsewhere, whereas EG can be used as formed. One drawback to the technique is that the EG layers are doped by the formation of covalent bonds with the underlying crystal and have high electron densities.

The collaboration includes researchers now at Georgetown University and institutions in Japan, Taiwan, and Argentina.

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Re: Mathis on Graphene? Any hints?

Post by Nevyn on Thu Sep 10, 2015 1:36 am

You have managed to perform a monumental research effort here, Cr6. Every time I read these posts I want to get in and model something but I am tied into other projects at the moment and can't really fit another one in. Very interesting stuff.
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Re: Mathis on Graphene? Any hints?

Post by Cr6 on Sun Sep 13, 2015 12:21 am

Nevyn wrote:You have managed to perform a monumental research effort here, Cr6. Every time I read these posts I want to get in and model something but I am tied into other projects at the moment and can't really fit another one in. Very interesting stuff.


Thanks Nevyn,

I just found these articles of interest around graphene's diverse properties. I kind of figure that Mathis' work will eventually provide the most comprehensive explanation.  Your work is fantastic on the viewers.  Just really cool and interesting. I understand priorities in development so go with what you see as the most necessary.  I kind of figured that graphene is going to get "huge" attention in the nano-tech world in the future.  It is best we see it from a Mathis' point of view.

Here's an article on Graphene and "spasers" and "Plasmons" (I bet Mathis could provide us with some clues on this eventually)... it looks like a pretty promising approach to cancer treatments:
--------
Death Ray 'Spasers' Kill Cancer
Nov 4, 2014 01:00 PM ET // by Neil Savage, IEEE Spectrum
http://spectrum.ieee.org/

http://news.discovery.com/tech/nanotechnology/death-ray-spasers-kill-cancer-141104.htm

Encircling tumors with a phalanx of miniature lasers could offer a new way to battle cancer, a team of Australian researchers is proposing.

Technically, the proposed device isn’t really a laser at all, but a spaser, with surface plasmons rather than light undergoing amplification.
How Nanotech Can Make A Better You: Photos

Plasmons are oscillations in electron density created in the surface of a small metal object when photons strike it. It’s possible to design a device so that the plasmons feed back on themselves, amplifying in much the same way photons bouncing around a laser cavity stimulate the emission of other photons, creating laser light.

“The spaser is basically the same as a laser,” says Chanaka Rupasinghe, a postgraduate student in electrical and computer engineering at Monash University near Melbourne, Australia. He and his professor, Malin Premaratne, presented their idea in a paper at the recent IEEE Photonics Conference, in Los Angeles.

Spasers have been built of gold nanoparticles surrounded by a silica shell and from cadmium sulfide nanowires on a silver substrate. Earlier this year, Rupasinghe and Premaratne proposed a different design, using graphene and carbon nanotubes.

In their setup, a carbon nanotube would absorb the energy from a separate laser source and transfer it to the surface plasmons of a nearby nanoflake of graphene, creating the spaser effect. Pumping the spaser with 1200-nanometer light would cause it to output light at 1700 nm, Rupasinghe says. They argued their spaser would be mechanically strong but flexible, chemically and thermally stable, and compatible with biomedical applications.

Once they had their design, their next idea was to use it to replace some of the nanoparticles already being explored as cancer treatments that are being designed to deliver drugs directly to tumors. The nanotubes and graphene flakes could have antibodies or ligands attached to them that would draw them to the tumor. Once at the tumor, they’d self-assemble into an array of spasers.

“You surround cancer cells with very tiny lasers, instead of nanoparticles,” Rupasinghe says.
Can Bras Cause Cancer?

An external laser producing light between 1000 and 1350 nm could penetrate several centimeters of human tissue and act as a power source for the spaser array. The spasers would then deliver a concentrated blast of heat to the cancer cells. At the same time, Rupasinghe says, the nanotubes could be designed to carry drugs to their target, hitting the tumor with a one-two punch.

No one has yet built the graphene-nanotube spasers, let alone started the long process to see whether they’d make a safe and effective cancer treatment. “Our team is basically a theoretical and modelling group,” Rupasinghe says. But his hope is that this idea may someday provide another weapon in the anti-tumor arsenal.

Get more from IEEE Spectrum

This article originally appeared on IEEE Spectrum; all rights reserved.

http://news.discovery.com/tech/nanotechnology/death-ray-spasers-kill-cancer-141104.htm
----------


Graphene- carbon nanotube spaser nanolaser introduced
We have been able to design the world's first 'spaser' - a nanoscale laser - made out of graphene and carbon. A spaser (surface plasmon amplication by stimulated emission of radiation) is effectively a nanoscale laser, or a nanonlaser. It has been touted as the future of optical computers and technologies. It could enable ‘nanophotonic’ circuitry, extremely small circuits far tinier than anything available today. This could usher in many technological advances including microchips hundred times more powerful than anything we have today.

'Our device would be comprised of a graphene resonator and a carbon nanotube gain element.'

'The use of carbon means our spaser would be more robust and flexible, would operate at high temperatures, and be eco-friendly'

See dailymail.co.uk article for more information
http://www.dailymail.co.uk/sciencetech/article-2614883/Your-T-shirt-ringing-Mobile-phones-soon-built-CLOTHES-thanks-breakthrough-tiny-microchips.html
http://www.chanakarupasinghe.com/

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Re: Mathis on Graphene? Any hints?

Post by Cr6 on Tue Sep 15, 2015 10:31 pm

'Simple, green, and cost-effective' method of graphene production announced

   Ben Coxworth
   June 21, 2011


http://www.gizmag.com/graphene-production-magnesium-dry-ice/18986/



Graphene, the one-atom-thick carbon sheet material that could revolution everything from energy storage to computer chips, can now be made much more easily - at least, that's what scientists from Northern Illinois University (NIU) are telling us. While previous production methods have included things like repeatedly splitting graphite crystals with tape, heating silicon carbide to high temperatures, and various other approaches, the latest process simply involves burning pure magnesium in dry ice.

The graphene created consists of several layers - not just one - although it is still less than ten atoms thick.

"It is scientifically proven that burning magnesium metal in carbon dioxide produces carbon, but the formation of this carbon with few-layer graphene as the major product has neither been identified nor proven as such until our current report," said Narayan Hosmane, an NIU professor of chemistry and biochemistry, and leader of the project. "The synthetic process can be used to potentially produce few-layer graphene in large quantities. Up until now, graphene has been synthesized by various methods utilizing hazardous chemicals and tedious techniques. This new method is simple, green and cost-effective."

Hosmane's team had set out to produce single-wall carbon nanotubes, and inadvertently discovered the graphene-production method in the process.

The research was recently published in the Journal of Materials Chemistry.

Last November, researchers from Rice University announced another promising graphene production method, that utilizes simple table sugar.

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Re: Mathis on Graphene? Any hints?

Post by Cr6 on Tue Sep 15, 2015 10:35 pm


Journal of Physics: Condensed Matter


Graphene grown on magnesium oxide has a band gap


Can graphene/MgO heterojunctions be the basis for graphene transistors on Si(100)?

1.5 monolayer graphene film grown by PVD on MgO(111).

Graphene is an exciting electronic material due to extremely high room temperature mobilities. The lack of a band gap and the inability to grow graphene directly on dielectric substrates has hindered the development of practical graphene logic devices on Si. Graphene has now been grown by direct chemical and physical vapour deposition on MgO(111). Graphene/MgO interactions destroy the chemical equivalency of adjacent graphene sites, thus opening a band gap of around 0.5–1 eV. Since MgO(111) films have been grown on Si(100), a graphene/MgO/Si(100) transistor is a possibility.

The finding that electrons in graphene layers behave as massless fermions has opened broad new possibilities for truly disruptive, ultrafast graphene-based electronic devices. Two major obstacles, however, have blocked the development of practical graphene devices integrated with Si CMOS: (a) the inability to grow graphene layers on dielectric substrates by practical, scalable methods, such as chemical or physical vapor deposition, and (b) the absence of a graphene band gap, which hinders logic device applications. New work has demonstrated that graphene films can be deposited by chemical or physical vapor deposition (CVD, PVD) on MgO(111), and that a 2.5 monolayer-thick graphene film on MgO(111) displays a band gap, suitable for logic applications.

In recent work published in J. Phys.: Condens. Matter 23 072204, the low energy electron diffraction (LEED) intensities of graphene films deposited by CVD or PVD were analyzed, and shown to display three-fold, rather than six-fold symmetry. The data demonstrate that adjacent atoms on the graphene lattice are no longer chemically equivalent, thus lifting the highest occupied/lowest unoccupied molecular orbital (HOMO/LUMO) degeneracy at the Dirac point and opening a band gap. The data also strongly suggest that the size of the band gap decreases with an increasing number of graphene layers. While the electron transport characteristics of graphene films on MgO have yet to be determined, the ability to systematically vary the number of graphene layers should permit 'tuning' of band gap and charge transport properties. Since the growth of MgO(111) films on Si(100) has been reported, there now exists a potential direct route towards the formation of graphene transistors on Si(100).

https://iopscience.iop.org/0953-8984/labtalk-article/45265

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Re: Mathis on Graphene? Any hints?

Post by Cr6 on Sat Mar 11, 2017 9:30 pm



Graphene Effectively Filters Electrons According to the Direction of Their Spin
December 26, 2013

New research from MIT shows that graphene can effectively filter electrons according to the direction of their spin, something that cannot be done by any conventional electronic system.

Graphene has become an all-purpose wonder material, spurring armies of researchers to explore new possibilities for this two-dimensional lattice of pure carbon. But new research at MIT has found additional potential for the material by uncovering unexpected features that show up under some extreme conditions — features that could render graphene suitable for exotic uses such as quantum computing.

The research is published this week in the journal Nature, in a paper by professors Pablo Jarillo-Herrero and Ray Ashoori, postdocs Andrea Young and Ben Hunt, graduate student Javier Sanchez-Yamaguchi, and three others. Under an extremely powerful magnetic field and at extremely low temperature, the researchers found, graphene can effectively filter electrons according to the direction of their spin, something that cannot be done by any conventional electronic system.

Under typical conditions, sheets of graphene behave as normal conductors: Apply a voltage, and current flows throughout the two-dimensional flake. If you turn on a magnetic field perpendicular to the graphene flake, however, the behavior changes: Current flows only along the edge, while the bulk remains insulating. Moreover, this current flows only in one direction — clockwise or counterclockwise, depending on the orientation of the magnetic field — in a phenomenon known as the quantum Hall effect.

In the new work, the researchers found that if they applied a second powerful magnetic field — this time in the same plane as the graphene flake — the material’s behavior changes yet again: Electrons can move around the conducting edge in either direction, with electrons that have one kind of spin moving clockwise while those with the opposite spin move counterclockwise.

“We created an unusual kind of conductor along the edge,” says Young, a Pappalardo Postdoctoral Fellow in MIT’s physics department and the paper’s lead author, “virtually a one-dimensional wire.” The segregation of electrons according to spin is “a normal feature of topological insulators,” he says, “but graphene is not normally a topological insulator. We’re getting the same effect in a very different material system.”

What’s more, by varying the magnetic field, “we can turn these edge states on and off,” Young says. That switching capability means that, in principle, “we can make circuits and transistors out of these,” he says, which has not been realized before in conventional topological insulators.

There is another benefit of this spin selectivity, Young says: It prevents a phenomenon called “backscattering,” which could disrupt the motion of the electrons. As a result, imperfections that would ordinarily ruin the electronic properties of the material have little effect. “Even if the edges are ‘dirty,’ electrons are transmitted along this edge nearly perfectly,” he says.

Jarillo-Herrero, the Mitsui Career Development Associate Professor of Physics at MIT, says the behavior seen in these graphene flakes was predicted, but never seen before. This work, he says, is the first time such spin-selective behavior has been demonstrated in a single sheet of graphene, and also the first time anyone has demonstrated the ability “to transition between these two regimes.”

That could ultimately lead to a novel way of making a kind of quantum computer, Jarillo-Herrero says, something that researchers have tried to do, without success, for decades. But because of the extreme conditions required, Young says, “this would be a very specialized machine” used only for high-priority computational tasks, such as in national laboratories.

Ashoori, a professor of physics, points out that the newly discovered edge states have a number of surprising properties. For example, although gold is an exceptionally good electrical conductor, when dabs of gold are added to the edge of the graphene flakes, they cause the electrical resistance to increase. The gold dabs allow the electrons to backscatter into the oppositely traveling state by mixing the electron spins; the more gold is added, the more the resistance goes up.

This research represents “a new direction” in topological insulators, Young says. “We don’t really know what it might lead to, but it opens our thinking about the kind of electrical devices we can make.”

The experiments required the use of a magnetic field with a strength of 35 tesla — “about 10 times more than in an MRI machine,” Jarillo-Herrero says — and a temperature of just 0.3 degrees Celsius above absolute zero. However, the team is already pursuing ways of observing a similar effect at magnetic fields of just one tesla — similar to a strong kitchen magnet — and at higher temperatures.

(More at link:
http://scitechdaily.com/graphene-effectively-filters-electrons-according-direction-spin/
)

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Re: Mathis on Graphene? Any hints?

Post by Cr6 on Sun Apr 16, 2017 11:36 pm

Could ‘miracle’ material graphene finally have a use by making seawater drinkable?

Published time: 4 Apr, 2017 15:52

Water, water everywhere, but not a drop to drink? The Rime of the Ancient Mariner may soon be left redundant now that scientists have devised a sieve made of ‘miracle material’ graphene capable of removing salt molecules from seawater, rendering it safe to drink.

When it was discovered by Andre Geim and his colleague Konstantin Novoselov, physics professors working at Manchester University around 2004, graphene was hailed as a ground-breaking discovery, with the media calling it a “wonder material.”
...more at link

Nair stressed the importance of the pores being just the right size to capture the salt molecules while releasing the water ones.

“To make it permeable, you need to drill small holes in the membrane.

“But if the hole size is larger than one nanometre, the salts go through that hole.

“You have to make a membrane with a very uniform less-than-one-nanometre hole size to make it useful for desalination.

“It is a really challenging job,” he added.

The graphene oxide membrane previously showed signs of swelling when dipped into water, meaning smaller salts could still permeate. By adding walls of epoxy resin on either side of the membrane, however, scientists found they could stop the pores expanding.

“This is our first demonstration that we can control the spacing [of pores in the membrane] and that we can do desalination, which was not possible before.

“The next step is to compare this with the state-of-the-art material available on the market.”

Up to 14 percent of the world’s population will struggle with water supply by 2025, according to the United Nations. WaterAid claims one in 10 people already live without safe water.

As climate change takes its toll, more countries are likely to consider investing in desalination technologies.

Desalination plants currently use polymer-based membranes. However, it is hoped that graphene oxide will prove more efficient, scaling up water distillation around the world, especially in poor regions where such facilities are prohibitively expensive.

Following news of the ground-breaking research, Ram Devanathan, from the Pacific Northwest National Laboratory in Richland, US, said more work needs to be done to produce the membranes inexpensively on an industrial scale.

Writing in the Nature Nanotechnology science journal, Devanathan said: “The selective separation of water molecules from ions by physical restriction of interlayer spacing opens the door to the synthesis of inexpensive membranes for desalination.”

https://www.rt.com/uk/383480-graphene-sieve-drinking-water/
related:
Out of thin air: Scientists create solar powered device turning air into drinking water
Published time: 16 Apr, 2017 04:05
https://www.rt.com/viral/384909-air-water-solar-power/

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Re: Mathis on Graphene? Any hints?

Post by Cr6 on Sun Apr 23, 2017 10:29 pm

Graphene 'copy machine' may produce cheap semiconductor wafers
Engineers use graphene as a 'copy machine' to produce cheaper semiconductor wafers

(more at link...)

Date: April 19, 2017
Source: Massachusetts Institute of Technology
Summary:
A new technique may vastly reduce the overall cost of wafer technology and enable devices made from more exotic, higher-performing semiconductor materials than conventional silicon. The new method uses graphene -- single-atom-thin sheets of graphite -- as a sort of 'copy machine' to transfer intricate crystalline patterns from an underlying semiconductor wafer to a top layer of identical material.

n 2016, annual global semiconductor sales reached their highest-ever point, at $339 billion worldwide. In that same year, the semiconductor industry spent about $7.2 billion worldwide on wafers that serve as the substrates for microelectronics components, which can be turned into transistors, light-emitting diodes, and other electronic and photonic devices.

A new technique developed by MIT engineers may vastly reduce the overall cost of wafer technology and enable devices made from more exotic, higher-performing semiconductor materials than conventional silicon.

The new method, reported in Nature, uses graphene -- single-atom-thin sheets of graphite -- as a sort of "copy machine" to transfer intricate crystalline patterns from an underlying semiconductor wafer to a top layer of identical material.

The engineers worked out carefully controlled procedures to place single sheets of graphene onto an expensive wafer. They then grew semiconducting material over the graphene layer. They found that graphene is thin enough to appear electrically invisible, allowing the top layer to see through the graphene to the underlying crystalline wafer, imprinting its patterns without being influenced by the graphene.

Graphene is also rather "slippery" and does not tend to stick to other materials easily, enabling the engineers to simply peel the top semiconducting layer from the wafer after its structures have been imprinted.

Jeehwan Kim, the Class of 1947 Career Development Assistant Professor in the departments of Mechanical Engineering and Materials Science and Engineering, says that in conventional semiconductor manufacturing, the wafer, once its crystalline pattern is transferred, is so strongly bonded to the semiconductor that it is almost impossible to separate without damaging both layers.

"You end up having to sacrifice the wafer -- it becomes part of the device," Kim says.

With the group's new technique, Kim says manufacturers can now use graphene as an intermediate layer, allowing them to copy and paste the wafer, separate a copied film from the wafer, and reuse the wafer many times over. In addition to saving on the cost of wafers, Kim says this opens opportunities for exploring more exotic semiconductor materials.

"The industry has been stuck on silicon, and even though we've known about better performing semiconductors, we haven't been able to use them, because of their cost," Kim says. "This gives the industry freedom in choosing semiconductor materials by performance and not cost."

Kim's research team discovered this new technique at MIT's Research Laboratory of Electronics. Kim's MIT co-authors are first author and graduate student Yunjo Kim; graduate students Samuel Cruz, Babatunde Alawonde, Chris Heidelberger, Yi Song, and Kuan Qiao; postdocs Kyusang Lee, Shinhyun Choi, and Wei Kong; visiting research scholar Chanyeol Choi; Merton C. Flemings-SMA Professor of Materials Science and Engineering Eugene Fitzgerald; professor of electrical engineering and computer science Jing Kong; and assistant professor of mechanical engineering Alexie Kolpak; along with Jared Johnson and Jinwoo Hwang from Ohio State University, and Ibraheem Almansouri of Masdar Institute of Science and Technology.

Graphene shift

Since graphene's discovery in 2004, researchers have been investigating its exceptional electrical properties in hopes of improving the performance and cost of electronic devices. Graphene is an extremely good conductor of electricity, as electrons flow through graphene with virtually no friction. Researchers, therefore, have been intent on finding ways to adapt graphene as a cheap, high-performance semiconducting material.

"People were so hopeful that we might make really fast electronic devices from graphene," Kim says. "But it turns out it's really hard to make a good graphene transistor."

In order for a transistor to work, it must be able to turn a flow of electrons on and off, to generate a pattern of ones and zeros, instructing a device on how to carry out a set of computations. As it happens, it is very hard to stop the flow of electrons through graphene, making it an excellent conductor but a poor semiconductor.

Kim's group took an entirely new approach to using graphene in semiconductors. Instead of focusing on graphene's electrical properties, the researchers looked at the material's mechanical features.

"We've had a strong belief in graphene, because it is a very robust, ultrathin, material and forms very strong covalent bonding between its atoms in the horizontal direction," Kim says. "Interestingly, it has very weak Van der Waals forces, meaning it doesn't react with anything vertically, which makes graphene's surface very slippery."

Copy and peel

The team now reports that graphene, with its ultrathin, Teflon-like properties, can be sandwiched between a wafer and its semiconducting layer, providing a barely perceptible, nonstick surface through which the semiconducting material's atoms can still rearrange in the pattern of the wafer's crystals. The material, once imprinted, can simply be peeled off from the graphene surface, allowing manufacturers to reuse the original wafer.

The team found that its technique, which they term "remote epitaxy," was successful in copying and peeling off layers of semiconductors from the same semiconductor wafers. The researchers had success in applying their technique to exotic wafer and semiconducting materials, including indium phosphide, gallium arsenenide, and gallium phosphide -- materials that are 50 to 100 times more expensive than silicon.

Kim says that this new technique makes it possible for manufacturers to reuse wafers -- of silicon and higher-performing materials -- "conceptually, ad infinitum."

An exotic future

The group's graphene-based peel-off technique may also advance the field of flexible electronics. In general, wafers are very rigid, making the devices they are fused to similarly inflexible. Kim says now, semiconductor devices such as LEDs and solar cells can be made to bend and twist. In fact, the group demonstrated this possibility by fabricating a flexible LED display, patterned in the MIT logo, using their technique.

"Let's say you want to install solar cells on your car, which is not completely flat -- the body has curves," Kim says. "Can you coat your semiconductor on top of it? It's impossible now, because it sticks to the thick wafer. Now, we can peel off, bend, and you can do conformal coating on cars, and even clothing."

Going forward, the researchers plan to design a reusable "mother wafer" with regions made from different exotic materials. Using graphene as an intermediary, they hope to create multifunctional, high-performance devices. They are also investigating mixing and matching various semiconductors and stacking them up as a multimaterial structure.
...

Story Source:

Materials provided by Massachusetts Institute of Technology. Original written by Jennifer Chu. Note: Content may be edited for style and length.

Journal Reference:

Yunjo Kim, Samuel S. Cruz, Kyusang Lee, Babatunde O. Alawode, Chanyeol Choi, Yi Song, Jared M. Johnson, Christopher Heidelberger, Wei Kong, Shinhyun Choi, Kuan Qiao, Ibraheem Almansouri, Eugene A. Fitzgerald, Jing Kong, Alexie M. Kolpak, Jinwoo Hwang, Jeehwan Kim. Remote epitaxy through graphene enables two-dimensional material-based layer transfer. Nature, 2017; 544 (7650): 340 DOI: 10.1038/nature22053

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Re: Mathis on Graphene? Any hints?

Post by Cr6 on Sat Jun 24, 2017 12:42 am

Laser 3D printing helps Rice, Tianjin researchers create atomically thin graphene

Jun 21, 2017 | By Benedict

Nanotechnologists from Rice University and China’s Tianjin University have used laser 3D printing to fabricate centimeter-sized objects of atomically thin graphene. The research could help create industrial quantities of bulk graphene.

Nickel functions as a catalyst to turn laser-melted sugar into graphene

It’s hardly surprising that graphene, a two-dimensional sheet of pure carbon, is a subject of great interest for materials scientists. Not only is graphene incredibly strong, it’s also conductive, and can therefore be used in a wide range of applications, from nanoelectronics to bone implants.

The challenge is getting reasonably sized quantities of 3D graphene. To do the most useful stuff with the material, bulk quantities are needed, and scientists have so far had trouble making graphene on that scale in an efficient way.

A team of nanotechnologists from Rice University and China’s Tianjin University recently used 3D laser printing to fabricate centimeter-sized objects of atomically thin graphene, in a research project that could someday lead to the simple fabrication of bulk quantities of graphene from non-graphene starting materials.

For the research project, the laboratory of Rice chemist James Tour joined forces with the labs of Rice’s Jun Luo and Tianjin’s Naiqin Zhao to adapt a common 3D printing technique. The technique, conducted at room temperature, was used to make fingertip-size blocks of graphene foam. No molds were required, and the starting materials consisted of just powdered sugar and nickel powder.

3D printing was used to produce a porous graphene foam

“This simple and efficient method does away with the need for both cold-press molds and high-temperature CVD treatment,” said co-lead author Junwei Sha, a former student in Tour’s lab and current postdoctoral researcher at Tianjin.

“We should also be able to use this process to produce specific types of graphene foam like 3D printed rebar graphene as well as both nitrogen- and sulfur-doped graphene foam by changing the precursor powders.”

To create their blocks of graphene, the researchers used a CO2 laser—the kind used by laser sintering 3D printers. When the laser was shone onto the sugar and nickel powder, the sugar was melted and the nickel acted as a catalyst. A low-density graphene with large pores then formed as the mixture cooled down. (These pores accounted for 99 percent of the material’s volume.)

This laser shining process was repeated over and over again with different parameters, as the researchers sought to find the optimal amount of time and laser power that would maximize graphene production.

James Tour, the T.T. and W.F. Chao Chair in Chemistry at Rice University

Having settled on an effective combination of parameters, the researchers believe that their technique could have many uses across different fields.

“The 3D graphene foams prepared by our method show promise for applications that require rapid prototyping and manufacturing of 3D carbon materials, including energy storage, damping, and sound absorption,” said co-lead author Yilun Li, a graduate student at Rice.

http://www.3ders.org/articles/20170621-laser-3d-printing-helps-rice-tianjin-researchers-create-atomically-thin-graphene.html



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