PORTLAND, Ore.—Preparing the way for carbon-based semiconductors, Texas Instruments Inc. is perfecting the growth of graphene sheets. By carefully characterizing a method of growing graphene monolayers, TI hopes to pave the way for faster, smaller and lower power electronics based on carbon instead of silicon.
"This research is teaching us a lot on fundamental mechanisms of graphene growth," said TI Fellow Luigi Colombo. "We believe that the results of this work will lead scientists and engineers to further increase the size of the single crystal graphene and also improve the electrical characteristics of the material."
TI recently demonstrated growing large-grain graphene crystals—up to half a millimeter in diameter—in collaboration with IBM's T.J. Watson Research Center, the Nanoelectronic Research Initiative (NRI), and the University of Texas. Using low-pressure chemical vapor deposition inside copper-foil enclosures, with methane as a precursor, the resulting graphene films were then transferred to doped single-crystal silicon and silicon-on-insulator substrates where their electrical characteristics were tested. The team is also pursuing ways of growing graphene directly on dielectric substrates.
"Growth on other substrates, preferably dielectrics or metals more stable than copper, are also being investigated," said Colombo.
Large-grain crystals of graphene start as perfect hexagons but grow more quickly at their tips (rather than the sides of the hexagon) resulting in snowflake-like fractal islands.
For several years now, TI has been quietly pursuing graphene growth methods, previously reporting surface nucleation followed by a two-dimensional growth process on copper substrates with CVD. However, the domains were only 10-to-20 microns, 30 times smaller than the half-millimeter (500 micron) domains on which TI is now reporting.
Using low-energy electron microscopy the research team was able to confirm that the films were relatively uniform single-crystal graphene monolayers. Using Raman spectroscopy, the researchers were able to confirm an electron mobility of 4000 square centimeters per volt second--compared to 1,400 cm2/Vs for silicon and 8500 cm2/Vs for gallium arsenide. Theoretically, graphene can achieve electron mobilities of 10,000-to-100,000 cm2/Vs.
"4000 [cm2/Vs] is reasonably high, but not as high as the highest value possible for exfoliated films, so we still have some improvements to make in our process," said Colombo. "But we have high hopes for these large-domain films."
The large-domain graphene growth was promoted inside the copper-foil cage at a relatively high temperature—over 1,035 degrees Celsius (1,895 Fahrenheit). After processing the films, field-effect transistors were fabricated by transferring the films to highly doped silicon substrates, which served as the back-gate contact, with source and drain electrodes made from nickel. Electron mobility was inferred from measuring resistance was as a function of back-gate voltage.
Funding was provided by the National Science Foundation, the Office of Naval Research and Semiconductor Research Corp.'s NRI at the SouthWest Academy of Nanoelectronics.
by far the most interesting though is apparently this latest practical tool to finally measure and even effect Andreev bound states (ABS)?
"If you have two superconductors with a normal metal between, you can actually transport the superconductivity across the normal material via these bound states, even though the normal material doesn't have the electron pairing that the superconductors do," Mason said.
ABS are extremely difficult to measure or to observe directly. Researchers can measure conduction and overall magnitude of a current, but have not been able to study individual ABS to understand the fundamental physics contributing to these unique states.
Mason's group developed a method of isolating individual ABS by connecting superconducting probes to tiny, nanoscale flakes of graphene called quantum dots. ..."
so assuming their superconducting probes where not this superconducting graphene but standard graphene then cant they also take even more advantage of the higher temperature inside your average silicon and make use of that heat to induce some super conductivity property in a hybrid core today...
or did i misunderstand the concepts due the scientific ether/or thinking in these links? why cant we have both states and make use of them interacting.
we probably need a layman's guide on all this and what it mean's.
but it seems there was lot's of talk about Superconductivity at 'room temperature' with graphene and using that in CPU design etc...
stating room temperature CPU's always struck me as an odd goal as silicon CPU's have always run hotter inside, even if they only get warm by the time that generated heat reaches the outside packaging/lid
however there are high-temperature uperconductors and talk of making Graphene: A Superconductor
We just want to clarify that the graphene growth referred to in this article was all performed in Prof. Rod Ruoff’s laboratory at UT Austin, in which we have been working with his group over the past 4 years in developing the process.
Furthermore, the precise nature of the collaboration with IBM on this work was on the verification that the graphene grown at UT Austin by this method was indeed single crystal as described in our recently accepted joint article currently online on the Journal of the American Chemical Society website.
I agree Colin, sounds they will be able to grow graphene monolayers across the whole wafer one day but material science always takes much longer than people believe...I would give 10 years until graphene is commercially available...and it will help achieve Kurzweil's singularity ;-)...Kris
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