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| Institute of Semiconductors physical properties of multilayer graphene made new progress |
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Graphene is a single layer of carbon atoms tightly packed into a two-dimensional carbon honeycomb lattice structure of new materials. Because of its unique structure and excellent dimensional crystallographic quality graphene contains a rich and novel physical phenomena, it quickly became one of the hot areas of condensed matter physics in recent years. Graphene can drill in different ways multilayer graphene stacks, each multi-layered graphene materials exhibit unique electronic band structure. Information excited probe the electronic band structure of graphene There are many methods. However, due to technical reasons or resolution, the detection limits of these technologies is difficult as small low-energy electrons near the Dirac point 100meV excitation information. Therefore, how to study multi-band structure of graphene near the Dirac information has been people want to solve the problem.
Raman mode interaction between the electron excitation is by measuring the low-frequency Raman signals to detect the corresponding low-energy electronic excitations provides a very effective way. Low-frequency Raman modes typically use three grating Raman spectroscopy to measure, but the very low optical transmittance as it is difficult to be used to study multi-graphene and graphite has a very weak intensity such low-frequency Raman mode.
Bragg grating technology integrated into the body of a single grating Raman spectrometer major scientific research projects in support of the Ministry of Science and the National Natural Science Foundation, the National Laboratory of the semiconductor superlattice semiconductor researcher Tan Pingheng the latest developments in the research group, so that it can measured as low as 5cm-1 Stokes and anti-Stokes Raman signal. Single grating spectrometer very high so that the transmittance of the optical signal can be detected from the discussion group graphene layer, the multi-graphene graphite extremely weak intensity of the low-frequency shear modulus, shear modulus from the position of the peak of graphite 43cm-1 to bilayer graphene becomes 31cm-1.Due to the shear modulus of graphene frequency is very low, only 5 mev phonon energy, is far less than the graphene G 0.2 eV mode phonon energy, therefore, shear modulus and graphene Dirac point near the low energy electron excitation occur significant interaction, making multilayer graphene showed Fano linear shear modulus.But as the number of graphene layers is less, because of the adsorption air molecules and as a result of the charge transfer between substrate and doping effect is significant, making the Fano resonance coupling effect is more and more weak, so that the double-layer graphene linear close lorentz linear shear modulus.
The above results of theoretical work to get there by the semiconductor, a researcher at nankai university professor Wang Yufang, Britain of Marzari at Oxford and Cambridge university professor Ferrari team closely. Relevant results have been published in Nature Materials 4, 294-300 (2012). Professor Tan Pingheng researcher and Ferrari to be a common corresponding author of this paper.
Graphite is not the only layer material, BN, Bi2Te3 and Bi2Se3 layered materials can be preparation by mechanical and physical stripping or chemical methods. All of these material shear modulus test would be used to directly detect their interaction between the layers and push related research of physical propertie.. | | |  |
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