Peking University, China
Lun Dai has completed her PhD at the age of 33 years in Physics from PekingUniversity at Beijing, China in 1999. She is now Professor in School Physics, Peking University. Her research career has focusedprimarily on nano-semiconductor material, nano-electronic and nano-photonic device physics. She has published more80 SCI papers in reputed journals, including Nature, Nano Lett., Adv. Mater., JACS, ACS nano, J. Mater. Chem., Appl. Phys. Lett. etc. Total citation times for these papers are more than 1000.
We have grown large-scalehigh-qualigymonolayer and bilayer graphenes with chemical vapor deposition(CVD)method, transferred them on SiO2/Si substrates,and studied their Raman spectrumevolution with thethickness of the SiO2 capping layer experimentally and theoretically. We found that for both monolayer and bilayer graphenes, the intensities of D, G, 2D bands (ID, IG, I2D) and the intensity ratio of 2D band to G band (I2D/IG) oscillate as SiO2 thickness increasing. Besides,their oscillation amplitudes vary with SiO2 thickness.Theoretically, we used the Fresnel’s equations based multireflection model (MRM) to simulate the effect ofSiO2thickness on IDG, I2D, and I2D/IG. The result coincides with the experimental result. Besides, the simulated result in a wide range of SiO2thickness shows that the oscillation amplitudes of all the band intensities present kind of beat feature. We also studied the effect of incident light wavelength on ID, IG, I2D, and I2D/IG. Our work has practical meaning in using the Raman footprintsto identify the layer number of graphene on SiO2/Si substrate.
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