Tuesday, December 18, 2012

1212.3993 (F. Forster et al.)

Confocal Raman spectroscopy of graphene on hexagonal boron nitride    [PDF]

F. Forster, A. Molina-Sanchez, S. Engels, A. Epping, K. Watanabe, T. Taniguchi, L. Wirtz, C. Stampfer
We investigate the influence of the substrate on the vibrational properties of graphene, comparing graphene on hexagonal boron nitride (hBN) with graphene on SiO2 by spatially resolved confocal Raman spectroscopy. By studying the G-line we show that the average doping level and local doping domain fluctuations are significantly suppressed in graphene on hBN with respect to graphene on SiO2. However, in contrast to the G-line, the 2D-line of graphene on hBN shifts up in frequency compared to the one of graphene on SiO2. We show that this effect is due to a reduction of the Kohn anomaly at K through an enhanced screening by the dielectric substrate. We prove our theory to be consistent with Raman measurements on graphene surrounded by hBN (stronger screening) and recent findings on suspended graphene (no external screening).
View original: http://arxiv.org/abs/1212.3993

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