Large Variations of the Raman Signal in the Spectra of Twisted Bilayer Graphene on a BN Substrate

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• 作者：Martin Kalbac ; Otakar Frank ; Jing Kong ; Javier Sanchez-Yamagishi ; Kenji Watanabe ; Takashi Taniguchi ; Pablo Jarillo-Herrero ; Mildred S. Dresselhaus
• 刊名：The Journal of Physical Chemistry Letters
• 出版年：2012
• 出版时间：March 15, 2012
• 年：2012
• 卷：3
• 期：6
• 页码：796-799
• 全文大小：221K
• 年卷期：v.3,no.6(March 15, 2012)
• ISSN：1948-7185

文摘

We report an unusual enhancement of the Raman signal of the G mode in a twisted graphene bilayer (2-LG) on a hexagonal single-crystalline boron nitride substrate. We used an isotopically engineered 2-LG, where the top layer was composed of ¹³C atoms and the bottom layer of ¹²C atoms. Consequently, it was possible by Raman spectroscopy to distinguish between the enhancement coming from the top and bottom layers. The enhancement of the G mode was, however, found to be similar for the top and bottom layers, and this enhancement effect was observed only at certain locations on the substrate. The experiment with two different laser excitation energies showed that the location of the enhanced spots is dependent on the laser excitation energy. Therefore our results suggest that the enhancement comes from new states in the electronic structure, which are a consequence of a local specific rotation of the grains in graphene layers.

Keywords:

graphene; bilayer; Raman spectroscopy