Jiang-Bin Wu1, Zhi-Xin Hu2, Xin Zhang1, Wen-Peng Han1, Yan Lu1, Wei Shi1, Xiao-Fen Qiao1, Mari Ijias3, Silvia Milana3, Wei Ji2, Andrea C. Ferrari3, and Ping-Heng Tan1
1State Key Laboratory of Superlattices and Microstructures, Institute of Semiconductors, Chinese Academy of Sciences, Beijing 100083, China
2Department of Physics, Renmin University of China, Beijing 100872, China
3Cambridge Graphene Centre, University of Cambridge,Cambridge CB3 0FA, UK
Email: email@example.com (W.J.), firstname.lastname@example.org (P.H.T.)
DOI:10.1021/acsnano.5b02502 Publication Date: June 6th, 2015
Raman spectroscopy is the prime non-destructive characterization tool for graphene and related layered materials. The shear (C) and layer breathing modes (LBMs) are due to relative motions of the planes, either perpendicular or parallel to their normal. This allows one to directly probe the interlayer interactions in multilayer samples. Graphene and other two-dimensional (2d) crystals can be combined to form various hybrids and heterostructures, creating materials on demand with properties determined by the interlayer interaction. This is the case even for a single material, where multilayer stacks with different relative orientation have different optical and electronic properties. In twisted multilayer graphene samples there is a significant enhancement of the C modes due to resonance with new optically allowed electronic transitions, determined by the relative orientation of the layers. Here we show that this applies also to the LBMs, that can be now directly measured at room temperature. We find that twisting does not affect LBMs, quite different from the case of the C modes. This implies that the periodicity mismatch between two twisted layers mostly affects shear interactions. Our work shows that Raman spectroscopy is an ideal tool to uncover the interface coupling of 2d hybrids and heterostructures.