Joachim Dahl Thomsen and Tim J. Booth Department of Micro and Nanotechnology, Technical University of Denmark  Graphene is known to show corrugations on the nanometer scale, often referred to as intrinsic ripples [1, 2], which may limit the electron mobility and conductivity [3]. In this study we measured the intrinsic roughness of various suspended graphene samples (exfoliated and grown by chemical vapor deposition), using electron diffraction patterns in a transmission electron microscope. We measure graphene samples as well as graphene on hexagonal boron nitride (hBN), suspended over round and rectangular apertures. For suspended graphene, we show a tendency of the ripples to be oriented along the rectangular apertures, while the same trend is not seen for round apertures. For graphene on hBN, we show a strong suppression in the roughness of graphene; possibly reducing the roughness to zero within our measurement limits.[1] – “The structure of suspended graphene sheets”, J. C. Meyer et. al, Nature 446, pp. 60-63 (2007) [2] – “Measuring the corrugation amplitude of suspended and supported graphene”, D. A. Kirilenko et. al, PRB 84, 235417 (2007) [3] – “Electron scattering on microscopic corrugations in graphene”, M. I. Katsnelson and A. K. Geim, Phil. Trans. R. Soc. 366, pp. 195-204 (2008)  Joachim Dahl Thomsen is currently a Ph.D. student at the Technical University of Denmark (DTU). He is working primarily with in-situ transmission electron microscopy (TEM) experiments involving nanopatterning and characterisation of graphene and other 2D materials, using microfabricated platforms compatible with TEM sample holders. Joachim received his M.Sc. degree in Physics and Nanotechnology from DTU in 2014 where he worked with cleanroom micro-fabrication of flexible arrays of photodetectors in his final project. |
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