Is silicon dioxide essential to make graphene visible? Case studies of graphene-substrate interactions
許紘瑋1, 張羅嶽1,2, 陳虹穎2, 陳至瑋3, 吳忠霖3, 果尚志1,2, 陳家浩1*
1National Synchrotron Radiation Research Center, Hsinchu, Taiwan
2Department of Physics, National Tsing Hua University, Hsinchu, Taiwan
3Department of Physics, National Cheng Kung University, Tainan, Taiwan
* presenting author:陳家浩,
Making the mechanically exfoliated graphene flakes visible is the key to successfully study the intrinsic properties of graphene-substrate interactions. Conventionally, this can only be achieved by placing the graphene flakes on top of silicon substrate with 300 nm SiO2 overlayer, but this severely limited our investigation regarding graphene-substrate interactions. We therefore started to ask ourselves, is silicon dioxide the only material to make graphene visible? Moreover, a recent study has successfully demonstrated a working GaN-based LED with CVD-synthesized multi-layer graphene as conduction electrodes. However, the energy coupling between graphene and GaN is still unclear. To fully utilize the advantages of graphene to improve our daily life, a further understanding of the electronic structure between graphene and the substrate is an urgent task. To answer those questions, we employed theoretical simulation using a model based on Fresnel’s law, to calculate the optical contrast of single-layer graphene on various substrate structures. Based on the results, we grew those particular substrates to test the graphene visibility. The graphene flakes and thickness were verified by optical microscope and micro-Raman spectroscopy. The graphene-substrate interactions were then studied by scanning photoelectron microscopy. Based on our results, the graphene on two different types of substrates were studied and will be presented.

Keywords: graphene, scanning photoelectron microscopy, graphene-substrate interaction