Core-Level Shift of Graphene with Number of Layers Studied by Microphotoelectron Spectroscopy and Electrostatic Force Microscopy

Abstract

The dependence of C-1s core-level shift (CLS) of graphene on the number of layer (NL) is significant information to derive the coordination-resolved C1s core-level energy (E-1s) of carbon allotropes. To observe the variation of CLS of graphene with NL, binding energy and work function of graphene with various NL were examined by scanning photoelectron microscopy/spectroscopy and electrostatic force microscopy. E1s of grounded graphene decreased as NL increased. The E-1s of single-layer graphene and multilayer graphene (MLG) is 289.42 and 289.13 eV, respectively. Based on the NL-dependent E1s of graphene, the CLS of C-1s between a free carbon atom and diamond is 0.74 eV, calculated by the bond-order-length-strength correlation theory. The CLS of graphene with NL supported the existence of surface core-level shift (SCLS) on graphite. The magnitude of SCLS in MLG was +0.09 eV. The effective coordination number is 3.68 for bilayer graphene and 4.31 for the surface carbon layer in MLG.