The transition from 3C SiC (1 1 1) to graphene captured by Ultra High Vacuum Scanning Tunneling Microscopy

In this paper we clarify the transformation mechanism of 3C-SiC into graphene upon thermal decomposition, by a combination of high resolution Scanning Tunneling Microscopy (STM) images and first principle calculations. We studied the transition from 3C-SiC to graphene by high temperature annealing of C-terminated 3C SiC (111)/Si (111) samples in Ultra High Vacuum. By using STM we were able to observe very clear atomic resolution images of the transition from SiC (root 3 x root 3)R30 degrees to a new intermediate stage SiC (3/2 x root 3)R30 degrees (very close to the graphene (2 x 2) reconstruction) after annealing at 1250 degrees C. We also obtained images of the transformation of the intermediate structure into a (1 x 1) monolayer graphene, caused by further sublimation of atoms in the subsurface layer. We have interpreted the results by using Density Functional Theory - Local Density Approximation calculations, which give full account of the SiC (root 3 x root 3)R30 degrees reconstruction, but fail to describe the SIC (3/2 x root 3)R30 degrees structure due to its incommensurability with the 3C-SiC(111) lattice. (C) 2015 Elsevier Ltd. All rights reserved.