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

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Journal Article
Carbon, 2015, 91 pp. 378 - 385
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© 2015 Elsevier Ltd. All rights reserved. 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 (1 1 1)/Si (1 1 1) samples in Ultra High Vacuum. By using STM we were able to observe very clear atomic resolution images of the transition from SiC (√3×√3)R30°to a new intermediate stage SiC (3/2×√3)R30°(very close to the graphene (2 × 2) reconstruction) after annealing at 1250°C. We also obtained images of the transformation of the intermediate structure into a (1 × 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 (√3×√3)R30°reconstruction, but fail to describe the SiC (3/2×√3)R30°structure due to its incommensurability with the 3C-SiC (1 1 1) lattice.
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