Interface Oxidative Structural Transitions in Graphene Growth on SiC (0001)

• Published in: Journal of physical chemistry. C 2012-07, Vol.116 (29), p.15342-15347
• Main Authors: Lu, Weijie, Barbosa, Roland, Clarke, Edwina, Eyink, Kurt, Grazulis, Lawrence, Mitchel, William C, Boeckl, John J
• Format: Article
• Language: English
• Subjects: Composition and phase identification; Condensed matter: electronic structure, electrical, magnetic, and optical properties; Condensed matter: structure, mechanical and thermal properties; Cross-disciplinary physics: materials science; rheology; Electronic structure and electrical properties of surfaces, interfaces, thin films and low-dimensional structures; Exact sciences and technology; Fullerenes and related materials; diamonds, graphite; Materials science; Methods of deposition of films and coatings; film growth and epitaxy; Physics; Specific materials; Surface and interface electron states; Surface states, band structure, electron density of states; Surfaces and interfaces; thin films and whiskers (structure and nonelectronic properties); Theory and models of film growth; Thin film structure and morphology
• ISSN: 1932-7447; 1932-7455
• DOI: 10.1021/jp301996h

The structural transition from a three-dimensional SiC lattice to a two-dimensional graphene sheet is a crucial element in the growth mechanism of graphene on SiC. An interfacial defective transition layer near the surface of the SiC substrate is believed to be an intermediate structure for graphene layer formation. The transition layer consists of SiO x C y , vacancies, and other defects in the SiC lattice, which result from Si evaporation via thermal degradation of the SiC lattice and oxidation reactions of residual oxygen and other oxygen containing molecules on the SiC surface at high temperatures. This partially oxidized and structurally degraded SiC lattice layer is formed at temperatures lower than the graphene growth temperature but then decomposes with increasing temperature, leading to graphene formation. Then, the growth mechanism for graphene on SiC (0001) in high vacuum consists of multiple steps, including Si removal by thermal decomposition and oxidation, collapsing of the near surface SiC lattice, conversion from sp3 to sp2 carbon, and an increase in the degree of low-dimensional graphitization. The proposed atomic scale mechanism is able to explain experimental phenomena in graphene/SiC structural growth, such as graphene coverage at step edges, growth environment effects, graphene domain size, and thickness variations.