First principles energetic calculations of sapphire (0001) and (1(bar 1)02) surfaces

摘要

Various crystallographic faces of sapphire, the undoped single crystal (alpha)-Al(sub 2)O(sub 3), have been widely used as substrates for depositing thin films of metals, semiconductors, and insulators for basic scientific studies and for microelectronic applications. Epitaxial TiO(sub 2) and VO(sub 2) thin films were successfully grown on (0001), (1102) and (1120) surfaces of sapphire substrates by the Metal Organic Chemical Vapor Deposition (MOCVD) technique in our experimental program. The present paper is one of our theoretical efforts in parallel with the experimental program to gain microscopic understandings of the effects of substrate structure on the epitaxial relationship and the overlayer lattice structure of thin film deposition. The first principles energetic calculations on the complicated surfaces like sapphire can now be carried out because of the recent development in our computer programs and availability of high speed super computers. The phase first principles means that the calculations are based only on the known physical laws and approximations, and are free of any adjustable parameters. A complete discussion of the theoretical formalism has been presented in our previous works.