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Indexed by:期刊论文

Date of Publication:2007-11-01

Journal:SURFACE SCIENCE

Included Journals:SCIE、EI、Scopus

Volume:601

Issue:21

Page Number:5050-5056

ISSN No.:0039-6028

Key Words:computer simulations; surface relaxation and reconstruction; surface electronic phenomena; aluminum oxide; chromium oxide

Abstract:Ab initio total energy Hartree-Fock calculations of ultrathin films of alpha-Al2O3 on (0001) alpha-Cr2O3 templates are presented. The surface relaxation, the in-plane reconstruction and the surface and strain energies of the slabs are studied as a function of alumina film thickness. The surface Al layer is found to relax inwards considerably, with the magnitude of the inwards relaxation depending on the thickness of the ultrathin alumina film in a non-linear manner. The calculations also reveal that ultrathin films of alumina lower the surface energy of (0001) alpha-chromia substrates. This indicates that the (0001) alpha-chromia surface provides favourable conditions for the templated growth of a-alumina. However, increasing the alumina film thickness is found to give rise to a significant. increase in strain energy. Finally, the electronic properties at the surface of the (0001) alpha-Al2O3/alpha-Cr2O3 slabs are investigated. Here it is found that the alumina coating gives rise to an increase in the covalency of the bonds at the surface of the slabs. In contrast, the influence of an alumina layer on the electrostatic potential at the surface of the chromia slab is relatively minor, which should also be beneficial for the templated growth of aalumina on (0001) alpha-chromia substrates. (C) 2007 Elsevier B.V. All rights reserved.