From: David Vanderbilt <dhv@pion.rutgers.edu> Date: Fri, 6 Nov 1998 19:04:06 GMT (96kb)
Authors:
Kwok-On Ng,
David Vanderbilt (Department of Physics and Astronomy, Rutgers University)
Comments: 7 pages, two-column style with 6 postscript figures embedded. Uses
REVTEX and epsf macros. Also available at
this http URL
Subj-class: Materials Science
We present first-principles calculations of the structural and electronic properties of Si(001)-SiO2 interfaces. We first arrive at reasonable structures for the c-Si/a-SiO2 interface via a Monte-Carlo simulated annealing applied to an empirical interatomic potential, and then relax these structures using first-principles calculations within the framework of density-functional theory. We find a transition region at the interface, having a thickness on the order of 20\AA, in which there is some oxygen deficiency and a corresponding presence of sub-oxide Si species (mostly Si^+2 and Si^+3). Distributions of bond lengths and bond angles, and the nature of the electronic states at the interface, are investigated and discussed. The behavior of atomic oxygen in a-SiO2 is also investigated. The peroxyl linkage configuration is found to be lower in energy than interstitial or threefold configurations. Based on these results, we suggest a possible mechanism for oxygen diffusion in a-SiO2 that may be relevant to the oxidation process.