Search

We present full ab initial calculations of both molecular and atomic oxygen reacting with hydrogen passivated Si(100) 2 × 1 reconstructed surface. The calculations are based on the density functional theory via a pseudopotential method. Preliminary results reported concern the search for the oxygen preferential setting on the surface. For molecular oxygen only physisorbed states are found. For atomic oxygen, oxidation reaction occurs and we find two preferential sites for the oxygen. In the first case we show how Si H bonds on the hydrogenated surface dimers are broken. The second case is a direct barrierless and destructive subsurface oxidation.

We have simulated the growth of GaSb/(00l)GaAs, and we have focused our study on the defects creation at the DA and DB double steps on the substrate. A Monte Carlo scheme associated with a valence force field approximation is used to describe, respectively, the kinetic and the strain effects in the mis-matched film. These simulations indicate a strong localization of dislocation half loops at the step edges in accordance with experimental observations.

Simulation of heteroepitaxial growth with high lattice mismatch is reported. The dynamics of layer growth is treated using the Monte Carlo technique and the energetics aspects related to the effect of strain are accounted for in the VFF approximation. It is shown that the surface becomes rough and 3D islands, showing (111) facets, appear. The strain relaxation is shown to be almost complete after a few atomic layers. Formation of point and extended defects is observed in the deposited layers.

We have performed an atomic-scale simulation of lattice-mismatched heteroepitaxial growth of semiconductors with a zincblende structure by associating the Monte Carlo technique with an energy model based on the valence force field approximation. We have observed the formation of misfit dislocations by alignment of point defects. We have evaluated the critical thickness for their creation which are in good agreement with experimental results for high lattice mismatches (greater than 6%), while previous macroscopic models give good results for low lattice mismatches (less than 4%). The deposition of alloy films is investigated to study the variations in the density and the nature of interface defects, leading to misfit dislocations.