Defects at the Si(001)/a−SiO2 interface: Analysis of structures generated with classical force fields and density functional theory

Abstract

Defects at the $\text{Si}(001)/a\text{\ensuremath{-}}{\mathrm{SiO}}_{2}$ interface were simulated using a combination of classical force field molecular dynamics and first-principles total-energy minimization techniques. The second generation charge-optimized many-body potential COMB10 was used to generate $a\text{\ensuremath{-}}{\mathrm{SiO}}_{2}$ which was placed on an ideally terminated Si(001) surface and briefly annealed before being relaxed using density functional theory. Si dimers form at the Si interface on relaxation unless the Si surface has been oxidized. ${P}_{b1}$ defects form when Si dimers do not bond to O atoms in the $a\text{\ensuremath{-}}{\mathrm{SiO}}_{2}$ layer. Mismatch in Si atom pairings at the dimerized surface leads to ${\mathrm{Si}}_{2}\mathrm{O}\ensuremath{\equiv}\mathrm{Si}\ifmmode\cdot\else\textperiodcentered\fi{}$ defects at the interface which may be the structure of a defect denoted $S$ in electron-spin resonance (ESR) studies. Relatively few ${P}_{b0}$ defects with a magnetic moment form at the Si interface. $a\text{\ensuremath{-}}{\mathrm{SiO}}_{2}$ generated by heating and quenching a system with periodic boundary conditions is free of ${E}^{\ensuremath{'}}$ defects. Afterward, this structure is placed on the Si surface and allowed to relax. The main type of ${E}^{\ensuremath{'}}$ defect which forms is a forward oriented ${E}_{\ensuremath{\alpha}}^{\ensuremath{'}}$ defect. ESR hyperfine parameters for each defect category are calculated and compared to experimental data. Defect densities of states are calculated and compared to experiment.