Defect-induced dissociation of H2 in silicon

摘要: Ab initio molecular-dynamics simulations of intrinsic defects and hydrogen in crystalline silicon reveal an unexpected process with considerable implications. The vacancy $(V)$ the self-interstitial $(I),$ both rapid diffusers $c\ensuremath{-}\mathrm{Si},$ dissociate interstitial ${\mathrm{H}}_{2}$ molecules a substantial gain energy: $V+{\mathrm{H}}_{2}\ensuremath{\rightarrow}{V,\mathrm{H},\mathrm{H}}+4.0\mathrm{eV}$ $I+{\mathrm{H}}_{2}\ensuremath{\rightarrow}{I,\mathrm{H},\mathrm{H}}+1.7\mathrm{eV}.$ dissociation is caused by lattice strain associated defect, occurs whenever are vicinity strained Si-Si bonds. After dissociation, two H's may either bind to defect that or diffuse away from it. calculated Frenkel pair formation energy 8.2 eV. reaction ${\mathrm{H}}_{2}{+\mathrm{H}}_{2}\ensuremath{\rightarrow}{V,{\mathrm{H}}_{4}}+I$ releases less than 0.1 eV, suggesting ${\mathrm{H}}_{2}$'s otherwise perfect Si will not generate defects.