Cu0*: A metastable configuration of the{Cus,Cui}pair in Si

Abstract

First-principles theory shows that the substitutional-interstitial copper pair in Si (Si-${\mathrm{Cu}}_{s}\ensuremath{\cdots}{\mathrm{Cu}}_{i}$) has a metastable state with ${\mathrm{Cu}}_{i}$ very near a tetrahedral interstitial site in a trigonal ${\mathrm{Cu}}_{s}\text{\ensuremath{-}}\mathrm{Si}\ensuremath{\cdots}{\mathrm{Cu}}_{i}$ configuration that exhibits three low-frequency pseudolocal vibrational modes. The lowest of them, at $40\phantom{\rule{0.3em}{0ex}}{\mathrm{cm}}^{\ensuremath{-}1}$, has ${A}_{1}$ symmetry and is the likely source of the phonon sidebands observed at $52\phantom{\rule{0.3em}{0ex}}{\mathrm{cm}}^{\ensuremath{-}1}$ in the photoluminescence band of a defect known as $^{*}\mathrm{Cu}_{0}$.