Observation and theory of theV−O−H2complex in silicon

Abstract

The interaction of hydrogen with radiation-induced defects (RD's) in Czochralski-grown silicon crystals has been studied by infrared-absorption spectroscopy and ab initio modeling. Hydrogen and/or deuterium was introduced into the crystals by indiffusion from ${\mathrm{H}}_{2}$ $({\mathrm{D}}_{2})$ gas at $1200--1300\ifmmode^\circ\else\textdegree\fi{}\mathrm{C}.$ The samples were subsequently irradiated with fast electrons $(E=2\ensuremath{-}4 \mathrm{MeV})$ and annealed in the temperature range of $100--600\ifmmode^\circ\else\textdegree\fi{}\mathrm{C}.$ The centers produced by the irradiation were the same in both the untreated and treated cases, namely the A-center, ${\mathrm{C}}_{i}\ensuremath{-}{\mathrm{O}}_{i}$ complex, and divacancy. A heat treatment of the H-treated samples resulted in the enhanced loss of these centers and the formation of centers containing hydrogen. The disappearance of the A centers in the temperature range of $100--150\ifmmode^\circ\else\textdegree\fi{}\mathrm{C}$ is correlated with the appearance of three local vibrational modes (LVM's) at 943.5, 2126.4, and $2151.5 {\mathrm{cm}}^{\ensuremath{-}1}.$ The isotopic shifts of these lines were obtained from measurements on the samples doped with hydrogen and deuterium. The lines are identified as related to stretching vibrational modes of a complex that consists of one oxygen and two hydrogen atoms sharing a vacancy site $(V\ensuremath{-}\mathrm{O}\ensuremath{-}{\mathrm{H}}_{2}$ complex). Ab initio calculations are used to explore the structures and properties of this defect. The origin of other LVM bands, which were observed upon annealing, is discussed.