Observation and theory of the V-O-H₂ complex in silicon

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 H₂ (D₂) gas at 1200–1300°C. The samples were subsequently irradiated with fast electrons (E=2-4 MeV) and annealed in the temperature range of 100–600°C. The centers produced by the irradiation were the same in both the untreated and treated cases, namely the A-center, C_i-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°C is correlated with the appearance of three local vibrational modes (LVM’s) at 943.5, 2126.4, and 2151.5 cm^-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-O-H₂ 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.