Identification of the oxygen-vacancy defect containing a single hydrogen atom in crystalline silicon

Float-zone and Czochralski-grown silicon crystals have been implanted with protons or deuterons at similar to 50 K. Electron paramagnetic resonance me asurements reveal a new signal in the spectrum of the Czochralski-grown (ox ygen-rich) material. This signal is strongly temperature dependent, display ing a transition from monoclinic-I to orthorhombic-I symmetry in the temper ature ranges 180-240 K and 230-290 K in the proton-and deuteron-implanted s amples, respectively. The g tensor observed at low temperature as well as a large Si-29 hyperfine splitting associated with a unique silicon site are typical of a vacancy-type defect with the unpaired electron confined to a d angling-bond orbital. Proton hyperfine splittings show that a single hydrog en atom is incorporated in the defect and strongly suggest that the defect contains only one vacancy. The observations allow an unequivocal assignment of the signal to VOH0, the neutral charge state of the monovacancy-oxygen defect (the A center) containing a single hydrogen atom. It is found that t he hydrogen atom may jump rather easily between the two equivalent sites ly ing in the (110) mirror plane of the defect.