Local vibrational modes of weakly bound O-H complexes in Si

Local vibrational modes of two oxygen-hydrogen complexes have been identified with infrared absorption spectroscopy. Samples of intrinsic silicon and samples doped with O-16 or O-18 isotopes were implanted with protons and deuterons at similar to 20 K. After the implantation, infrared absorbance spectra were measured at 8 K on unannealed samples. An oxygen mode at 1077 cm(-1) and a hydrogen mode at 1879 cm(-1), which originate from the same defect OHI were observed in the as-implanted samples. Heat-treatment at 200 K produced a new center OHII with modes at 1028 and 1830 cm(-1). OHI anneals out at similar to 130 K while OHII is stable up to similar to 240 K. OHI and OHII are tentatively identified with two complexes of interstitial oxygen and bond-centred hydrogen. Ab initio theory was applied to calculate the structure and local modes of three such complexes. The results qualitatively support our tentative assignments.