Vibrational absorption from vacancy-oxygen-related complexes (VO, V2O, VO2) in irradiated silicon

Infrared absorption from oxygen-related defects in Si crystals irradiated with electrons (2.5MeV) at room temperature (RT) and in the range 300–600°C has been investigated. Two new vibrational bands positioned at 10K at about 1370 and 1430cm−1 were observed in samples irradiated at RT. A good correlation is found between these lines and the bands at 836 and 885cm−1 known to originate from asymmetrical stretching vibrations (B1 mode) of an oxygen atom in the neutral and negative VO complex. An attribution of the 1370 and 1430cm−1 bands to a combination of the B1 mode with the symmetrical stretching A1 mode (weakly IR active) for different charge states of VO is argued to be the most probable. A band at 833.4cm−1 is found to increase in strength upon annihilation of divacancies at 250–300°C. The V2O complex is suggested to give rise to this band. New experimental data confirming an attribution of the 895cm−1 band to the VO2 complex are presented as well.