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

Infrared absorption from oxygen-related defects in Si crystals irradiated w ith electrons (2.5 MeV) at room temperature (RT) and in the range 300-600 d egrees C has been investigated. Two new vibrational bands positioned at 10 K at about 1370 and 1430 cm(-1) were observed in samples irradiated at RT. A good correlation is found between these lines and the bands at 836 and 88 5 cm(-1) known to originate from asymmetrical stretching vibrations (B-1 mo de) of an oxygen atom in the neutral and negative VO complex. An attributio n of the 1370 and 1430 cm(-1) bands to a combination of the B-1 mode with t he symmetrical stretching A(1) mode (weakly IR active) for different charge states of VO is argued to be the most probable. A band at 833.4 cm(-1) is found to increase in strength upon annihilation of divacancies at 250-300 d egrees C. The V2O complex is suggested to give rise to this band. New exper imental data confirming an attribution of the 895 cm(-1) band to the VO2 co mplex are presented as well. (C) 1999 Elsevier Science B.V. All rights rese rved.