Localized modes and divacancy absorption in oxygen-ion-implanted Si

Optical absorption bands characteristic of localized vibrational modes for both interstitial and substitutional oxygen have been observed in crystalline Si implanted with 220-keV oxygen ions at 300°K. In addition, the fluence dependences for the vibrational modes and also for an electronic transition of the divacancy (1.8-μ band) have been measured. Implanted oxygen ions are found to enhance divacancy formation. This effect was not observed for Sb implantation. The sum of the observed interstitial and substitutional oxygen centers is approximately equal to the number of implanted oxygen ions. An ion fluence 300 times larger than that to detect divacancies was required to detect the vibrational modes of oxygen as expected from the relative production rates and absorption coefficients. At these high fluences the strengths of the vibrational bands increase in magnitude with fluence while the divacancy band decreases. At even higher fluences amorphous layer formation, as indicated by a milky coloration of the surface, caused a decrease in the spacing of optical interference fringes and in the magnitude of the oxygen vibrational bands.