POSITION ANNIHILATION IN SIO2 SI STRUCTURE AT LOW-TEMPERATURE/

Annihilation characteristics of positrons in SiO2/Si structure were st udied by using a monoenergetic positron beam in the temperature range between 50 K and room temperature. In the SiO2 film, positrons formed positronium (Ps) and they annihilated from localized states in open sp aces. Below 100 K, the Ps formation was found to be suppressed. This f act was attributed to the trapping of positrons by point defects in th e SiO2 film at low temperature. The depth distribution of such traps w as not homogeneous; its concentration in the central region of the SiO 2 film was higher than that in the regions near the surface or the int erface. The potential of monoenergetic positrons for the detection of the point defects provides unique information for depth distributions of hole traps in SiO2 films. (C) 1995 American Institute of Physics.