Charge trapping and ac conductivity in Amorphous Silicon Oxide

In this paper we have studied the effect of accelerated thermal ageing on the electrical properties of amorphous silicon oxide films a-SiO2. In order to study the charge trapping phenomenon in this material, we have performed the mirror method using a secondary Electron Microscope (SEM). This method consists to inject a negative space charge in the specimen with a high energy electron beam. Results show that trapped charges increase with thermal ageing time. Dielectric investigations performed in the frequency range between 20 Hz and 1 MHz, showed that the relative permittivity increases with thermal ageing time. The ac conductivity has been found to follow the Jonsher law sigma(ac) alpha omega(n). The decrease of ac conductivity has been interpreted.