Abstract: In this paper,the transport rule of detrapped charges (either negative surface charges or positive surface and bulk charges) in the bulk of the silicon dioxide film electrets was systematically studied. The discharge behavior of silicon dioxide electret,the influence of chemical surface treatment on charge stability and the shift of charge layer in the bulk for SiO₂ were investigated. The mean charge depth can be shifted from the near free surface into the bulk of SiO₂ by control-ling the ageing temperature. The negative charges in the bulk of silicon dioxide have excellent stability,which is a very important result for the study being done about the improvement of quality for SiO₂ micro-sensors.

Key words: silicon dioxide, ageing, chemical surface treatment, electret, charge transport