MECHANISM OF CHARGE STORAGE IN ELECTRON-BEAM OR CORONA-CHARGED SILICON-DIOXIDE ELECTRETS

Results on investigations of 1-mu-m thick, wet-grown SiO2 as an electret material are presented in this paper. Charge decay curves at room temperature within a time period of more than three years can be given. Influences of charging methods and substrate doping on charge stability are discussed. Furthermore, measurements of charge decay in short- and open-circuit TSD experiments show some interesting phenomena which are interpreted. For example, discharge current peaks at temperatures > 250-degrees-C were found in positively charged samples. An unexpected current reversal was observed in these experiments and an explanation for this reversal can be given. Additionally the generation of traps in the bulk of SiO2 by irradiation with an electron beam is described. Applying the 'Sessler method' the mean spatial depth for these traps can be calculated. Finally, comparison of the results leads to a few conclusions about the origin of electret charges in SiO2.