Influence of heat treatment on the electret properties of sol-gel prepared silicon-dioxide films

Silicon dioxide electret films are prepared by means of sol-gel processing. One of the most important factors in the preparation of sol-gel films is the heat treatment. Its influence on the electret properties of these films is studied with measurements of the isothermal surface potential decay and of the thermally stimulated discharge as well as of transmission infrared spectra and of scanning electron micrographs. After heat treatments performed at suitable high temperatures and for corresponding time periods (e.g. at 1050 degrees C for 10 min or at 800 degrees C for 16 h) after gelation, films with good electret properties are obtained with subsequent chemical surface modification and corona charging. The surface conductivity of sol-gel samples heat treated after the chemical surface modification is also investigated.