Charging, long-term-stability, and TSC-measurements of SiO2 -electrets

SiO₂ layers of different thicknesses were either thermally grown or made by chemical vapor deposition on 2-in, p-type silicon wafers. The samples were positively and negatively charged by means of liquid-contact, corona, and electron-beam methods. The surface potential decay was observed at room temperature over a period of more than one year. The positively charge SiO₂ showed a somewhat faster decay than the negatively charged material. This corresponded to open-circuit thermally stimulated current measurements, where negatively charge samples showed a higher peak temperature than positively charged samples. Positive electron-beam charging yielded a higher peak temperature than positive corona charging. Activation energies of 1.0 eV and 1.4 eV were found for positively charged oxides, whereas for negatively charged samples activation energies of about 1.9 eV were calculated