Charge and charge distributions in electron-bombarded SiO2 insulator layers

A method of determining charge distributions in electron-bombarded SiO2 layers is reported. In the experiments the Kelvin- and the HF-CV-method are used simultaneously. The measured charge distributions for 5000 A SiO2 layers showed a positive/negative structure after irradiation with 2 keV electrons at 4x1014 e/cm2. The positive part occurs at the immediate vicinity of the insulator surface, the charge density amounts up to 5x1019 e/cm3. It follows a region of negative charges with peak charge density of roughly 1019 e/cm3 between 300 and 500 A. In greater depths, after 1500 A is the charge density < 1017 e/cm3. (author)