A new filamentary model for voltage formed amorphous oxide films

Abstract

A model is proposed to account for the conduction, negative resistance, electron emission, electro-luminescence and other features of “voltage formed” thin amorphous oxide films. This is based on the purely electronic characteristics expected from filamentary regions containing a broad impurity or defect band. Such a band of states is expected from Greene's theory of electrolytic forming in which oxygen vacancies are produced. Trapping in the localised states associated with this impurity band can increase V 0, the r.m.s. value of the random excess potential, resulting in a decrease in the available conducting non localised states. This can further result in a drastic increase in resistance at certain points along a filament. It is considered that it is the high field behaviour at such points which gives rise to the well established characteristics of these films.