Indium tin oxide as an optical memory material

Indium Tin Oxide (ITO) films prepared by reactive rf sputtering show excellent properties for optical recording applications in a very narrow range of oxygen partial pressure (around 4×10^–5 Torr). This narrow range is at the edge of a plateau in the electrical conductivity of the films. A small increase in the oxygen partial pressure (P(O₂)5×10^–5 Torr) causes a large and abrupt change in the electrical conductivity as well as in the structural and optical properties of these films. In addition, irradiating films at the edge of the plateau (P(O₂)4×10^–5) with a low-power pulsed laser (25 mW) yields transparent films. These results suggest that the same mechanism may be responsible for the opaque to transparent transformations observed in these experiments.