Storage of optical patterns in a zinc oxide-on-silicon surface wave convolver

Summary form only given, as follows. A monolithic surface wave convolver has been used to image one-dimensional optical patterns, store them for several days, and read them out nondestructively. The configuration consists of a silicon substrate with the top surface covered by a l000A thermal oxide and a one micron sputtered piezoelectric zinc oxide film. The zinc oxide allows the excitation of surface waves on non-piezoelectric silicon using interdigi tal transducers, and creates surface wave electric fields which couple to carriers in the silicon. Changes in the carrier concentration at the silicon surface (caused for example by illumination) dramatically affect the surface wave convolution, which can thus be used to detect an optical pattern. A light pattern is stored by projecting it onto a semitransparent top convolver electrode that has an applied negative de bias. Slow states associated with the zinc oxide, probably at the zinc oxide - silicon dioxide interface, are charged in the regions exposed to the light. This charge pattern, as observed using surface wave convolution, persists for as long as five days after the light is removed. The effect has potential application for memory or improved convolution and correlation devices.