Photo-effects in thin oxide film sandwich structures

Abstract

Photovoltage and photocurrent studies have been made on thin oxide films of Nb, Ta, Ti and Al sandwiched between the parent metal film and a counterelectrode metal film of Au, Ag and Al. Experimental evidence for the existence in these structures of two opposing photocurrents is presented. This suggests that the observed photoeffects are due to the photoelectrons generated in the metal regions bordering the oxide structure. The polarity and magnitude of the photoeffects are determined by the absorption characteristics of the interface regions, and the intrinsic field gradient caused by the potential barriers at the interfaces. The polarity of the photovoltage and photocurrent is found to reverse with the time and direction of illumination of slightly rectifying sandwich structures. This is in accord with the hypothesis of generation of photoelectrons at the two metal-oxide interfaces.