REVERSIBLE CHANGES OF THE OPTICAL AND ELECTRICAL-PROPERTIES OF AMORPHOUS INOX BY PHOTOREDUCTION AND OXIDATION

The conductivity sigma of amorphous InO(x) films can be increased to more than 500 OMEGA-1 cm-1 by exposure to ultraviolet light. This occurs even at 100 K and in sealed samples, and is caused by photoreduction. The conductivity can be decreased to less than 10(-9) OMEGA-1 cm-1 at 300 K by reoxidizing the sample in ozone or an oxygen plasma. The conducting samples exhibit free carrier absorption below hnu = 0.2 eV and a Burstein shift of the optical absorption edge by about 0.4 eV. Photoreduction and oxidation can change the optical and electrical properties of one and the same film in a reproducible manner. The temperature dependence of the conductivity of different oxidation stages of a sample can be explained between 150 K and 300 K by conduction in the extended states of the amorphous semiconductor.