H. Fritzsche et al., REVERSIBLE CHANGES OF THE OPTICAL AND ELECTRICAL-PROPERTIES OF AMORPHOUS INOX BY PHOTOREDUCTION AND OXIDATION, Solar energy materials and solar cells, 32(4), 1994, pp. 383-393
The conductivity sigma of amorphous InO(x) films can be increased to m
ore than 500 OMEGA-1 cm-1 by exposure to ultraviolet light. This occur
s 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 a
t 300 K by reoxidizing the sample in ozone or an oxygen plasma. The co
nducting samples exhibit free carrier absorption below hnu = 0.2 eV an
d a Burstein shift of the optical absorption edge by about 0.4 eV. Pho
toreduction and oxidation can change the optical and electrical proper
ties of one and the same film in a reproducible manner. The temperatur
e dependence of the conductivity of different oxidation stages of a sa
mple can be explained between 150 K and 300 K by conduction in the ext
ended states of the amorphous semiconductor.