Zn2– xSn1– xIn2 xO4 –d : An Indium-Substituted Spinel with Transparent Conducting Properties

Transparent conducting oxides (TCO’s) have widespread uses as electrodes in solar cells and liquid crystal displays and as heat-reflecting window coatings. The commercial TCO of choice is ITO (tin-doped indium oxide). ITO has a typical conductivity of 1!5]103 S/cm and a transparency 85—90% in thin films (1). In addition to ITO, which has been reviewed (2), a number of promising TCO’s consisting of various oxide combinations of In, Sn, and Zn have been reported (3—6). In particular, several zinc-stannate TCO’s have been reported. Enoki et al. (7) produced Zn 2 SnO 4 thin films and observed 80% transparency, a 3.20 eV band gap, and conductivities of 20 S/cm (as prepared) and 59 S/cm (reduced). In ZnOsubstituted Cd 2 SnO 4 films, Enoki et al. (8) observed worse conductivity and larger band gap as the Zn content increased. Minami et al. (9) produced an amorphous, reduced, zinc-stannate film with 200 S/cm conductivity. They suggested that the parent structure was ZnSnO 3 , although the zinc content of the film was less than 33 cation %. Palmer et al. (10) investigated ZnO/SnO 2 -cosubstituted In 2 O 3 (In 2~2x Sn x Zn x O 3~d) and found a conductivity of 2500 S/cm in a 90% In sample, but observed decreasing conductivity as In% was lowered.