PREPARATION AND DOPING OF ZINC-OXIDE USING SPRAY-PYROLYSIS

ZnO conductive layers were prepared using spray pyrolysis in air, at a substrate temperature of 150 degrees C. Doping was achieved using B, Al, Ga, In, As, Fe, La, Gd, and Mo. As-sprayed undoped ZnO films had a resistivity of 3.5 (+/-2) x 10(4) Omega cm. Hydrogen anneal at 350 degrees C for 5 min reduced the resistivity of most films by several orders of magnitude, and resistivities in the 10(-3) Omega cm range were obtained for films doped with Al and In and 10(-2) Omega cm with Ga, Mo, and B. The films have a high degree of transparency, 80-90%, even when doped and annealed in hydrogen. The bandgap was measured to be 3.22eV and was unaffected by doping with Al and B, by annealing in hydrogen and by substrate temperature. AFM and STM images show crystallinity of the films. Carrier concentration ranged up to 10(21) cm(-3) and mobilities up to 30 cm(2) s(-1) V-1. ZnO was spray deposited on top of CdS films without destroying the CdS films. This film was then annealed in hydrogen and the resulting ZnO/CdS film was measured for conductivity in the range of 10(-2) Omega cm.