Development of tin oxide synthesis by plasma-enhanced chemical vapor deposition

Transparent conducting oxide (TCO) thin films have been synthesized to date primarily by either physical vapor deposition or thermal chemical vapor deposition. Plasma-enhanced chemical vapor deposition (PECVD) offers potential advantages over these techniques, but it has not been applied extensively to TCO synthesis. In this article we report on the use of PECVD to deposit transparent, conducting tin oxide films from mixtures of SnCl4 and O2. These films were deposited on glass substrates at temperatures between 150 and 350 °C. The growth rate, optical, electrical, and structural properties were examined as a function of plasma power, substrate temperature, and gas composition. Increasing rf power revealed a rise in deposition rate with no effect on electrical properties, while both substrate temperature and oxygen flow rate were found to significantly influence resistivity. The effect of annealing was also examined, and it was found that annealing at 250 °C significantly improved the electrical properties. The optical transparency of all films was greater than 86% in the visible spectrum, and electrical resistivities as low as 2.1×10−3 Ω cm have been achieved.