Abstract

Thin films of indium-tin-oxide (ITO) and indium oxide (IO) were deposited on sapphire, zinc selenide, and germanium substrates to study transparent conductive coatings for the 3.5–5.0µm and 8.0–12.0µm IR region. ITO films were prepared by rf planar magnetron sputtering of an indium-tin-oxide (10% tin) target in ultrapure argon gas (99.999% purity) at a pressure of about 9 mTorr and at a substrate temperature of about 300 K. Similarly, 10 films were prepared by reactive dc planar magnetron sputtering of a pure indium (99.99% purity) target in ultrapure argon and oxygen gases at a pressure of about 9 mTorr and at a substrate temperature of about 300 K. The use of planar magnetrons to deposit thin films offers a number of advantages over other deposition systems, including high deposition rates and the ability to scale to the larger sources and substrate areas necessary for industrial applications. Both techniques of deposition of transparent conductive films show extreme hardness, chemical inertness, high electrical resistivity, and optical transparency in the 3.5–5.0µm and 8.0–12.0µm IR region. For ITO coatings, typical values obtained for coated sapphire substrate in the 3.5–5.0µm region and zinc selenide substrate in the 8.0–12.0µm region were average transmittances of 75% and 62%, and sheet resistivities of 120 ohms/square and 150 ohms/square, respectively.

© 1990 Optical Society of America