Molybdenum-doped indium oxide (IMO), an n-type transparent conducting oxide, was deposited using radio-frequency magnetron sputtering. The, effects of oxygen concentration in an argon ambient and substrate temperature on film properties were studied. Compared to undoped indium oxide (In2O3) films, IMO films demonstrated higher electron mobility and more than an order-of-magnitude higher carrier concentration. The highest conductivity IMO film demonstrated a mobility of 44 cm(2) V-1 s(-1) and a carrier concentration of 1.3 X 10(20) cm(-3). The properties of both In2O3 and IMO films were very sensitive to the oxygen concentration, but not to the substrate temperature. Average visible transmittance of In2O3 and, IMO films were 86% and 80%, respectively. Both optical and x-ray photoelectron spectroscopy analyses indicate a possible second phase in IMO films deposited at lower (less than or equal to1%) oxygen concentrations. (C) 2003 American Vacuum Society.