NiOx films were deposited with radio frequency (rf) magnetron sputtering at various sputtering powers (25-300 W) and deposition temperatures (room temperature to 200 degrees C) using NiO target and pure O-2 as a sputtering gas. Crystallinity, bonding state (Ni+3 and Ni+2), work function, and the resistivity of the film were measured and the performance of the pentacene thin film transistor (TFT) with the NiOx film as a source/drain (S/D) electrode was evaluated. The film properties such as roughness, work function, crystallinity, and bonding state of Ni and O were similar at each sputtering power, and the NiOx film was deposited at around 150 W and room temperature showed lower resistivity of 1.34x10(4) mu Omega cm, lower surface roughness of 0.206 nm, and higher work function of 5.2 eV. With the increase in the deposition temperature, the ratio of Ni2+ ions to Ni3+ ions in the NiOx film was increased, the work function was decreased and the resistivity was increased. A pentacene TFT with NiOx film deposited at 150 W and room temperature showed a device performance better than that with gold film, with mobility of 0.178 cm(2)/V s, threshold voltage of 0.34 V, and on/off ratio of 5.0x10(5). (C) 2008 American Vacuum Society.