Nickel oxide thin films were deposited on fused silica and Si( 1 0 0) substrates at different substrate temperatures ranging from room temperature to 400 degrees C using radio frequency reactive magnetron sputtering from a Ni metal target in a mixture of O-2 and Ar. With the increase of substrate temperature, nickel oxide films deposited on the Si substrates exhibit transition from amorphous to poly-crystalline structures with different preferred orientations of NiO(2 0 0) and (1 1 1). The films deposited at higher temperature exhibit higher Ni2+/Ni3+ ratio. With substrate temperature increasing from room temperature to 400 degrees C, the electrical resistivities of nickel oxide films increase from (2.8 +/- 0.1) x 10(-2) to (8.7 +/- 0.1) Omega cm, and the optical band-gap energies increase from 3.65 to 3.88 eV. A p-nickel oxide/n-zinc oxide heterojunction was fabricated to confirm the p-type conduction of nickel oxide thin film, which exhibited a steadily rectifying behavior. (c) 2007 Elsevier B. V. All rights reserved.