The experimental result shows that the preferred orientations of NiO thin films are closely related to the working pressure of argon. All of NiO(111), NiO(200), and NiO(220) diffraction peaks are observed in the XRD patterns and exhibited random orientation of NiO film when the film is deposited in low Ar pressure of 0.67 Pa. As the Ar pressure is increased to 2.67 Pa, only the NiO(200) peak appears and shows (200)-textured NiO films. However, the lattice parameter of NiO film deposited in high Ar pressure of 2.67 Pa is 0.426 nm, which is much larger than that of the NiO bulk (0.417 nm). The lattice parameter can be reduced by post-annealing the film because the interstitial Ar atoms are released from the NiO lattice, decreasing continuously from 0.423 to 0.417 nm as the NiO films are annealed by rapid thermal annealing (RTA) from 300 to 600 degrees C. (C) 2011 Elsevier B.V. All rights reserved.