KNbO3 films were prepared on Si (100) substrates by pulsed laser deposition. The effect of experimental parameters on the films structure and composition was investigated. Well crystallized and single-phase KNbO3 films were obtained at the substrate temperature of 650 degrees C, laser energy of 7.5 mJ/pulse and target-substrate distance of 40 mm, but a severe potassium-deficient was observed in the deposited films. The mechanism of K deficiency in films was explored and a method to control the composition was designed. The experimental results indicate that the composition of films can be well controlled by adjusting the oblique angle of substrates from the axial direction of plume. The stoichiometric KNbO3 films with K/Nb molar ratio of 0.98 were obtained by locating the substrate at an oblique angle of 3-12 degrees from the plume axis. (c) 2008 Elsevier B.V. All rights reserved.