ZnO films have been grown on Si(1 1 1) substrates by metal-organic chemical vapor deposition. The Si substrates were pretreated by the Ar+ plasma bombardment before the ZnO growth for the purpose of eliminating the remnant amorphous silica layers from the substrates' surface. The effects of the plasma pretreatment on the growth of ZnO were investigated. The crystalline quality, surface morphology and photoluminescence property of the ZnO films were significantly improved by the pretreatment process. However, with increasing the plasma power, the quality of ZnO films was degraded due to the damage of the Si substrates by the bombardment. (C) 2007 Elsevier B.V. All rights reserved.