Ultra thin ZnO films were prepared on metal Mo(1 1 0) substrate under ultrahigh vacuum conditions either by depositing Zn in similar to 10 (5) Pa oxygen or by oxidizing pre-deposited Zn films. The films were characterized in situ by various surface analytical techniques, including Auger electron spectroscopy, Xray and ultraviolet photoelectron spectroscopies, low energy electron diffraction and high resolution electron energy loss spectroscopy. The results indicate that a long-range ordered and stoichiometric ZnO films are formed along its [0 0 0 1] direction. The annealing experiments show that as-prepared ZnO films are thermal stable until 800 K. This study provides constructive information to further understand the growth mechanism of ZnO films on different substrates. (C) 2009 Elsevier B.V. All rights reserved.