Zirconium specimens were implanted with molybdenum ions with a fluence ranging from 1 x 10(16) to 5 x 10(17) ions/cm(2) at approx. 160 degreesC using a MEVVA source at an extraction voltage of 40 kV The surfaces of the implanted samples were then analyzed and the Trim 96 computer code was used to simulate the depth distribution of molybdenum. Depth distributions of elements in the surface of samples before oxidation obtained by Auger electron spectroscopy (AES) showed that the oxide film on the zirconium substrate became thicker with increasing implantation fluence. The valence states of elements in the implanted surface layer before and after oxidation at 600 degreesC in air for 100 min were analyzed by X-ray photoelectron spectroscopy (XPS). The molybdenum, which was partially metallic in the implanted surface, was completely converted into MoO3 as a result of the heating. Glancing angle X-ray diffraction (GAXRD) at a 0.3degrees incident angle was used to examine the phase structures of implanted samples before oxidation. Tetragonal zirconia was found for a fluence of 1 x 10(16) ions/cm(2). At larger fluences both tetragonal and monoclinic zirconia were found. (C) 2003 Elsevier B.V. All rights reserved.