The electrical conductivity of ZnO films deposited on Si by the RF sputtering technique were modified by low-energy hydrogen implantation. Hydrogen ions were implanted at 25 keV into various ZnO films with doses ranging from 1 x 10(16) to 1.0 x 10(17) ions cm(-2). High resolution quantitative hydrogen depth profiles of the un-doped and doped samples were measured non-destructively with elastic recoil detection analysis using a finely focussed 2.5 (MeVHe+)-He-4 ion beam impinging onto the samples at 20 degrees. Structural and electrical measurements were carried out on the films by SEM, XRD and Hall probe measurements to explore the effects of hydrogen implantation. It was observed that the electrical conductivity is decreased by as much as an order of magnitude after hydrogen implantation. The films remained polycrystalline after implantation. The results suggest that reducing the n-type conductivity using low-energy hydrogen implantation without annealing may provide a pathway for passivating the donors for a possible subsequent formation of p-type acceptors by ion implantation. (c) 2005 Elsevier B.V. All rights reserved.