ZnO/diamond film heterojunction diodes were fabricated by depositing n-type ZnO films on p-type freestanding diamond (FSD) films using radio-frequency (RF) magnetron sputtering method. The effects of the annealing process on the properties of ZnO films were studied. The influence of the annealing process on the current-voltage (I-V) characteristics of the electrodes on ZnO and diamond films and the property of heterojunction diode was also examined. The results showed that the annealing treatment was helpful to improve the crystalline quality of the films and the performance of the diode.© (2010) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.