Freestanding diamond (FSD) film with p-type hydrogen-terminated nucleation surface was prepared by microwave plasma chemical vapour deposition (MPCVD) method. The post-treatment (wet chemical etch and annealing process) on the property of diamond film was investigated. The preparation and characterization of hydrogen-terminated diamond film p-type channel metal-semiconductor field effect transistors (MESFETs) was studied. The device was also used for photodetector application. The results showed the potential of high switching speed and high sensitivity to ultraviolet (UV).© (2010) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.