F-passivated ZnO nanocrystalline films were prepared by thermal oxidation ofZnF2 films. ZnF2 films were deposited on a Si wafer by the electron beam evaporation technique. X-raydiffraction and x-ray photoelectron spectroscopy were used to study the structural changes ofZnF2 as a function of oxidation temperature. When theZnF2 film wasoxidized at 400 °C for 30 min, a polycrystalline hexagonal wurtzite structure of ZnO:F was obtained.The room temperature photoluminescence spectrum of the ZnO:F film showeda strong near band edge ultraviolet emission located at 379 nm with a narrowlinewidth of 70 meV and a very weak visible emission associated with deep leveldefects. The results demonstrated that the presence of residual F ions in ZnOnanocrystalline film can dramatically decrease the visible emission and increase theultraviolet emission of ZnO. On the basis of the experimental findings, two possiblemechanisms are proposed: (1) the residual F ions in the film occupy the lattice sites ofV o* centres (the oxygen vacancies with one electron) inside the ZnO nanocrystals, which resultsin an appreciable decrease in visible emission and (2) some of the F ions also passivate ZnOnanocrystal surface states, which prevents the holes in the valence band from being trappedin surface states and then tunnelling back into nanocrystals to combine withV o* toform V o** centres () which are another source of visible emission.