A CeO₂ film with a thickness of about 80 nm was deposited by a mass-analysed low-energy dual ion beam deposition technique on an Si(111) substrate. Reflection high-energy electron diffraction and x-ray diffraction measurements showed that the film is a single crystal. The tetravalent state of Ce in the film was confirmed by x-ray photoelectron spectroscopy measurements, indicating that stoichiometric CeO₂ was formed. Violet/blue light emission (379.5 nm) was observed at room temperature, which may be tentatively explained by charge transitions from the 4f band to the valence band of CeO₂.