Electrical and luminescence properties of Zn2+ doped CuI thin films

Zn2+ doped CuI thin films were prepared by vacuum evaporation technique. The influence of the dopant on crystalline, electrical and luminescence properties of the CuI thin films were investigated. An enhancement in crystallization and the shift of (111) peak were found in the Zn2+ doped CuI films. The native p-type semiconductor of CuI film changed to n-type one for doping concentration up to 2 mol%. Such change is due to the mechanism that the Zn2+ ions not only fill the Cu vacancies but also donate free electrons. For the n-type CuI films, the minimal resistivity and maximal electron concentration was found for the 4 mol% Zn2+ doped sample. All Zn2+ doped CuI thin films showed the 410 and 422 nm near-band emissions. The intensity of the 422 nm emission was significantly improved with 1 mol% Zn2+ doping. The observation can be explained by the increase of the donor-acceptor pairs in the film.