Physical Properties Of Rf-Sputtered Znse Thin Films For Photovoltaic Applications: Influence Of Film Thickness

Zinc selenide (ZnSe) thin films were deposited by radio frequency magnetron sputtering onto optical glass (for structural, morphological and optical characterizations) and onto indium-tin-oxide (ITO) coated glass substrates, to be used for producing photovoltaic structures based on zinc selenide/cadmium telluride (CdTe) thin film heterojunctions. The crystalline structure of ZnSe thin films was investigated by X-ray diffraction; the films are polycrystalline with a marked (111) texture. The structure of the films deposited on glass and on ITO covered glass is analyzed comparatively. Surface morphology parameters of the films were determined by atomic force microscopy. Spectroscopic ellipsometry and optical absorption spectroscopy measurements were used to characterize the optical properties of ZnSe films. Experimentally determined band gap values were 2.83 - 2.84 eV. The temperature dependence of the electrical resistivity was investigated from room temperature down to 10 K. ITO/ZnSe/CdTe structures in superstrate configuration were produced by depositing the absorber CdTe layer by thermal vacuum evaporation (TVE). Action spectra of the external quantum efficiency (EQE) of the structures were measured before and after irradiation with protons (3 MeV), and the effect of irradiation is discussed.