Structure, refractive index dispersion and optical absorption properties of evaporated Zn–Eu oxide films

Zn oxide, Eu oxide and Zn–Eu oxide thin films were prepared by vacuum evaporation. Their structural and optical properties have been obtained by X-ray diffractometry (XRD), energy dispersion X-ray fluorescence (EDXRF) method and spectrophotometry. The EDXRF method was used to study the composition of the deposited Zn–Eu oxide films. The XRD patterns show that the prepared thin films of Zn oxide and Zn–Eu oxide with 55% ZnO were polycrystalline, while films of Eu oxide and Zn–Eu oxide with 28% ZnO were amorphous. Spectroscopic optical constants n(λ) and k(λ) as well as energy gap Eg were evaluated from spectrophotometry in the interband transition energy region. It was observed that Zn–Eu oxide thin films remain transparent in shorter wavelength range than the ZnO thin films, resulting from the increase of their band-gap. The energy gap of ‘mixed’ oxide sample is controlled by the weight fraction of the constituent oxides. It was found that n, k and transmittance values for mixed-oxide film varies smoothly between the values of the pure constituent oxides in the fundamental energy gap region.