Energy gaps, refractive index and photon emission from point defects in copper-doped Gd2O3 nanocrystalline films

•Reactive anodic evaporation method provides the synthesis of single-phase Gd2O3 films.•The embedding of Cu leads to a decrease in the transparency gap of Gd2O3 film.•Copper doping results to a decrease in refractive index and to an increase in its dispersion for Gd2O3 film.•The embedding of Cu into Gd2O3 stimulates the formation of lattice defects and leads to an increase in luminescence yield.•Thermally-activated energy transfer between F+ - centers and Gd3+ ions is at the heart of UV-VIS energy conversion. [Display omitted] Thin nanocrystalline films of gadolinium oxide (undoped and doped with copper ions) were synthesized by means of reactive anodic evaporation technique. Chemical composition inspection and structural-phase analysis of the samples obtained were performed by XPS and XRD methods. Optical characteristics (energy gaps, refractive index, emission parameters) of thin films were determined by means of absorption, transmission and photoluminescence spectroscopies. It was found that injection of copper leads to an insignificant decrease in the transparency gaps for direct and indirect transitions of Gd2O3 film. On the basis of interference effects, a decrease in refractive index and an increase in its dispersion in Gd2O3:Cu film were established. The excited by energy transfer from "defective" Gd3+ ions emission bands at 2.9 eV and 3.2 eV were associated with oxygen vacancies (F+- centers) localized near C2 and S6 cationic positions in Gd2O3 host. The injection of copper ions into Gd2O3 host stimulates the formation of lattice defects and leads to an increase in the luminescence yield. An analytical expression was obtained for describing luminescence flare-up and quenching. The corresponding thermal activation barriers were determined. The transfer of excitation energy between intrinsic defects of Gd2O3 film provides the conversion of hard UV radiation into soft UV and visible radiation.