Study on the physical properties of europium doped indium oxide thin films

Structural, morphological, optical and electrical properties of europium doped In2O3 thin films grown by spray pyrolysis technique are studied in this work. The atomic percentages of europium dopant in In2O3-based solution were y = ([Eu3+][In3+])sol=0; 0.1; 0.3 and 0.5 at%. All films crystallize into the body centered cubic structure. The preferred orientation peak along the (222) plane was changed to (400) after doping. It is further revealed a best crystallinity for y =0.3 at% followed by a noticeable increase of the grain size. Some structural and microstructural parameters are determined using Rietveld refinement of XRD patterns. The optical transmission of doped films was above 68% in the visible range. The optical band gap (Eg) is in the range of [3.43-3.51] eV. Optical constant such as refractive index (n), packing density (p), porosity, oscillator energy (E0) and dispersive energy (Ed) were also studied in this report using envelope method based on transmission-reflection spectra. Electrical properties show a lowest resistivity (ρ) for a doping concentration equals to 0.3 at% reaching 0.031 Ω cm. At this doping ratio, an enhancement of free carrier concentration is also remarked. A heat treatment under nitrogen atmosphere is then applied on optimized In2O3:Eu (0.3 at%). A significant decrease of the resistivity is noted at 250 °C during 2 h reaching 0.004 Ω cm. These results lead to conclude that annealed In2O3:Eu(0.3 at%) can be a good candidate to be used in many optoelectronic devices and especially as optical window or transparent electrode in solar cells.