Characterization of Gd doped CeO2 thin films grown by ultrasonic spray pyrolysis

Abstract

Abstract Gd concentration effect on the optical, structural, surface and electrical properties of Gd doped CeO2 thin films are coated on glass substrates by spray pyrolysis technique with precursors containing cerium nitrate hexahydrate [Ce(NO3)3·6H2O] and gadalinium nitrate hexahydrate [Gd(NO3)3·6H2O] as a source material. The structural, morphologicaly and elemental characterizations of the films have been carried out using x-ray diffraction, field emission scanning electron microscopy and energy dispersive x-ray analysis, respectively. An optical energy band gap is calculated in the range 3.3–3.8 eV from UV–Vis transmittance spectra. Surface morphologies and roughness values of the films have been investigated by atomic force microscopy. Thicknesses have been determined using spectroscopic ellipsometry technique and Cauchy–Urbach model. A four-probe setup has been used to determine the electrical resistivity values. All samples showed x-ray diffraction peaks corresponding to a cubic fluorite structure. The results indicate that the deposited films have a preferential growth in the (0 0 2) direction. The observed transmittance in the visible region has been situated between 60% and 70%. Photoluminescence spectra showed an ultraviolet emission band around 365–400 nm and the visible emission peaks between 469 and 590 nm. Raman active peaks for undoped and Gd doped CeO2 films were determined at ~465 cm−1. Finally, it has been concluded that Gd doped CeO2 films have value to work on and may be promising materials for optoelectronic applications.