Highly transparent conducting cerium incorporated CdO thin films deposited by a spray pyrolytic technique
Abstract
In the present work, a spray pyrolysis technique was employed to deposit cerium (Ce) doped cadmium oxide (CdO) thin films with low level doping concentrations (0.25, 0.50, 0.75 and 1.0 wt%). The crystallite size and lattice parameter values were estimated from X-ray diffraction analysis. X-ray diffraction patterns reveal the shift of preferential growth orientation from (111) to (200) planes on incorporating Ce in the CdO matrix. The oxidation state of Ce, Cd and O in the deposited films was determined by X-ray photoelectron spectroscopic (XPS) studies. Surface microstructures of the films were analyzed by atomic force microscopy and their surface nature was studied by field emission scanning electron microscopy (FE-SEM). The electrical properties of the deposited films were determined by Hall measurements in the van der Pauw configuration. The charge carrier concentration of the CdO thin film increased from 1.0 × 1020 cm−3 to 3.85 × 1020 cm−3 on doping 0.50 wt% Ce; whereas, resistivity decreased from 9.32 × 10−4 Ω cm to 3.81 × 10−4 Ω cm. The deposited Ce-doped CdO thin films for various concentrations showed an increase in the average optical transmittance to 85% from that of 72% for the CdO film in the visible and NIR region. The band gap was gradually increased from 2.38 eV to 2.63 eV due to an increase in the Ce doping at various levels. The emission properties of CdO and Ce doped CdO thin films were studied by a photoluminescence spectrum recorded at room temperature. The figure of merit estimated for 0.50 wt% of Ce doped CdO film is 9.18 × 10−3 Ω−1.
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