Different rare earth (Sm, La, Nd) doped magnetron sputtered CdO thin films for optoelectronic applications

Pure and rare earth elements of samarium (Sm), lanthanum (La) and neodymium (Nd) doped cadmium oxide (CdO) thin films were deposited on glass substrates by radiofrequency magnetron sputtering at room temperature. The influence of rare earth dopants on the microstructural, morphological and optoelectronic properties of the CdO thin films were studied elaborately. The X-ray diffraction studies revealed the polycrystalline with face centered cubic structure of CdO thin films. The structural defects were increased with increase of dopant's ionic radii. The presence of the dopants in host CdO thin films was confirmed by X-ray photoelectron spectroscopic analysis. The roughness of the films was decreased for the doped samples and Nd doped CdO thin film has the minimum roughness value of 1.29 nm. All the films exhibited high transmittance in visible range and well pronounced Moss-Burstein shift was observed in the band gap value. Emission bands of photoluminescence spectra depicted the presence of oxygen vacancies. Hall Effect measurement showed an increase in carrier concentration and electrical conductivity of the films with the addition of dopants. The suitable combination of high conductivity (2872 Ω⁻¹·cm⁻¹) with optical transparency (88%) and lower surface roughness of Nd doped CdO thin film, makes it a potential candidate for the transparent conducting oxide in optoelectronic devices.