Optical and electrical properties of Sn-doped CdO thin films obtained by pulse laser deposition

Transparent tin-doped cadmium oxide (Sn–CdO) thin films with different Sn concentration were deposited on quartz glass substrates by pulse laser deposition (PLD) at 400 °C. The film’s crystallographic structure, optical and electrical properties were characterized by X-ray diffraction (XRD), field emission scanning electron microscope (FE-SEM), UV–VIS spectrophotometer and Hall system. Results show that doping of Sn enhances the film’s [111] preferred orientation and causes slight shift in the (200) Bragg angle towards higher value. The optical band gaps (Eg) of the Sn-doped films were found to increase with the increase of Sn doping concentration. In addition, proper doping of Sn evidently improves the electrical properties of CdO, such as the resistivity of the CdO film with 2.9 at% Sn doping is about one-twelfth of that of the CdO film, while the carrier concentration is about 13 times of that of the undoped. The improvements both in optical and electrical properties endow that the Sn–CdO thin films have potential application as TCO material for different optoelectronic device applications.

Research highlights
► In this study, Sn doped CdO films were deposited on quartz substrates by pulse laser deposition at the substrate temperature of 400 °C, and the effect of Sn doping concentration on the structural, optical and electrical properties of CdO films were investigated.
► The moderate Sn doping CdO film (Sn concentration of 2.9 at%) shows high carrier concentration of 4.53 × 1020 cm−3 and low electric resistivity of 1.59 × 10−4 Ω cm.
► All Sn–CdO thin films show a high optical transmission and a shift of Eg to higher energies. For their improved optical and electrical properties, Sn–CdO thin film could be an excellent candidate for future optoelectronic devices.