Variations of the microstructure and the optical and electrical properties with sputtering power for direct-current-magnetron-sputtered indium-doped CuO thin films at room temperature

• Published in: Thin solid films 2019-08, Vol.684, p.53-58
• Main Authors: Du, Yongli, Meng, Xue, Gao, Xiaoyong
• Format: Article
• Language: English
• Subjects: Copper oxide; Direct-current magnetron sputtering; Electrical properties; Optical properties; Thin films
• ISSN: 0040-6090; 1879-2731
• DOI: 10.1016/j.tsf.2019.05.056

Preparation of single-phased indium-doped copper oxide (CuO:In) thin films with high quality at low temperature is crucial for the commercial application of CuO-based solar cells and light-emitting devices. Herein, direct-current magnetron sputtering assisted with high sputtering power and reactive pressure technique was used to prepare monoclinic CuO:In thin films at room temperature. The influence of sputtering power (Pspu) on the microstructure and the optical and electrical properties of the films were studied. The roles of indium in the CuO:In thin films were also proposed. CuO:In thin films are single-phased and monoclinic in structure. The crystallization and the preferred 〈−111〉 orientation of the films were enhanced with increased Pspu. The red shift of the film absorption edge was due to the decrease and increase of the lattice strains along crystal axes a and b with Pspu, respectively. A conducting transition from p type to n type of the films at 100 W Pspu was closely related to the increased substitution of copper by indium. The p- and n-type conductions of the films were mainly due to the copper vacancies and interstitials oxygen and to the effective substitution of copper by indium in the films, respectively. Increased Pspu increased the free carrier concentration and decreased the mobility of the films. The free carrier concentration reached the maxima of 9.333 × 1018 /cm3 at 100 W Pspu, whereas the mobility reached the maxima of 23.38 cm2/Vs at 60 W Pspu. •Single-phased CuO:In was prepared at room temperature by DC magnetron sputtering.•Crystal lattice constants and lattice strains along crystal axes were calculated.•Red shift of the absorption edge with Pspu was explained by lattice strain.•Roles of indium in the CuO:In film was proposed.•Conducting transition from p to n was observed and explained.