Substrate temperature effect on structure and properties of sputtered polycrystalline transparent conducting oxide films of La-doped BaSnO3

Abstract

Lanthanum doped barium tin oxide (LBSO) film is an impressive alternative for expensive transparent conducting oxides film such as indium tin oxide. The LBSO films are grown on quartz substrate by co-sputtering a barium tin oxide ceramic target and a lanthanum metal target in Ar/O2 plasma at different substrate temperatures ranging from 500 oC to 730 oC keeping all the other parameters constant. The resulting LBSO films are all polycrystalline in nature and their thickness varies from 520-540 nm. UV-visible absorption spectra of the films show blue shift and increasing optical band gap with increasing substrate temperatures. As the substrate temperature arises up to 650 oC, the optical transparency, Hall mobility, carrier concentration and electrical conductivity of the films all increase due to improving film crystallinity, more oxygen vacancies and higher La dopant incorporation. At optimum substrate temperatures at and above 650 oC, the representative values of optical transmittance, mobility, carrier concentration, and resistivity are ~90 %, 21 cm2/V-s, 5.5 x 1019 cm-3 and 3.4 x 10-3 Ω.cm, respectively. This understanding of varying substrate temperature effect on crystal structure, morphology, electrical, and optical properties of thin film can be further utilized to explore various transparent conducting oxide applications.