Effects of substrate temperature on characteristics of the p-type Ag-doped SnOx thin films prepared by reactive DC magnetron sputtering

Abstract

P-type transparent conductive oxides are one of long-persued research topics in scientific community. Substitutes for unstable p-type zinc oxide are in urgent need than ever and doped tin monoxide can be a material-of-choice. In this report, we present Ag-doped SnOx thin film produced by reactive DC magnetron sputtering from Sn + Ag alloy targets. We investigated and proved the strong influence of substrate temperatures on crystal structure, optical and electrical properties. Tin monoxide thin films showed tetragonal crystal structure and preferred diffraction peaks of (001), (101), (110), (002). As substrate temperature increased, grain size also increased, leading to reduced grain boudaries, higher hole mobility and lower resistivity. Films deposited at low (150 °C) and high (300 °C) substrate temperatures had the presence of exotic β-Sn and SnO2 phases, respectively.They acted as undesired scattering centers or induce harmful carrier recombination which decreased mobility or hole concentration. The Ag-doped SnO films fabricated at 250 °C had the best electrical properties, hole concentration 5.82 × 1018 cm−3, mobility 4.1 cm2/Vs, resistivity 2.262 × 10-1Ωcm. Current-voltage characteristics of thin film diode structures of glass/FTO/n-nc-Si:H /p-Ag:SnO/Cu and glass /FTO/n-nc-Si:H /undoped SnO/Cu were studied. They showed remarkably improved electric properties of SnO: Ag films compared to the pristine SnO counterpart.