Transparent conductive Nb-doped TiO2 films deposited by reactive dc sputtering using Ti–Nb alloy target, precisely controlled in the transition region using impedance feedback system

• Published in: Applied surface science Vol. 301; pp. 551 - 556
• Main Authors: Oka, Nobuto, Sanno, Yuta, Jia, Junjun, Nakamura, Shin-ichi, Shigesato, Yuzo
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 15.05.2014; Elsevier
• Subjects: Condensed matter: electronic structure, electrical, magnetic, and optical properties; Condensed matter: structure, mechanical and thermal properties; Cross-disciplinary physics: materials science; rheology; Exact sciences and technology; Orientation; Physics; Reactive sputtering; Thin films; TiO2-based transparent conductive oxide; Ti–Nb alloy target; Thin films; Reactive sputtering; Orientation; Ti–Nb alloy target; TiO2-based transparent conductive oxide; Inorganic compounds; Feedback; Transition element compounds; Doped materials; TiO; based transparent conductive oxide; Titanium oxide; Ti-Nb alloy target; Film growth
• ISSN: 0169-4332; 1873-5584
• DOI: 10.1016/j.apsusc.2014.02.126

•Plasma impedance feedback system was applied to a reactive sputtering using Ti-Nb alloy.•High-quality conductive Nb:TiO2 films were fabricated with high reproducibility.•Reactive sputtering can control a metal-oxygen stoichiometry of Nb:TiO2 precisely. In this study, a stable reactive sputtering process using a Ti–Nb alloy target was achieved by applying a plasma impedance feedback system. High-quality transparent conductive Nb-doped TiO2 (Nb:TiO2) films were fabricated with high reproducibility. The films were deposited on unheated substrate and subsequently annealed at 873K under vacuum conditions (below 6.0×10−4Pa) for 1h. During reactive sputtering, the feedback system precisely controlled the oxidation of the target surface in the so-called transition region. The post-annealing process yielded polycrystalline Nb:TiO2 films whose lattice defects decreased with increasing Nb concentration. An extremely low resistivity (7.2×10−4Ωcm) was achieved for Nb:TiO2 film with 60–70% transmittance in the visible region. The reactive sputtering using Ti–Nb alloys is considered to be a strong candidate for industrial-scale thin-film deposition. Furthermore, it can also control the metal-oxygen stoichiometry of Nb:TiO2 films precisely to achieve desirable properties for each industrial application.