Structure and transport properties of titanium oxide (Ti2O, TiO1+δ, and Ti3O5) thin films

• Published in: Journal of alloys and compounds 2019-05, Vol.786, p.607-613
• Main Authors: Fan, Yunjie, Zhang, Chao, Liu, Xiang, Lin, Yue, Gao, Guanyin, Ma, Chao, Yin, Yuewei, Li, Xiaoguang
• Format: Article
• Language: English
• Subjects: Ablation; Aluminum oxide; Electron density; Electron energy-loss spectroscopy; Hopping conduction; Oxidation; Oxygen; Oxygen content; Pulsed laser deposition; Pulsed lasers; Substrates; Superconductivity; Thin films; Titanium; Titanium oxide thin films; Titanium oxides; Transport properties
• ISSN: 0925-8388; 1873-4669
• DOI: 10.1016/j.jallcom.2019.01.381

Titanium oxides have partially filled or empty d orbital and are stable at various oxidation states with different structures and unique properties. Here, three kinds of titanium oxide thin films of hexagonal Ti2O metal, cubic TiO1+δ superconductor, and monoclinic γ-Ti3O5 semiconductor, were successfully grown on α-Al2O3 substrates by a pulsed laser deposition technique, through ablating a pure titanium target under different oxygen pressures. The electrical resistivities of these films increase with increasing oxygen content. The metallic behaviors of Ti bulk and Ti2O film can be described by the Bloch–Grüneisen formula, and the semiconducting behaviors of TiO1+δ films in normal state and γ-Ti3O5 film obey the variable range hopping and the small polaron hopping conduction mechanisms, respectively. For titanium monoxide TiO1+δ (1.05 ≤ 1+δ ≤ 1.17) films, increasing oxygen content is accompanied by an increase of disorder, a decrease of electron density of states at the Fermi level, and an enhancement of carrier localization, leading to a suppression of superconductivity. [Display omitted] •Ti2O, TiO1+δ and Ti3O5 thin films were grown by PLD using a pure titanium target.•Structures, compositions and transport properties can be tuned by oxygen contents.•The metallic hexagonal Ti2O single crystalline thin film was firstly prepared.