Study of nitrogen ion doping of titanium dioxide films

• Published in: Applied surface science Vol. 443; pp. 619 - 627
• Main Authors: Ramos, Raul, Scoca, Diego, Borges Merlo, Rafael, Chagas Marques, Francisco, Alvarez, Fernando, Zagonel, Luiz Fernando
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 15.06.2018; Elsevier
• Subjects: Anatase; Condensed Matter; Diffusion; Electronic transport; Materials Science; Nitrogen ion doping; Physics; Titanium dioxide; Transparent conducting oxide; Nitrogen ion doping; Anatase; Diffusion; Titanium dioxide; Electronic transport; Transparent conducting oxide; titanium dioxide; diffusion; electronic transport; nitrogen ion doping; transparent conducting oxide
• ISSN: 0169-4332; 1873-5584
• DOI: 10.1016/j.apsusc.2018.02.259

[Display omitted] •A two-step process for preparation of N:TiO2 transparent conductor is proposed.•Low energy nitrogen ions are used after Anatase thin film deposition.•Approach allows excellent control of crystal, optical and electronic properties.•Resistivity as low as 3 · 10−1 Ωcm while transparency at 550 nm is about 85%.•High temperatures enable thermal diffusion of Nitrogen inside Anatase film. This study reports on the properties of nitrogen doped titanium dioxide (TiO2) thin films considering the application as a transparent conducting oxide (TCO). Sets of thin films were prepared by sputtering a titanium target under oxygen atmosphere on a quartz substrate at 400 or 500 °C. Films were then doped at the same temperature by 150 eV nitrogen ions. The films were prepared in Anatase phase which was maintained after doping. Up to 30 at% nitrogen concentration was obtained at the surface, as determined by in situ X-ray photoelectron spectroscopy (XPS). Such high nitrogen concentration at the surface lead to nitrogen diffusion into the bulk which reached about 25 nm. Hall measurements indicate that average carrier density reached over 1019 cm−3 with mobility in the range of 0.1–1 cm2 V−1 s−1. Resistivity about 3 · 10−1 Ω cm could be obtained with 85% light transmission at 550 nm. These results indicate that low energy implantation is an effective technique for TiO2 doping that allows an accurate control of the doping process independently from the TiO2 preparation. Moreover, this doping route seems promising to attain high doping levels without significantly affecting the film structure. Such approach could be relevant for preparation of N:TiO2 transparent conducting electrodes (TCE).