Factors limiting doping efficiency of Iridium in pulsed laser deposited TiO2 transparent conducting oxide
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High transmittance and low resistivity make doped TiO2 films outstanding electrodes for use in optoelectronic devices operating in the infra-red region. In this work, we studied the impact of Ir doping in TiO2 thin films on the optoelectrical properties. High-quality nanocrystalline Ti1−x Ir x O2 thin films ~60 nm thick were grown by pulsed laser deposition from an Ir-doped target (x = 0–0.15 wt%). Films were deposited on quartz glass at a base pressure of 2 × 10−3 Pa and a substrate temperature of 780 K. The resistivity of the films decreased by 3 orders of magnitude when x increased from 0 to 0.10. The carrier mobility and concentrations increased by a factor of 2.55 from 18 to 46 cm2 V−1 s−1 at 5 %, and rose by ~2 orders of magnitude from 1019 to 1021 cm−3 at 15 % Ir, respectively. Optimal film properties were measured to be at x = 0.10, where resistivity, mobility, and carrier concentrations were 5 × 10−4 Ω cm, 32 cm2 V−1 s−1, and 1020 cm−3, respectively. The highest observed doping efficiency was ~1.1 which is similar to common dopants. At the same time, film transmittance was measured to be above 80 % in the visible and infrared regions, suitable for use in both spectral regimes. The films were characterized by X-ray diffraction, Hall transport, optical transmission, and Raman spectroscopy.
KeywordsTiO2 Carrier Concentration Pulse Laser Deposition Spark Plasma Sinter TiO2 Film
Authors would like to acknowledge Arthur W. Lichtenberger for the fruitful discussion and invaluable advice. Additional acknowledgements are extended to Michal Sabat and Keye Sun for help with experimental setup and film characterization.
This research was funded by the American Public Power Association, Demonstration of Energy & Efficiency Developments, Virginia Army National Guard, and the U.S. Army Research Laboratory under agreement number W911NF-14-2-0005 with Dr. Joe Labukas as project manager. The U.S. Government is authorized to reproduce and distribute reprints for Governmental purposes notwithstanding any copyright notation thereon.
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Conflict of interest
The authors declare that they have no conflict of interest.
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