J. Semicond. > 2016, Volume 37 > Issue 2 > 022001, doi: 10.1088/1674-4926/37/2/022001
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SEMICONDUCTOR PHYSICS

Effects of reductive annealing on insulating polycrystalline thin films of Nb-doped anatase TiO2: recovery of high conductivity

Shoichiro Nakao1, 2, Yasushi Hirose1, 2, 3 and Tetsuya Hasegawa1, 2, 3

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 Corresponding author: Shoichiro Nakao, Email: tg-s-nakao@newkast.or.jp

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Abstract: We studied the effects of reductive annealing on insulating polycrystalline thin films of anatase Nb-doped TiO2 (TNO). The insulating TNO films were intentionally fabricated by annealing conductive TNO films in oxygen ambient at 400 ℃. Reduced free carrier absorption in the insulating TNO films indicated carrier compensation due to excess oxygen. With H2-annealing, both carrier density and Hall mobility recovered to the level of conducting TNO, demonstrating that the excess oxygen can be efficiently removed by the annealing process without introducing additional scattering centers.

Key words: transparent conductive oxide, Nb-doped TiO2, pulsed laser deposition



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Fig. 1.  (a) Resistivity ($\rho$) of epitaxial (squares) and polycrystalline (circles) Nb-doped TiO$_{2}$ (TNO) films. The pristine polycrystalline film was post-annealed in O$_{2}$ and H$_{2}$ at 400 ℃ repeatedly. The data of the epitaxial film are from Reference [16]. (b) Transmittance spectra of the polycrystalline TNO films (pristine and after post-deposition annealing in O$_{2}$ and H$_{2}$ ambient).

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Fig. 2.  (a) $\rho$, (b) carrier density ($n_{\rm e})$, and (c) Hall mobility ($\mu$) of the polycrystalline TNO films annealed at various temperatures in H$_{2}$ ambient. Before H$_{2}$-annealing, the TNO films showed high $\rho$ values of 10--100 $\upOmega \cdot$cm due to excess oxygen. The dashed lines represent the pristine values before O$_{2}$-annealing.

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Fig. 3.  X-ray diffraction (XRD) patterns of the pristine film and the film annealed at 600 ℃ in H$_{2}$ ambient. Before H$_{2}$-annealing, the films showed high $\rho$ values due to excess oxygen.

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    Received: 13 October 2015 Revised: Online: Published: 01 February 2016

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      Article Navigation >  Journal of Semiconductors  > 2016  >  37(2): 022001
      Shoichiro Nakao, Yasushi Hirose, Tetsuya Hasegawa. Effects of reductive annealing on insulating polycrystalline thin films of Nb-doped anatase TiO2: recovery of high conductivity[J]. Journal of Semiconductors, 2016, 37(2): 022001. doi: 10.1088/1674-4926/37/2/022001 S Nakao, Y Hirose, T Hasegawa. Effects of reductive annealing on insulating polycrystalline thin films of Nb-doped anatase TiO2: recovery of high conductivity[J]. J. Semicond., 2016, 37(2): 022001. doi: 10.1088/1674-4926/37/2/022001.Export: BibTex EndNote
      Citation:
      Shoichiro Nakao, Yasushi Hirose, Tetsuya Hasegawa. Effects of reductive annealing on insulating polycrystalline thin films of Nb-doped anatase TiO2: recovery of high conductivity[J]. Journal of Semiconductors, 2016, 37(2): 022001. doi: 10.1088/1674-4926/37/2/022001

      S Nakao, Y Hirose, T Hasegawa. Effects of reductive annealing on insulating polycrystalline thin films of Nb-doped anatase TiO2: recovery of high conductivity[J]. J. Semicond., 2016, 37(2): 022001. doi: 10.1088/1674-4926/37/2/022001.
      Export: BibTex EndNote
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      Effects of reductive annealing on insulating polycrystalline thin films of Nb-doped anatase TiO2: recovery of high conductivity

      doi: 10.1088/1674-4926/37/2/022001
      • 1.

        Kanagawa Academy of Science and Technology (KAST), Kawasaki 213-0012, Japan

      • 2.

        Japan Science and Technology Agency, CREST, Bunkyo, Tokyo 113-0033, Japan

      • 3.

        Department of Chemistry, The University of Tokyo, Bunkyo, Tokyo 113-0033, Japan

      Funds:

      Project supported by the National Natural Science Foundation of China (No. 10974077) and the Innovation Project of Shandong Graduate Education, China (No. SDYY13093).

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      • Corresponding author: Email: tg-s-nakao@newkast.or.jp
      • Received Date: 2015-10-13
      • Published Date: 2016-01-25

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