Hostname: page-component-8448b6f56d-mp689 Total loading time: 0 Render date: 2024-04-19T04:03:37.073Z Has data issue: false hasContentIssue false
  • English
  • Français

Hydrogen in oxide semiconductors

Published online by Cambridge University Press:  18 May 2012

Matthew D. McCluskey ,
Marianne C. Tarun  and
Samuel T. Teklemichael
Matthew D. McCluskey*
Affiliation:
Department of Physics and Astronomy, Washington State University, Pullman, Washington 99164-2814
Marianne C. Tarun
Affiliation:
Department of Physics and Astronomy, Washington State University, Pullman, Washington 99164-2814
Samuel T. Teklemichael
Affiliation:
Department of Physics and Astronomy, Washington State University, Pullman, Washington 99164-2814
*
a)Address all correspondence to this author. e-mail: mattmcc@wsu.edu
Get access

Abstract

Oxide semiconductors exhibit a range of physical properties and have potential optical, electronic, and energy applications. Transparent conducting oxides (TCOs) are currently used in products such as flat-panel displays. The prevailing n-type conductivity in these materials has historically been attributed to native defects such as oxygen vacancies. Recent calculations and experiments, however, have provided evidence that native defects are actually not responsible in majority of the cases. Hydrogen, on the other hand, does act as a shallow donor and can dramatically affect the electrical properties of oxides. In addition to contributing to n-type doping, hydrogen also passivates dangling bonds in cation vacancies and passivates acceptor dopants. Some oxides contain “hidden hydrogen,” perhaps H2 molecules, which dissociate at elevated temperatures. In this article, the many roles of hydrogen in zinc oxide, tin dioxide, titanium dioxide, indium (III) oxide, gallium (III) oxide, and strontium titanate are reviewed. The emphasis is on fundamental electronic, structural, and vibrational properties of hydrogen complexes, as determined by experiment and theory.

Keywords

hydrogenationoxideinfrared (IR) spectroscopy
Type
Reviews
Information
Journal of Materials Research , Volume 27 , Issue 17: Focus Issue: Oxide Semiconductors , 14 September 2012 , pp. 2190 - 2198
Copyright
Copyright © Materials Research Society 2012

Access options

Get access to the full version of this content by using one of the access options below. (Log in options will check for institutional or personal access. Content may require purchase if you do not have access.)

References

REFERENCES

1.Ramesh, R. and Schlom, D.G.: Whither oxide electronics? MRS Bull. 33(11), 1006 (2008).CrossRefGoogle Scholar
2.Bednorz, J.G. and Müller, K.A.: Possible high T c superconductivity in the Ba-La-Cu-O system. Z. Phys. B: Condens. Matter 64, 189–193 (1986).CrossRefGoogle Scholar
3.Dawber, M., Rabe, K.M., and Scott, J.F.: Physics of thin-film ferroelectric oxides. Rev. Mod. Phys. 77, 1083–1130 (2005).CrossRefGoogle Scholar
4.Ramirez, A.P.: Colossal magnetoresistance. J. Phys. Condens. Matter 9, 8171 (1997).CrossRefGoogle Scholar
5.Ohtomo, A. and Hwang, H.Y.: A high-mobility electron gas at the LaAlO3/SrTiO3 heterointerface. Nature 427, 423–426 (2004).CrossRefGoogle ScholarPubMed
6.Facchetti, A. and Marks, T., editors: Transparent Electronics: From Synthesis to Applications (Wiley, New York, 2010).CrossRefGoogle Scholar
7.Kawazoe, H., Yanagi, H., Ueda, K., and Hosono, H.: Transparent p-type conducting oxides: Design and fabrication of p-n heterojunctions. MRS Bull. 25(8), 28 (2000).CrossRefGoogle Scholar
8.Ginley, D.S. and Bright, C.: Transparent conducting oxides. MRS Bull. 25(8), 15–18 (2000).CrossRefGoogle Scholar
9.Tiwari, A.N., Khrypunov, G., Kurdzesau, F., Bätzner, D.L., Romeo, A., and Zogg, H.: CdTe solar cell in a novel configuration. Prog. Photovoltaics Res. Appl. 12, 33–38 (2004).CrossRefGoogle Scholar
10.Minami, T.: New n-type transparent conducting oxides. MRS Bull. 25(8), 38 (2000).CrossRefGoogle Scholar
11.King, P.D.C. and Veal, T.D.: Conductivity in transparent oxide semiconductors. J. Phys. Condens. Matter 23, 334214:1–17 (2011).CrossRefGoogle ScholarPubMed
12.Hartnagel, H.L., Dawar, A.L., Jain, A.K., and Jagadish, C.: Semiconducting Transparent Thin Films (Institute of Physics, London, 1995).Google Scholar
13.Varley, J.B., Peelaers, H., Janotti, A., and Van de Walle, C.G.: Hydrogenated cation vacancies in semiconducting oxides. J. Phys. Condens. Matter 23, 334212:1–9 (2011).CrossRefGoogle ScholarPubMed
14.King, P.D.C., Veal, T.D., Payne, D.J., Bourlange, A., Egdell, R.G., and McConville, C.F.: Surface electron accumulation and the charge neutrality level in In2O3. Phys. Rev. Lett. 101, 116808:1–4 (2008).CrossRefGoogle ScholarPubMed
15.Lany, S., Zakutayev, A., Mason, T.O., Wager, J.F., Poeppelmeier, K.R., Perkins, J.D., Berry, J.J., Ginley, D.S., and Zunger, A.: Surface origin of high conductivities in undoped In2O3 thin films. Phys. Rev. Lett. 108, 016802:1–4 (2012).CrossRefGoogle ScholarPubMed
16.Schmidt, O., Kiesel, P., Van de Walle, C.G., Johnson, N.M., Nause, J., and Döhler, G.H.: Effects of an electrically conducting layer at the zinc oxide surface. Jpn. J. Appl. Phys. 44, 7271–7274 (2005).CrossRefGoogle Scholar
17.Look, D.C., Mosbacker, H.L., Strzhemechny, Y.M., and Brillson, L.J.: Effects of surface conduction on hall-effect measurements in ZnO. Superlattices Microstruct. 38, 406–412 (2005).CrossRefGoogle Scholar
18.Eranna, G.: Metal Oxide Nanostructures as Gas Sensing Devices (CRS Press, Boca Raton, FL, 2012).Google Scholar
19.Shalish, I., Temkin, H., and Narayanamurti, V.: Size-dependent surface luminescence in ZnO nanowires. Phys. Rev. B 69, 245401:1–4 (2004).CrossRefGoogle Scholar
20.Teklemichael, S.T. and McCluskey, M.D.: Acceptor and surface states of ZnO nanocrystals: A unified model. Nanotechnology 22, 475703:1–4 (2011).CrossRefGoogle ScholarPubMed
21.Hlaing Oo, W.M., McCluskey, M.D., Huso, J., and Bergman, L.: Infrared and Raman spectroscopy of ZnO nanoparticles annealed in hydrogen. J. Appl. Phys. 102, 043529:1–5 (2007).CrossRefGoogle Scholar
22.Singhal, S.C.: Science and technology of solid-oxide fuel cells. MRS Bull. 25(3), 16–21 (2000).CrossRefGoogle Scholar
23.Norby, T.: Proton conductivity in perovskite oxides, in Perovskite Oxides for Solid Oxide Fuel Cells, edited by Ishihara, T. (Springer, New York, NY, 2009); pp.217–241.CrossRefGoogle Scholar
24.Fujishima, A. and Honda, K.: Electrochemical photolysis of water at a semiconductor electrode. Nature 238, 37–38 (1972).CrossRefGoogle Scholar
25.Osterloh, F.E.: Inorganic materials as catalysts for photochemical splitting of water. Chem. Mater. 20, 35 (2008).CrossRefGoogle Scholar
26.Van de Walle, C.G. and Neugebauer, J.: Universal alignment of hydrogen levels in semiconductors, insulators and solutions. Nature 423, 626–628 (2003).CrossRefGoogle ScholarPubMed
27.Kiliç, Ç. and Zunger, A.: n-type doping of oxides by hydrogen. Appl. Phys. Lett. 81, 73–75 (2002).CrossRefGoogle Scholar
28.Lichti, R.L., Chow, K.H., and Cox, S.F.J.: Hydrogen defect-level pinning in semiconductors: The muonium equivalent. Phys. Rev. Lett. 101, 136403:1–4 (2008).CrossRefGoogle ScholarPubMed
29.King, P.D.C., Lichti, R.L., Celebi, Y.G., Gil, J.M., Vilão, R.C., Alberto, H.V., Piroto Duarte, J., Payne, D.J., Egdell, R.G., McKenzie, I., McConville, C.F., Cox, S.F.J., and Veal, T.D.: Shallow donor state of hydrogen in In2O3 and SnO2: Implications for conductivity in transparent conducting oxides. Phys. Rev. B 80, 081201(R):1–4 (2009).CrossRefGoogle Scholar
30.Cox, S.F.J., Lord, J.S., Cottrell, S.P., Gil, J.M., Alberto, H.V., Keren, A., Prabhakaran, D., Scheuermann, R., and Stoykov, A.: Oxide muonics: I. Modelling the electrical activity of hydrogen insemiconducting oxides. J. Phys. Condens. Matter 18, 1061–1078 (2006).CrossRefGoogle Scholar
31.King, P.D.C., McKenzie, I., and Veal, T.D.: Observation of shallow-donor muonium in Ga2O3: Evidence for hydrogen-induced conductivity. Appl. Phys. Lett. 96, 062110:1–3 (2010).CrossRefGoogle Scholar
32.Xiong, K., Robertson, J., and Clark, S.J.: Behavior of hydrogen in wide band gap oxides. J. Appl. Phys. 102, 083710:1–13 (2007).CrossRefGoogle Scholar
33.Özgür, Ü., Alivov, Ya.I., Liu, C., Teke, A., Reshchikov, M.A., Doğan, S., Avrutin, V., Cho, S-J., and Morkoç, H.: A comprehensive review of ZnO materials and devices. J. Appl. Phys. 98, 041301:1–103 (2005).CrossRefGoogle Scholar
34.Pearton, S.J., Norton, D.P., Ip, K., Heo, Y.W., and Steiner, T.: Recent advances in processing of ZnO. J. Vac. Sci. Technol., B 22, 932–948 (2004).CrossRefGoogle Scholar
35.Nuruddin, A. and Abelson, J.R.: Improved transparent conductive oxide/p(+)/i junction in amorphous silicon solar cells by tailored hydrogen flux during growth. Thin Solid Films 394, 49–63 (2001).CrossRefGoogle Scholar
36.Wager, J.F.: Transparent electronics. Science 300, 1245–1246 (2003).CrossRefGoogle ScholarPubMed
37.McCluskey, M.D. and Jokela, S.J.: Defects in ZnO. J. Appl. Phys. 106, 071101:1–13 (2009).CrossRefGoogle Scholar
38.Kohan, A.F., Ceder, G., Morgan, D., and Van de Walle, C.G.: First-principles study of native point defects in ZnO. Phys. Rev. B 61, 15019–15027 (2000).CrossRefGoogle Scholar
39.Erhard, P., Albe, K., and Kelin, A.: First-principles study of intrinsic point defects in ZnO: Role of band structure, volume relaxation, and finite-size effects. Phys. Rev. B 73, 205203:1–9 (2006).CrossRefGoogle Scholar
40.Lany, S. and Zunger, A.: Dopability, intrinsic conductivity, and nonstoichiometry of transparent conducting oxides. Phys. Rev. Lett. 98, 045501:1–4 (2007).CrossRefGoogle ScholarPubMed
41.Paudel, T.R. and Lambrecht, W.R.L.: First-principles calculation of the O vacancy in ZnO: A self-consistent gap-corrected approach. Phys. Rev. B 77, 205202:1–9 (2008).CrossRefGoogle Scholar
42.Vlasenko, L.S. and Watkins, G.D.: Optical detection of electron paramagnetic resonance for intrinsic defects produced in ZnO by 2.5-MeV electron irradiation in situ at 4.2 K. Phys. Rev. B 72, 035203:1–12 (2005).CrossRefGoogle Scholar
43.Evans, S.M., Giles, N.C., Halliburton, L.E., and Kappers, L.A.: Further characterization of oxygen vacancies and zinc vacancies in electron-irradiated ZnO. J. Appl. Phys. 103, 043710:1–7 (2008).CrossRefGoogle Scholar
44.Janotti, A. and Van de Walle, C.G.: Native point defects in ZnO. Phys. Rev. B 76, 165202:1–22 (2007).CrossRefGoogle Scholar
45.McCluskey, M.D., Jokela, S.J., Zhuravlev, K.K., Simpson, P.J., and Lynn, K.G.: Infrared spectroscopy of hydrogen in ZnO. Appl. Phys. Lett. 81, 3807–3809 (2002).CrossRefGoogle Scholar
46.Lavrov, E.V., Weber, J., Börrnert, F., Van de Walle, C.G., and Helbig, R.: Hydrogen-related defects in ZnO studied by infrared absorption spectroscopy. Phys. Rev. B 66, 165205:1–7 (2002).CrossRefGoogle Scholar
47.McCluskey, M.D. and Jokela, S.J.: Sources of n-type conductivity in ZnO. Physica B 401–402, 355–357 (2007).CrossRefGoogle Scholar
48.Li, X.B., Limpijumnong, S., Tian, W.Q., Sun, H.B., and Zhang, S.B.: Hydrogen in ZnO revisited: Bond center versus antibonding site. Phys. Rev. B 78, 113203:1–4 (2008).CrossRefGoogle Scholar
49.Bang, J., Choi, E-A., and Chang, K.J.: The effect of impurities on hydrogen bonding site and local vibrational frequency in ZnO. J. Appl. Phys. 106, 053522:1–5 (2009).CrossRefGoogle Scholar
50.Jokela, S.J. and McCluskey, M.D.: Structure and stability of O–H donors in ZnO from high-pressure and infrared spectroscopy. Phys. Rev. B 72, 113201:1–4 (2005).CrossRefGoogle Scholar
51.Shi, G.A., Saboktakin, M., Stavola, M., and Pearton, S.J.: “Hidden hydrogen” in as-grown ZnO. Appl. Phys. Lett. 85, 5601–5603 (2004).CrossRefGoogle Scholar
52.Lavrov, E.V., Herklotz, F., and Weber, J.: Identification of hydrogen molecules in ZnO. Phys. Rev. Lett. 102, 185502:1–4 (2009).CrossRefGoogle ScholarPubMed
53.Janotti, A. and Van de Walle, C.G.. Hydrogen multicenter bonds. Nat. Mater. 6, 44–47 (2007).CrossRefGoogle Scholar
54.Meyer, B.K., Alves, H., Hoffman, D.M., Kriegseis, W., Forster, D., Bertram, F., Christen, J., Hoffman, A., Strassburg, M., Dworzak, M., Haboeck, U., and Rodina, A.V.: Bound exciton and donor-acceptor pair recombinations in ZnO. Phys. Status Solidi B 241, 231–260 (2004).CrossRefGoogle Scholar
55.Lavrov, E.V., Herklotz, F., and Weber, J.: Identification of two hydrogen donors in ZnO. Phys. Rev. B 79, 165210:1–13 (2009).CrossRefGoogle Scholar
56.Gärtner, F.G. and Mollwo, E.: IR absorption of OH and OD centers and OH/OH, OD/OD, and OH/OD complexes in Cu-doped ZnO single crystals. Phys. Status Solidi B 89, 381–388 (1978).CrossRefGoogle Scholar
57.Halliburton, L.E., Wang, L.J., Bai, L.H., Garces, N.Y., Giles, N.C., Callahan, M.J., and Wang, B.G.: Infrared absorption from OH− ions adjacent to lithium acceptors in hydrothermally grown ZnO. J. Appl. Phys. 96, 7168–7172 (2004).CrossRefGoogle Scholar
58.Shi, G.A., Stavola, M., and Beall Fowler, W.: Identification of an OH–Li center in ZnO: Infrared absorption spectroscopy and density functional theory. Phys. Rev. B 73, 081201:1–3 (2006).CrossRefGoogle Scholar
59.Jokela, S.J. and McCluskey, M.D.: Unambiguous identification of nitrogen–hydrogen complexes in zinc oxide. Phys. Rev. B 76, 193201:1–4 (2007).CrossRefGoogle Scholar
60.Kumar, O.S., Watanabe, E., Nakai, R., Nishimoto, N., and Fujita, Y.: Growth of nitrogen-doped ZnO films by MOVPE using diisopropyl zinc and tertiary-butanol. J. Cryst. Growth 298, 491–494 (2007).CrossRefGoogle Scholar
61.Jokela, S.J. and McCluskey, M.D.: Structure and stability of N–H complexes in single-crystal ZnO. J. Appl. Phys. 107, 113536:1–5 (2010).CrossRefGoogle Scholar
62.Li, X., Keyes, B., Asher, S., Zhang, S.B., Wei, S-H., Coutts, T.J., Limpijumnong, S., and Van de Walle, C.G.: Hydrogen passivation effect in nitrogen-doped ZnO thin films. Appl. Phys. Lett. 86, 122107:1–3 (2005).CrossRefGoogle Scholar
63.Lyons, J.L., Janotti, A., and Van de Walle, C.G.: Why nitrogen cannot lead to p-type conductivity in ZnO. Appl. Phys. Lett. 95, 252105:1–3 (2009).CrossRefGoogle Scholar
64.Lany, S. and Zunger, A.: Generalized Koopmans density functional calculations reveal the deep acceptor state of NO in ZnO. Phys. Rev. B 81, 205209:1–5 (2010).CrossRefGoogle Scholar
65.Tarun, M.C., Zafar Iqbal, M., and McCluskey, M.D.: Nitrogen is a deep acceptor in ZnO. AIP Adv. 1, 022105:1–7 (2011).CrossRefGoogle Scholar
66.Mollwo, E.: The effect of hydrogen on the conductivity and luminescence of zincoxide crystals. Z. Phys. 138, 478–488 (1954).CrossRefGoogle Scholar
67.Thomas, D.G. and Lander, J.J.: Hydrogen as a donor in zinc oxide. J. Chem. Phys. 25, 1136–1142 (1956).CrossRefGoogle Scholar
68.Nickel, N.H.: Hydrogen migration in single crystal and polycrystalline zinc oxide. Phys. Rev. B 73, 195204:1–9 (2006).CrossRefGoogle Scholar
69.Wardle, M.G., Goss, J.P., and Briddon, P.R.: First-principles study of the diffusion of hydrogen in ZnO. Phys. Rev. Lett. 96, 205504:1–4 (2006).CrossRefGoogle ScholarPubMed
70.Bang, J. and Chang, K.J.: Diffusion and thermal stability of hydrogen in ZnO. Appl. Phys. Lett. 92, 132109:1–3 (2008).CrossRefGoogle Scholar
71.Batzill, M. and Diebold, U.: The surface and materials science of tin oxide. Prog. Surf. Sci. 79, 47–154 (2005).CrossRefGoogle Scholar
72.Delahoy, A.E. and Guo, S.: Transparent conducting oxides for photovoltaics. In Handbook of Photovoltaic Science and Engineering, 2nd ed.; Luque, A. and Hegedus, S. ed.; John Wiley & Sons Ltd., UK, 2011; pp. 716–796.Google Scholar
73.Anscombe, N.: Solar cells that mimic plants. Nat. Photonics 5, 266–267 (2011).CrossRefGoogle Scholar
74.Presley, R.E., Munsee, C.L., Park, C-H., Hong, D., Wager, J.F., and Keszler, D.A.: Tin oxide transparent thin-film transistors. J. Phys. D 37, 2810–2813 (2004).CrossRefGoogle Scholar
75.Lewis, B.G. and Paine, D.C.: Applications and processing of transparent conducting oxides. MRS Bull. 25(8), 22–27 (2000).CrossRefGoogle Scholar
76.Gordon, R.G.: Criteria for choosing transparent conductors. MRS Bull. 25(8), 52–57 (2000).CrossRefGoogle Scholar
77.Göpel, W. and Schierbaum, K.D.: SnO2 sensors: Current status and future prospects. Sens. Actuators, B 26–27, 1–12 (1995).CrossRefGoogle Scholar
78.Lu, F., Liu, Y., Dong, M., and Wang, X.: Nanosized tin oxide as the novel material with simultaneous detection towards CO, H2 and CH4. Sens. Actuators, B 66, 225–227 (2000).CrossRefGoogle Scholar
79.Singh, A.K., Janotti, A., Scheffler, M., and Van de Walle, C.G.: Sources of electrical conductivity in SnO2. Phys. Rev. Lett. 101, 055502:1–4 (2008).CrossRefGoogle ScholarPubMed
80.Hlaing Oo, W.M., Tabatabaei, S., McCluskey, M.D., Varley, J.B., Janotti, A., and Van de Walle, C.G.: Hydrogen donors in SnO2 studied by infrared spectroscopy and first-principles calculations. Phys. Rev. B 82, 193201:1–4 (2010).CrossRefGoogle Scholar
81.Bekisli, F., Stavola, M., Beall Fowler, W., Boatner, L., Spahr, E., and Lüpke, G.: Hydrogen impurities and shallow donors in SnO2 studied by infrared spectroscopy. Phys. Rev. B 84, 035213:1–8 (2011).CrossRefGoogle Scholar
82.Varley, J.B., Janotti, A., Singh, A.K., and Van de Walle, C.G.: Hydrogen interactions with acceptor impurities in SnO2: First-principles calculations. Phys. Rev. B 79, 245206:1–4 (2009).CrossRefGoogle Scholar
83.Kavan, L., Grätzel, M., Gilbert, S.E., Klemenz, C., and Scheel, H.J.: Electrochemical and photoelectrochemical investigation of single-crystal anatase. J. Am. Chem. Soc. 118, 6716–6723 (1996).CrossRefGoogle Scholar
84.Diebold, U.: The surface science of titanium dioxide. Surf. Sci. Rep. 48, 53–229 (2003).CrossRefGoogle Scholar
85.Ojamäe, L., Aulin, C., Pedersen, H. and Käll, P-O.: IR and quantum-chemical studies of carboxylic acid and glycine adsorption on rutile TiO2 nanoparticles. J. Colloid Interface Sci. 296, 71–78 (2006).CrossRefGoogle ScholarPubMed
86.Grätzel, M.: Photoelectrochemical cells. Nature 414, 338–344 (2001).CrossRefGoogle ScholarPubMed
87.O’Regan, B. and Grätzel, M.: A low-cost, high-efficiency solar cell based on dye-sensitized colloidal TiO2 films. Nature 353, 737–740 (1991).CrossRefGoogle Scholar
88.Soffer, B.: Studies of the optical and infrared absorption spectra of rutile single crystals. J. Chem. Phys. 35, 940–945 (1961).CrossRefGoogle Scholar
89.Herklotz, F., Lavrov, E.V., and Weber, J.: Infrared absorption of the hydrogen donor in rutile TiO2. Phys. Rev. B 83, 235202:1–5 (2011).CrossRefGoogle Scholar
90.Filippone, F., Mattioli, G., Alippi, P., and Amore Bonapasta, A.: Properties of hydrogen and hydrogen-vacancy complexes in the rutile phase of titanium dioxide. Phys. Rev. B 80, 245203:1–8 (2009).CrossRefGoogle Scholar
91.Peacock, P.W. and Robertson, J.: Behavior of hydrogen in high dielectric constant oxide gate insulators. Appl. Phys. Lett. 83, 2025–2027 (2003).CrossRefGoogle Scholar
92.Bjørheim, T.S., Stølen, S., and Norby, T.: Ab initio studies of hydrogen and acceptor defects in rutile TiO2. Phys. Chem. Chem. Phys. 12, 6817–6825 (2010).CrossRefGoogle Scholar
93.Spahr, E.J., Wen, L., Stavola, M., Boatner, L.A., Feldman, L.C., Tolk, N.H., and Lüpke, G.: Giant enhancement of hydrogen transport in rutile TiO2 at low temperatures. Phys. Rev. Lett. 104, 205901:1–4 (2010).CrossRefGoogle ScholarPubMed
94.Cho, E., Han, S., Ahn, H-S., Lee, K-R., Kim, S.K., and Hwang, C.S.: First-principles study of point defects in rutile TiO2−x. Phys. Rev. B 73, 193202:1–4 (2006).CrossRefGoogle Scholar
95.Bourlange, A., Payne, D.J., Egdell, R.G., Foord, J.S., Edwards, P.P., Jones, M.O., Schertel, A., Dobson, P.J., and Hutchison, J.L.: Growth of In2O3(100) on Y-stabilized ZrO2(100) by O-plasma assisted molecular beam epitaxy. Appl. Phys. Lett. 92, 092117:1–3 (2008).CrossRefGoogle Scholar
96.Koida, T., Fujiwara, H., and Kondo, M.: Hydrogen-doped In2O3 as high-mobility transparent conductive oxide. Jpn. J. Appl. Phys. 46, L685–L687 (2007).CrossRefGoogle Scholar
97.Limpijumnong, S., Reunchan, P., Janotti, A., and Van de Walle, C.G.: Hydrogen doping in indium oxide: An ab initio study. Phys. Rev. B 80, 193202:1–4 (2009).CrossRefGoogle Scholar
98.Shukla, S., Seal, S., Ludwig, L., and Parish, C.: Nanocrystalline indium oxide-doped tin oxide thin film as low temperature hydrogen sensor. Sens. Actuators, B 97, 256–265 (2004).CrossRefGoogle Scholar
99.Reunchan, P., Zhou, X., Limpijumnong, S., Janotti, A., and Van de Walle, C.G.: Vacancy defects in indium oxide: An ab-initio study. Curr. Appl Phys. 11, S296–S300 (2011).CrossRefGoogle Scholar
100.Orita, M., Ohta, H., Hirano, M., and Hosono, H.: Deep-ultraviolet transparent conductive β-Ga2O3 thin films. Appl. Phys. Lett. 77, 4166–4168 (2000).CrossRefGoogle Scholar
101.Varley, J.B., Weber, J.R., Janotti, A., and Van de Walle, C.G.: Oxygen vacancies and donor impurities in β-Ga2O3. Appl. Phys. Lett. 97, 142106:1–3 (2010).CrossRefGoogle Scholar
102.van Benthem, K., Elsässer, C., and French, R.H.: Bulk electronic structure of SrTiO3: Experiment and theory. J. Appl. Phys. 90, 6156–6164 (2001).CrossRefGoogle Scholar
103.Kawai, M., Watanabe, S., and Hanada, T.: Molecular beam epitaxy of Bi2Sr2CuOx and Bi2Sr2Ca0.85Sr0.15Cu2Ox ultra thin films at 300°C. J. Cryst. Growth 112, 745–752 (1991).CrossRefGoogle Scholar
104.Kan, D., Terashima, T., Kanda, R., Masuno, A., Tanaka, K., Chu, S., Kan, H., Ishizumi, A., Kanemitsu, Y., Shimakawa, Y., and Takano, M.: Blue-light emission at room temperature from Ar+-irradiated SrTiO3. Nat. Mater. 4, 816–819 (2005).CrossRefGoogle Scholar
105.Houde, D., Lépine, Y., Pépin, C., Jandl, S., and Brebner, J.L.: High-resolution infrared spectroscopy of hydrogen impurities in strontium titanate. Phys. Rev. B 35, 4948–4953 (1987).CrossRefGoogle ScholarPubMed
106.Son, J., Moetakef, P., Jalan, B., Bierwagen, O., Wright, N.J., Engel-Herbert, R., and Stemmer, S.: Epitaxial SrTiO3 films with electron mobilities exceeding 30,000 cm2V−1s−1. Nat. Mater. 9, 482–484 (2010).CrossRefGoogle Scholar
107.Higuchi, T., Tsukamoto, T., Sata, N., Ishigame, M., Tezuka, Y., and Shin, S.: Electronic structure of p-type SrTiO3 by photoemission spectroscopy. Phys. Rev. B 57, 6978–6983 (1998).CrossRefGoogle Scholar
108.Fix, T., Bali, R., Stelmashenko, N., and Blamire, M.G.: Influence of the dopant concentration in In-doped SrTiO3 on the structural and transport properties. Solid State Commun. 146, 428–430 (2008).CrossRefGoogle Scholar
109.Tarun, M.C. and McCluskey, M.D.: Hydrogen-related defects in strontium titanate. J. Appl. Phys. 109, 063706:1–4 (2011).CrossRefGoogle Scholar
110.Villamagua, L., Barreto, R., Prócel, L.M., and Stashans, A.: Hydrogen impurity in SrTiO3: structure, electronic properties and migration. Phys. Scr. 75, 374–378 (2007).CrossRefGoogle Scholar
111.Bork, N., Bonanos, N., Rossmeisl, J., and Vegge, T.: Thermodynamic and kinetic properties of hydrogen defect pairs in SrTiO3 from density functional theory. Phys. Chem. Chem. Phys. 13, 15256–15263 (2011).CrossRefGoogle ScholarPubMed
112.Thienprasert, J.T., Fongkaew, I., Singh, D.J., Du, M-H., and Limpijumnong, S.: Identification of hydrogen defects in SrTiO3 by first-principles local vibration mode calculations. Phys. Rev. B. 85, 125205:1–5 (2012).CrossRefGoogle Scholar
113.Varley, J., Janotti, A., and Van de Walle, C.G.. Private communication.Google Scholar