Journal of Materials Science

, Volume 51, Issue 19, pp 8995–9004 | Cite as

Factors limiting doping efficiency of Iridium in pulsed laser deposited TiO2 transparent conducting oxide

  • Andre SlonopasEmail author
  • Michael Melia
  • Kai Xie
  • Tatiana Globus
  • James M. Fitz-Gerald
  • Pamela Norris
Original Paper


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.


TiO2 Carrier Concentration Pulse Laser Deposition Spark Plasma Sinter TiO2 Film 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.



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.

Compliance with ethical standards

Conflict of interest

The authors declare that they have no conflict of interest.


  1. 1.
    Ellmer K (2012) Past achievements and future challenges in the development of optically transparent electrodes. Nat Photonics 6:809–817CrossRefGoogle Scholar
  2. 2.
    Kim H, Gilmore CM, Pique A, Horwitz JS, Mattoussi H, Murata H, Kafafi ZH, Chrisey DB (1999) Electrical, optical, and structural properties of indium–tin–oxide thin films for organic light-emitting devices. J Appl Phys 86:6451CrossRefGoogle Scholar
  3. 3.
    Jung D, Lee KH, Kim D, Burk D, Overzet LJ, Lee GS (2013) Highly conductive flexible multi-walled carbon nanotube sheet films for transparent touch screen. Jpn J Appl Phys 52:03BC03CrossRefGoogle Scholar
  4. 4.
    Ginley DS, Bright C (2000) Transparent conducting oxides. MRS Bull 25:15–18CrossRefGoogle Scholar
  5. 5.
    Kim H, Pique A, Horwitz JS, Murata H, Kafafi ZH, Gilmore CM, Chrisey DB (2000) Effect of aluminum doping on zinc oxide thin films grown by pulsed laser deposition for organic light-emitting devices. Thin Solid Films 377:798CrossRefGoogle Scholar
  6. 6.
    Wang JT, Shi XL, Liu WW, Zhong XH, Wang JN, Pyrah L, Sanderson KD, Ramsey PM, Hirata M, Tsuri K (2014) Influence of preferred orientation on the electrical conductivity of fluorine-doped tin oxide films. Sci Rep 4:3679Google Scholar
  7. 7.
    Latthe SS, Liu S, Terashima C, Nakata K, Fujishima A (2014) Transparent, adherent, and photocatalytic SiO2–TiO2 coatings on polycarbonate for self-cleaning applications. Coatings 4:497CrossRefGoogle Scholar
  8. 8.
    Sarah MSP, Musa MZ (2010) Electrical conductivity characteristics of TiO2 thin film. In: International conference on electronic devices, systems and applications (ICEDSA)Google Scholar
  9. 9.
    Lü X, Yang W, Quan Z, Lin T, Bai L, Wang L, Huang F, Zhao Y (2014) Enhanced electron transport in Nb-doped TiO2 nanoparticles via pressure-induced phase transitions. J Am Chem Soc 136:419–426CrossRefGoogle Scholar
  10. 10.
    Neubert M, Cornelius S, Fiedler J, Gebel T, Liepack H, Kolitsch A, Vinnichenko M (2013) Overcoming challenges to the formation of high-quality polycrystalline TiO2: Ta transparent conducting films by magnetron sputtering. J Appl Phys 114:083707CrossRefGoogle Scholar
  11. 11.
    Lozano O, Chen QY, Wadekar PV, Seo HW, Chinta PV, Chu LH, Tu LW, Lo I, Yeh SW, Ho NJ, Chuang FC, Jang DJ, Wijesundera D, Chu W-K (2013) Factors limiting the doping efficiency of transparent conductors: a case study of Nb-doped In2O3 epitaxial thin-films. Sol Energy Mater Sol Cells 113:171CrossRefGoogle Scholar
  12. 12.
    Diouf B, Jeon WS, Pode R, Kwon JH (2012) Efficiency control in iridium complex-based phosphorescent light-emitting diodes. Adv Mater Sci Eng 2012. doi: 10.1155/2012/794674
  13. 13.
    Eason R (2007) Pulsed laser deposition of thin films: applications-led growth of functional materials. Wiley, London, pp 245–247Google Scholar
  14. 14.
    Dabney MS, van Hest MFAM, Teplin CW, Arenkiel SP, Perkins JD, Ginley DS (2008) Pulsed laser deposited Nb Doped TiO2 as a transparent conducting oxide. Thin Solid Films 516:4133CrossRefGoogle Scholar
  15. 15.
    Joint Committee on Powder Diffraction Standards (1967) Powder Diffraction File. ASTM, Philadelphia, PA, Card 21-1272–PDFGoogle Scholar
  16. 16.
    Joint Committee on Powder Diffraction Standards (1967) Powder Diffraction File. ASTM, Philadelphia, PA, Card 21-1276–PDFGoogle Scholar
  17. 17.
    Joint Committee on Powder Diffraction Standards (1988) Powder Diffraction File. International Centre for Diffraction Data, Swarthmore, Pennsylvania. Card 15-870–PDFGoogle Scholar
  18. 18.
    Hitosugi T, Yamada N, Nakao S, Hirose Y, Hasegawa T (2010) Properties of TiO2-based transparent conducting oxides. Phys Status Solidi A 207:1529CrossRefGoogle Scholar
  19. 19.
    Kim H (2007) Pulsed laser deposition of thin films: applications-led growth of functional materials. Chapter 11. Transparent conducting oxide films. Wiley, London, pp 239–260Google Scholar
  20. 20.
    Perriere J, Millon E, Cracium V (2007) Pulsed laser deposition of thin films: applications-led growth of functional materials. Chapter 12. ZnO and ZnO-related compounds. Wiley, London, pp 261–289Google Scholar
  21. 21.
    Niemelä JP, Hirose Y, Hasegawa T, Karppinen M (2015) Transition in electron scattering mechanism in atomic layer deposited Nb:TiO2 thin films. Appl Phys Lett 106:042101CrossRefGoogle Scholar
  22. 22.
    Meeks T, Krieger JB (1969) Temperature dependence of the resistivity of degenerately doped semiconductors at low temperatures. Phys Rev 185:1068–1072CrossRefGoogle Scholar
  23. 23.
    Tang H, Prasad K, Sanjines R, Schmid PE, Levy F (1994) Electrical and optical properties of TiO2 anatase thin films. J Appl Phys 75:2042CrossRefGoogle Scholar
  24. 24.
    Frischbier MV, Wardenga HF, Weidner M, Bierwagen O, Jia J, Shigesato Y, Klein A (2016) Influence of dopant species and concentration on grain boundary scattering in degenerately doped In2O3 thin films. Thin Solid Films. doi: 10.1016/j.tsf.2016.03.022 Google Scholar
  25. 25.
    Yamada N, Hitosugi T, Hoang NLH, Furubayashi Y, Hirose Y, Shimada T, Hasegawa T (2007) Fabrication of low resistivity Nb-doped TiO2 transparent conductive polycrystalline films on glass by reactive sputtering. Jpn J Appl Phys 46:5275CrossRefGoogle Scholar
  26. 26.
    Jariwala D, Sangwan VK, Lauhon LJ, Marks TJ, Hersam MC (2013) Carbon nanomaterials for electronics, optoelectronics, photovoltaics, and sensing. Chem Soc Rev 42:2824–2860CrossRefGoogle Scholar
  27. 27.
    Majumdar S, Mallik R, Sampathkumaran EV, Paulose PL (1998) Residual resistivity ratio and its relation to the positive magnetoresistance behavior in natural multilayer LaMn2Ge2; relevance to artificial multilayer physics. Solid State Commun 108:349–353CrossRefGoogle Scholar
  28. 28.
    Paine DC, Whitson T, Janiac D, Beresford R, Yang CO, Lewis B (1999) A study of low temperature crystallization of amorphous thin film indium–tin–oxide. J Appl Phys 85:8445CrossRefGoogle Scholar
  29. 29.
    Lee PA, Ramakrishnan TV (1985) Disordered electronic systems. Rev Mod Phys 57:287CrossRefGoogle Scholar
  30. 30.
    Anthony PL, Arnold RG, Arroyo C, Bega K, Biesiada J, Bosted PE, Bower G, Cahoon J, Carr R, Cates GD, Chen J-P, Chudakov E, Cooke M, Decowski P, Deur A, Emam W, Erickson R, Fieguth T, Field C, Gao J, Gary M, Gustafsson K, Hicks RS, Holmes R, Hughes EW, Humensky TB, Jones GM, Kaufman LJ, Keller L, Kolomensky YuG, Kumar KS, LaViolette P, Lhuillier D, Lombard-Nelsen RM, Marshall Z, Mastromarino P, McKeown RD, Michaels R, Niedziela J, Olson M, Paschke KD, Peterson GA, Pitthan R, Relyea D, Rock SE, Saxton O, Singh J, Souder PA, Szalata ZM, Turner J, Tweedie B, Vacheret A, Walz D, Weber T, Weisend J, Woods M, Younus I (2005) Precision measurement of the weak mixing angle in Møller scattering. Phys Rev Lett 95:081601CrossRefGoogle Scholar
  31. 31.
    Kawar RK, Chigare PS, Patil PS (2003) Substrate temperature dependent structural, optical and electrical properties of spray deposited iridium oxide thin films. Appl Surf Sci 206:90CrossRefGoogle Scholar
  32. 32.
    Noh JP, Shimogishi F, Otsuka N (2003) Strong localization of carriers in δ-doped GaAs structures. Phys Rev B 67:075309CrossRefGoogle Scholar
  33. 33.
    Khan M, Gul SR, Li J, Cao W (2015) Variations in the structural, electronic and optical properties of N-doped TiO2 with increasing N doping concentration. Mod Phys Lett B 29:1550022CrossRefGoogle Scholar
  34. 34.
    Mendelsberg RJ, Garcia G, Milliron DJ (2012) Extracting reliable electronic properties from transmission spectra of indium tin oxide thin films and nanocrystal films by careful application of the drude theory. J Appl Phys 111:063515CrossRefGoogle Scholar
  35. 35.
    Sato Y, Sanno Y, Tasaki C, Oka N, Kamiyama T, Shigesato Y (2010) Electrical and optical properties of Nb-doped TiO2 films deposited by DC magnetron sputtering using slightly reduced Nb-doped TiO2-x ceramic targets. J Vac Sci Technol, A 28:851CrossRefGoogle Scholar
  36. 36.
    Kurita D, Ohta S, Sugiura K, Ohta H, Koumoto K (2006) Carrier generation and transport properties of heavily Nb-doped anatase TiO2 epitaxial films at high temperatures. J Appl Phys 100:096105CrossRefGoogle Scholar
  37. 37.
    Vlcek M, Cızek J, Prochazka I, Novotny M, Bulır J, Lancok J, Anwand W, Brauer G, Mosnier JP (2014) Defect studies of thin ZnO films prepared by pulsed laser deposition. J Phys: Conf Ser 505:012021Google Scholar
  38. 38.
    Pankove JI (1975) Optical processes in semiconductors, 2nd edn. Dover Publishers, New York, p 35Google Scholar
  39. 39.
    Valencia S, Marín JM, Restrepo G (2010) Study of the bandgap of synthesized titanium dioxide nanoparticules using the Sol–Gel method and a hydrothermal treatment. Open Mater Sci J 4:9–14Google Scholar
  40. 40.
    Enright B, Fitzmaurice D (1996) Spectroscopic determination of electron and hole effective masses in a nanocrystalline semiconductor film. J Phys Chem 100:1027–1035CrossRefGoogle Scholar
  41. 41.
    Kormann C, Bahnemann D, Hoffmann M (1988) Preparation and characterization of quantum-size titanium dioxide. J Phys Chem 92:5196CrossRefGoogle Scholar
  42. 42.
    Jain SC, McGregor JM, Roulston DJ (1990) Band-gap narrowing in novel III–V semiconductors. J Appl Phys 68:3747CrossRefGoogle Scholar
  43. 43.
    Kim CE, Moon P, Kim S, Myoung J-M, Jang HW, Bang J, Yun I (2010) Effect of carrier concentration on optical bandgap shift in ZnO: Ga thin films. Thin Solid Films 518:6304–6307CrossRefGoogle Scholar
  44. 44.
    Dunnill CW, Aiken ZA, Kafizas A, Pratten J, Wilson M, Morgan DJ, Parkin IP (2009) White light induced photocatalytic activity of sulfur-doped TiO2 thin films and their potential for antibacterial application. J Mater Chem 19:8747CrossRefGoogle Scholar
  45. 45.
    Mo Y, Stefan IC, Cai WB, Dong J, Carey P, Scherson DA (2002) In Situ Iridium LIII-Edge X-ray absorption and surface enhanced Raman spectroscopy of electrodeposited iridium oxide films in aqueous electrolytes. J Phys Chem B 106:3681–3686CrossRefGoogle Scholar
  46. 46.
    Siedle AR, Newmark RA, Brown-Wensley KA, Skarjune RP, Haddad LC, Hodgson KO, Roe AL (1988) Solid-state organometallic chemistry of molecular metal oxide clusters: carbon-hydrogen activation by an iridium polyoxometalate. Organometallics 7:2078–2079CrossRefGoogle Scholar
  47. 47.
    Hardcastle FD, Wachs IE (2005) Determination of molybdenum–oxygen bond distances and bond orders by Raman spectroscopy. J Raman Spectrosc 21:683–691CrossRefGoogle Scholar
  48. 48.
    Adonin SA, Izarova NV, Besson C, Abramov PA, Santiago-Schübel B, Kögerler P, Fedin VP, Sokolov MN (2014) An IrIV-containing polyoxometalate. Chem Commun 51:1222CrossRefGoogle Scholar
  49. 49.
    Gavartin JL, MuñozRamo D, Shluger AL, Bersuker G, Lee BH (2006) Negative oxygen vacancies in HfO2HfO2 as charge traps in high-kk stacks. Appl Phys Lett 89:082908CrossRefGoogle Scholar
  50. 50.
    Weibel A, Bouchet R, Knauth P (2006) Electrical properties and defect chemistry of anatase (TiO2). Solid State Ionics 177:229–236CrossRefGoogle Scholar

Copyright information

© Springer Science+Business Media New York 2016

Authors and Affiliations

  • Andre Slonopas
    • 1
    Email author
  • Michael Melia
    • 2
  • Kai Xie
    • 3
  • Tatiana Globus
    • 3
  • James M. Fitz-Gerald
    • 2
  • Pamela Norris
    • 1
  1. 1.Department of Mechanical and Aerospace EngineeringUniversity of VirginiaCharlottesvilleUSA
  2. 2.Department of Material Science and EngineeringUniversity of VirginiaCharlottesvilleUSA
  3. 3.Department of Electrical and Computer EngineeringUniversity of VirginiaCharlottesvilleUSA

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