Skip to main content
SpringerLink
Log in

Transparent conductive SnO2 thin films via resonant Ta doping

  • Articles
  • Published:
Science China Materials Aims and scope Submit manuscript

Abstract

Transparent conductive oxide (TCO) thin films are highly desired as electrodes for modern flat-panel displays and solar cells. Alternative indium-free TCO materials are highly needed, because of the scarcity and the high price of indium. Based on the mechanism of resonant doping, Ta has been identified as an effective dopant for SnO2 to achieve highly conductive and transparent TCO. In this work, we fabricated a series of Ta-doped SnO2 thin films (Sn1−xTaxO2, x = 0.001, 0.01, 0.02, 0.03) with high conductivity and high optical transparency via a low-cost sol-gel spin coating method. The Sn0.98Ta0.02O2 film achieves the highest electrical conductivity of 855 S cm−1 with a carrier concentration of 2.3 × 1020 cm−3 and high mobility of 23 cm2 V−1 s−1. The films exhibit a very high optical transparency of 89.5% in the visible light region. High-resolution X-ray photoemission spectroscopy and optical spectroscopy were combined to gain insights into the electronic structure of the Sn1−xTaxO2 films. The optical bandgaps of the films are increased from 3.96 eV for the undoped SnO2 to 4.24 eV for the Sn0.98Ta0.02O2 film due to the occupation of the bottom of conduction band by free electrons, i.e., the Burstein-Moss effect. Interestingly, a bandgap shrinkage is also directly observed due to the bandgap renormalization arising from many-body interactions. The double guarantee of transparency and conductivity in Sn1−xTaxO2 films and the low-cost growth method provide a new platform for optoelectronic and solar cell applications.

This is a preview of subscription content, log in via an institution to check access.

Access this article

Log in via an institution

Price excludes VAT (USA)
Tax calculation will be finalised during checkout.

Instant access to the full article PDF.

Institutional subscriptions

Similar content being viewed by others

References

  1. Brunin G, Ricci F, Ha VA, et al. Transparent conducting materials discovery using high-throughput computing. npj Comput Mater, 2019, 5: 1–3

    Article  CAS  Google Scholar 

  2. Shi J, Zhang J, Yang L, et al. Wide bandgap oxide semiconductors: From materials physics to optoelectronic devices. Adv Mater, 2021, 33: 2006230

    Article  CAS  Google Scholar 

  3. Dixon SC, Scanlon DO, Carmalt CJ, et al. N-type doped transparent conducting binary oxides: An overview. J Mater Chem C, 2016, 4: 6946–6961

    Article  CAS  Google Scholar 

  4. Zhang J, Willis J, Yang Z, et al. Deep UV transparent conductive oxide thin films realized through degenerately doped wide-bandgap gallium oxide. Cell Rep Phys Sci, 2022, 3: 100801

    Article  CAS  Google Scholar 

  5. Zhang KHL, Xi K, Blamire MG, et al. P-type transparent conducting oxides. J Phys-Condens Matter, 2016, 28: 383002

    Article  Google Scholar 

  6. MarketsandMarkets. Transparent Conductive Films Market by Application and Region-Global Forecast to 2026. https://www.market-sandmarkets.com/Market-Reports/transparent-conductive-film-market-59909084.html, 2017

  7. USGS. Mineral Commodity Summaries 2021. US Geol Surv, 2021

  8. Ramarajan R, Paul Joseph D, Thangaraju K, et al. Indium-free alternative transparent conducting electrodes: An overview and recent developments. In: Rajendran S, Qin J, Gracia F, Lichtfouse E. (eds). Metal and Metal Oxides for Energy and Electronics. Environmental Chemistry for a Sustainable World. Cham: Springer, 2011, 149–183

    Google Scholar 

  9. White ME, Bierwagen O, Tsai MY, et al. Electron transport properties of antimony doped SnO2 single crystalline thin films grown by plasma-assisted molecular beam epitaxy. J Appl Phys, 2009, 106: 093704

    Article  Google Scholar 

  10. Swallow JEN, Williamson BAD, Whittles TJ, et al. Self-compensation in transparent conducting F-doped SnO2. Adv Funct Mater, 2018, 28: 1701900

    Article  Google Scholar 

  11. Toyosaki H, Kawasaki M, Tokura Y. Electrical properties of Ta-doped SnO2 thin films epitaxially grown on TiO2 substrate. Appl Phys Lett, 2008, 93: 132109

    Article  Google Scholar 

  12. Williamson BAD, Featherstone TJ, Sathasivam SS, et al. Resonant Ta doping for enhanced mobility in transparent conducting SnO2. Chem Mater, 2020, 32: 1964–1973

    Article  CAS  Google Scholar 

  13. Slassi A. Ab initio study on the structural, electronic, optical and electrical properties of Mo-, Nb- and Ta-doped rutile SnO2. Opt Quant Electron, 2016, 48: 160

    Article  Google Scholar 

  14. Tuyen LTC, Jian SR, Tien NT, et al. Nanomechanical and material properties of fluorine-doped tin oxide thin films prepared by ultrasonic spray pyrolysis: Effects of F-doping. Materials, 2019, 12: 1665

    Article  CAS  Google Scholar 

  15. Keller DA, Barad HN, Rosh-Hodesh E, et al. Can fluorine-doped tin oxide, FTO, be more like indium-doped tin oxide, ITO? Reducing FTO surface roughness by introducing additional SnO2 coating. MRS Commun, 2018, 8: 1358–1362

    Article  CAS  Google Scholar 

  16. Weidner M, Jia J, Shigesato Y, et al. Comparative study of sputter-deposited SnO2 films doped with antimony or tantalum. Phys Status Solidi B, 2016, 253: 923–928

    Article  CAS  Google Scholar 

  17. Fukumoto M, Nakao S, Shigematsu K, et al. High mobility approaching the intrinsic limit in Ta-doped SnO2 films epitaxially grown on TiO2 (001) substrates. Sci Rep, 2020, 10: 1–9

    Article  Google Scholar 

  18. Swallow JEN, Williamson BAD, Sathasivam S, et al. Resonant doping for high mobility transparent conductors: The case of Mo-doped In2O3. Mater Horiz, 2020, 7: 236–243

    Article  CAS  Google Scholar 

  19. Xu J, Liu JB, Liu BX, et al. Design of n-type transparent conducting oxides: The case of transition metal doping in In2O3. Adv Electron Mater, 2018, 4: 1700553

    Article  Google Scholar 

  20. Fortunato E, Ginley D, Hosono H, et al. Transparent conducting oxides for photovoltaics. MRS Bull, 2007, 32: 242–247

    Article  CAS  Google Scholar 

  21. Tyona MD. A theoritical study on spin coating technique. Adv Mater Res, 2013, 2: 195–208

    Article  Google Scholar 

  22. Basyooni MA, Eker YR, Yilmaz M. Structural, optical, electrical and room temperature gas sensing characterizations of spin coated multilayer cobalt-doped tin oxide thin films. Superlatt Microstruct, 2020, 140: 106465

    Article  CAS  Google Scholar 

  23. Sharma A, Tomar M, Gupta V. SnO2 thin film sensor with enhanced response for NO2 gas at lower temperatures. Sens Actuat B-Chem, 2011, 156: 743–752

    Article  CAS  Google Scholar 

  24. Niu Y, Duan L, Zhao X, et al. Effect of Sb doping on structural and photoelectric properties of SnO2 thin films. J Mater Sci-Mater Electron, 2020, 31: 3289–3302

    Article  CAS  Google Scholar 

  25. Lekshmy SNS, Anitha VSN, Thomas PKV, et al. Magnetic properties of Mn-doped SnO2 thin films prepared by the sol-gel dip coating method for dilute magnetic semiconductors. J Am Ceram Soc, 2014, 97: 3184–3191

    Article  Google Scholar 

  26. Sivakumar P, Akkera HS, Ranjeth Kumar Reddy T, et al. Influence of Ga doping on structural, optical and electrical properties of transparent conducting SnO2 thin films. Optik, 2021, 226: 165859

    Article  CAS  Google Scholar 

  27. Turgut G. Effect of Ta doping on the characteristic features of spray-coated SnO2. Thin Solid Films, 2015, 594: 56–66

    Article  CAS  Google Scholar 

  28. Stöwe K, Weber M. Niobium, tantalum, and tungsten doped tin dioxides as potential support materials for fuel cell catalyst applications. Z Anorg Allg Chem, 2020, 646: 1470–1480

    Article  Google Scholar 

  29. Cullity BD. Elements of X-ray diffraction. Reading: Addison-Wesley, 1956

    Google Scholar 

  30. Kim YW, Lee SW, Chen H. Microstructural evolution and electrical property of Ta-doped SnO2 films grown on Al2O3 (0001) by metal-organic chemical vapor deposition. Thin Solid Films, 2002, 405: 256–262

    Article  CAS  Google Scholar 

  31. He L, Luan C, Feng X, et al. UV-vis transparent conducting Ta-doped SnO2 epitaxial films grown by metal-organic chemical vapor deposition. Mater Res Bull, 2019, 118: 110488

    Article  CAS  Google Scholar 

  32. Al-Kuhaili MF. Co-sputtered tantalum-doped tin oxide thin films for transparent conducting applications. Mater Chem Phys, 2021, 257: 123749

    Article  CAS  Google Scholar 

  33. Mientus R, Weise M, Seeger S, et al. Electrical and optical properties of amorphous SnO2:Ta films, prepared by DC and RF magnetron sputtering: A systematic study of the influence of the type of the reactive gas. Coatings, 2020, 10: 204

    Article  CAS  Google Scholar 

  34. Weidner M, Brötz J, Klein A. Sputter-deposited polycrystalline tantalum-doped SnO2 layers. Thin Solid Films, 2014, 555: 173–178

    Article  CAS  Google Scholar 

  35. Muto Y, Nakatomi S, Oka N, et al. High-rate deposition of Ta-doped SnO2 films by reactive magnetron sputtering using a Sn-Ta metal-sintered target. Thin Solid Films, 2012, 520: 3746–3750

    Article  CAS  Google Scholar 

  36. Cho CJ, Pyeon JJ, Hwang CS, et al. Atomic layer deposition of Ta-doped SnO2 films with enhanced dopant distribution for thermally stable capacitor electrode applications. Appl Surf Sci, 2019, 497: 143804

    Article  CAS  Google Scholar 

  37. Nakao S, Yamada N, Hitosugi T, et al. High mobility exceeding 80 cm2 V−1 s−1 in polycrystalline Ta-doped SnO2 thin films on glass using anatase TiO2 seed layers. Appl Phys Express, 2010, 3: 031102

    Article  Google Scholar 

  38. Sun M, Liu J, Dong B. Effects of Sb doping on the structure and properties of SnO2 films. Curr Appl Phys, 2020, 20: 462–469

    Article  Google Scholar 

  39. Arun Kumar KD, Valanarasu S, Kathalingam A, et al. Nd3+ doping effect on the optical and electrical properties of SnO2 thin films prepared by nebulizer spray pyrolysis for opto-electronic application. Mater Res Bull, 2018, 101: 264–271

    Article  CAS  Google Scholar 

  40. Gupta S, Yadav BC, Dwivedi PK, et al. Microstructural, optical and electrical investigations of Sb−SnO2 thin films deposited by spray pyrolysis. Mater Res Bull, 2013, 48: 3315–3322

    Article  CAS  Google Scholar 

  41. Haacke G. New figure of merit for transparent conductors. J Appl Phys, 1976, 47: 4086–4089

    Article  CAS  Google Scholar 

  42. Ramarajan R, Purushothamreddy N, Dileep RK, et al. Large-area spray deposited Ta-doped SnO2 thin film electrode for DSSC application. Sol Energy, 2020, 211: 547–559

    Article  CAS  Google Scholar 

  43. Tauc J, Grigorovici R, Vancu A. Optical properties and electronic structure of amorphous Germanium. Phys Stat Sol (B), 1966, 15: 627–637

    Article  CAS  Google Scholar 

  44. Abdel-Galil A, Hussien MSA, Yahia IS. Low cost preparation technique for conductive and transparent Sb doped SnO2 nanocrystalline thin films for solar cell applications. Superlatt Microstruct, 2020, 147: 106697

    Article  CAS  Google Scholar 

  45. Teldja B, Noureddine B, Azzeddine B, et al. Effect of indium doping on the UV photoluminescence emission, structural, electrical and optical properties of spin-coating deposited SnO2 thin films. Optik, 2020, 209: 164586

    Article  CAS  Google Scholar 

  46. Sivakumar P, Akkera HS, Kumar Reddy TR, et al. Effect of Ti doping on structural, optical and electrical properties of SnO2 transparent conducting thin films deposited by sol-gel spin coating. Optical Mater, 2021, 113: 110845

    Article  CAS  Google Scholar 

  47. Arora I, Malhotra K, Mahajan A, et al. Structural, optical and electrical characterization of spin coated SnO2:Mn thin films. Mater Today-Proc, 2019, 36: 697–700

    Article  Google Scholar 

  48. Wang M, Gao Y, Chen Z, et al. Transparent and conductive W-doped SnO2 thin films fabricated by an aqueous solution process. Thin Solid Films, 2013, 544: 419–426

    Article  CAS  Google Scholar 

  49. Zeng LG, Liu FM, Zhong WW, et al. Preparationand structure and optical-electrical properties of the Nb/SnO2 composite thin film. Acta Phys Sin, 2011, 60: 038203

    Article  Google Scholar 

  50. Sofi AH, Shah MA, Asokan K. Structural, optical and electrical properties of ITO thin films. J Elec Materi, 2018, 47: 1344–1352

    Article  CAS  Google Scholar 

  51. Sunde TOL, Garskaite E, Otter B, et al. Transparent and conducting ITO thin films by spin coating of an aqueous precursor solution. J Mater Chem, 2012, 22: 15740–15749

    Article  CAS  Google Scholar 

  52. Koo BR, Bae JW, Ahn HJ. Low-temperature conducting performance of transparent indium tin oxide/antimony tin oxide electrodes. Ceramics Int, 2017, 43: 6124–6129

    Article  CAS  Google Scholar 

  53. Guendouz H, Bouaine A, Brihi N. Biphase effect on structural, optical, and electrical properties of Al−Sn codoped ZnO thin films deposited by sol-gel spin-coating technique. Optik, 2018, 158: 1342–1348

    Article  CAS  Google Scholar 

  54. Cai S, Li Y, Chen X, et al. Optical and electrical properties of Ta-doped ZnSnO3 transparent conducting films by sol-gel. J Mater Sci-Mater Electron, 2016, 27: 6166–6174

    Article  CAS  Google Scholar 

  55. Egdell RG, Rebane J, Walker TJ, et al. Competition between initial- and final-state effects in valence- and core-level X-ray photoemission of Sb-doped SnO2. Phys Rev B, 1999, 59: 1792–1799

    Article  CAS  Google Scholar 

  56. Kotani A, Toyozawa Y. Photoelectron spectra of core electrons in metals with an incomplete shell. J Phys Soc Jpn, 1974, 37: 912–919

    Article  CAS  Google Scholar 

  57. Borgatti F, Berger JA, Céolin D, et al. Revisiting the origin of satellites in core-level photoemission of transparent conducting oxides: The case of n-doped SnO2. Phys Rev B, 2018, 97: 155102

    Article  CAS  Google Scholar 

  58. Körber C, Krishnakumar V, Klein A, et al. Electronic structure of In2O3 and Sn-doped In2O3 by hard X-ray photoemission spectroscopy. Phys Rev B, 2010, 81: 165207

    Article  Google Scholar 

  59. Bourlange A, Payne DJ, Palgrave RG, et al. The influence of Sn doping on the growth of In2O3 on Y-stabilized ZrO2(100) by oxygen plasma assisted molecular beam epitaxy. J Appl Phys, 2009, 106: 013703

    Article  Google Scholar 

  60. Davies DW, Walsh A, Mudd JJ, et al. Identification of lone-pair surface states on indium oxide. J Phys Chem C, 2019, 123: 1700–1709

    Article  CAS  Google Scholar 

  61. Niedermeier CA, Rhode S, Ide K, et al. Electron effective mass and mobility limits in degenerate perovskite stannate BaSnO3. Phys Rev B, 2017, 95: 161202

    Article  Google Scholar 

  62. Behtash M, Joo PH, Nazir S, et al. Electronic structures and formation energies of pentavalent-ion-doped SnO2: First-principles hybrid functional calculations. J Appl Phys, 2015, 117: 175101

    Article  Google Scholar 

  63. Maleki M. Ab initio calculations of the effect of N, Nb, and Ta doping on the electronic structure and optical properties of SnO2. J Comput Electron, 2020, 19: 47–54

    Article  CAS  Google Scholar 

  64. Kílíç C, Zunger A. Origins of coexistence of conductivity and transparency in SnO2. Phys Rev Lett, 2002, 88: 095501

    Article  Google Scholar 

  65. Samson S, Fonstad CG. Defect structure and electronic donor levels in stannic oxide crystals. J Appl Phys, 1973, 44: 4618–4621

    Article  CAS  Google Scholar 

  66. Singh AK, Janotti A, Scheffler M, et al. Sources of electrical conductivity in SnO2. Phys Rev Lett, 2008, 101: 055502

    Article  Google Scholar 

  67. Ke C, Zhu W, Zhang Z, et al. Thickness-induced metal-insulator transition in Sb-doped SnO2 ultrathin films: The role of quantum confinement. Sci Rep, 2015, 5: 17424

    Article  CAS  Google Scholar 

  68. Thangaraju B. Structural and electrical studies on highly conducting spray deposited fluorine and antimony doped SnO2 thin films from SnCl2 precursor. Thin Solid Films, 2002, 402: 71–78

    Article  CAS  Google Scholar 

  69. Shanthi S, Subramanian C, Ramasamy P. Investigations on the optical properties of undoped, fluorine doped and antimony doped tin oxide films. Cryst Res Technol, 1999, 34: 1037–1046

    Article  CAS  Google Scholar 

  70. Sanon G, Rup R, Mansingh A. Band-gap narrowing and band structure in degenerate tin oxide (SnO2) films. Phys Rev B, 1991, 44: 5672–5680

    Article  CAS  Google Scholar 

  71. Walsh A, Da Silva JLF, Wei SH, et al. Nature of the band gap of In2O3 revealed by first-principles calculations and X-ray spectroscopy. Phys Rev Lett, 2008, 100: 167402

    Article  Google Scholar 

Download references

Acknowledgements

This work was supported by the National Natural Science Foundation of China (21872116 and 22075232).

Author information

Author notes

  1. These authors contributed equally to this work.

Authors and Affiliations

  1. College of Chemistry and Chemical Engineering, Xiamen University, Xiamen, 361005, China

    Vedaste Uwihoreye, Zhenni Yang, Jia-Ye Zhang, Yu-Mei Lin, Xuan Liang, Lu Yang & Kelvin H. L. Zhang

Authors
  1. Vedaste Uwihoreye
    View author publications

    You can also search for this author in PubMed Google Scholar

  2. Zhenni Yang
    View author publications

    You can also search for this author in PubMed Google Scholar

  3. Jia-Ye Zhang
    View author publications

    You can also search for this author in PubMed Google Scholar

  4. Yu-Mei Lin
    View author publications

    You can also search for this author in PubMed Google Scholar

  5. Xuan Liang
    View author publications

    You can also search for this author in PubMed Google Scholar

  6. Lu Yang
    View author publications

    You can also search for this author in PubMed Google Scholar

  7. Kelvin H. L. Zhang
    View author publications

    You can also search for this author in PubMed Google Scholar

Contributions

Uwihoreye V and Yang Z contributed to the analysis and wrote the paper; Uwihoreye V performed experiments with the support from Lin YM, Liang X and Yang L; Zhang JY performed the XPS measurements. Zhang KHL supervised the project. All authors participated in the general discussion.

Corresponding author

Correspondence to Kelvin H. L. Zhang.

Additional information

Conflict of interest

The authors declare that they have no conflict of interest.

Vedaste Uwihoreye received his master of engineering in chemical engineering from Xiamen University in 2021. His research interests center on the development of transparent and conducting oxide thin films for flat panel display and solar cell.

Kelvin H. L. Zhang is a professor at the College of Chemistry and Chemical Engineering, Xiamen University. His research interests focus on the epitaxial growth and the electronic properties of oxide semiconductor thin films relevant to optoelectronic device applications. He obtained his PhD degree in chemistry from the University of Oxford of in 2012, followed by working as a postdoc at Pacific Northwest National Laboratory and as a Herchel Smith Fellow at the University of Cambridge from 2015 to 2017.

Rights and permissions

Reprints and permissions

About this article

Check for updates. Verify currency and authenticity via CrossMark

Cite this article

Uwihoreye, V., Yang, Z., Zhang, JY. et al. Transparent conductive SnO2 thin films via resonant Ta doping. Sci. China Mater. 66, 264–271 (2023). https://doi.org/10.1007/s40843-022-2122-9

Download citation

  • Received:

  • Accepted:

  • Published:

  • Issue Date:

  • DOI: https://doi.org/10.1007/s40843-022-2122-9

Keywords

Search

Navigation