Journal of Sol-Gel Science and Technology

, Volume 77, Issue 1, pp 240–243 | Cite as

Magnetism as a tool for band-gap narrowing of zinc oxide films prepared by sol–gel method

  • Qi Shao
  • Si Qi Yao Chen
  • Oi Lam Yeung
  • Yi Shu Foo
  • Sheung Mei Ng
  • Juan Antonio Zapien
  • Chi Wah Leung
  • Antonio Ruotolo
Original Paper


spd exchange interaction was used to narrow the room-temperature band gap of zinc oxide films prepared by sol–gel method. Zinc oxide was doped with manganese ions by adding manganese chloride to the precursor and post-annealing in hydrogen. Films with different concentrations of manganese were prepared. Exchange interaction was established between the manganese ions in the lattice by introducing oxygen vacancies. The magnetic moment was found to increase with the concentration of manganese. For low concentrations of manganese, the band gap of the doped semiconductor was found to be wider than that of undoped ZnO films, in agreement with Vegard’s law. High concentrations of dopant resulted in a narrowing of the band gap. We ascribe the narrowing of the band gap to conduction band-edge Zeeman shifting.

Graphical Abstract

12 at.% Mn was successfully substituted in ZnO films deposited by sol–gel method. Exchange interaction was established between the Mn ions through the mediation of oxygen vacancies. A narrowing of the band gap of ZnO was achieved by Zeeman shifting of the bottom of the conduction band.


Diluted magnetic semiconductors Zinc oxide Band engineering 



This study was supported by the Research Grants Council of the Hong Kong Special Administrative Region, China (CityU 104512), and by the National Science Foundation of China (Grant No. 11274261).


  1. 1.
    Fujishima A, Honda K (1972) Electrochemical photolysis of water at a semiconductor electrode. Nature 238:37–38CrossRefGoogle Scholar
  2. 2.
    Gai Y, Li J, Li S-S, Xia J-B, Wei S-H (2009) Design of narrow-gap \({\rm TiO}_{2}\): a passivated codoping approach for enhanced photoelectrochemical activity. Phys Rev Lett 102:036402CrossRefGoogle Scholar
  3. 3.
    Long R, English NJ (2011) New insights into the band-gap narrowing of (n,p)-codoped TiO\(_2\) from hybrid density functional theory calculations. Chem Phys Chem 12:2604–2608Google Scholar
  4. 4.
    Wang P, Liu Z, Lin F, Zhou G, Wu J, Duan W, Gu B-L, Zhang SB (2010) Optimizing photoelectrochemical properties of TiO\(_2\) by chemical codoping. Phys Rev B 82:193103CrossRefGoogle Scholar
  5. 5.
    Zhu W, Qiu X, Iancu V, Chen X-Q, Pan H, Wang W, Dimitrijevic NM, Rajh T, Meyer HM, Paranthaman MP, Stocks GM, Weitering HH, Gu B, Eres G, Zhang Z (2009) Band gap narrowing of titanium oxide semiconductors by noncompensated anion–cation codoping for enhanced visible-light photoactivity. Phys Rev Lett 103:226401CrossRefGoogle Scholar
  6. 6.
    Chen X, Liu L, Yu PY, Mao SS (2011) Increasing solar absorption for photocatalysis with black hydrogenated titanium dioxide nanocrystals. Science 331:746–750CrossRefGoogle Scholar
  7. 7.
    Wang G, Wang H, Ling Y, Tang Y, Yang X, Fitzmorris RC, Wang C, Zhang JZ, Li Y (2011) Hydrogen-treated TiO\(_2\) nanowire arrays for photoelectrochemical water splitting. Nano Lett 11:3026–3033CrossRefGoogle Scholar
  8. 8.
    Wang H, Dou K, Teoh WY, Zhan Y, Hung TF, Zhang F, Xu J, Zhang R, Rogach AL (2013) Engineering of facets, band structure, and gas-sensing properties of hierarchical Sn\(^{2+}\)-doped SnO\(_2\) nanostructures. Adv Funct Mater 23:4847–4853Google Scholar
  9. 9.
    Diouri J, Lascaray JP, Amrani ME (1985) Effect of the magnetic order on the optical-absorption edge in \({\rm Cd}_{1-x}{\rm Mn}_{x}\)Te. Phys Rev B 31:7995–7999CrossRefGoogle Scholar
  10. 10.
    Donofrio T, Lamarche G, Woolley JC (1985) Temperature effects on the optical energy gap values of Cd\(_x\)Zn\(_y\)Mn\(_z\)Te alloys. J Appl Phys 57:1932–1936CrossRefGoogle Scholar
  11. 11.
    Bylsma RB, Becker WM, Kossut J, Debska U, Yoder-Short D (1986) Dependence of energy gap on x and T in \({\rm Zn}_{1-x}{\rm Mn}_{x}\)Se: the role of exchange interaction. Phys Rev B 33:8207–8215CrossRefGoogle Scholar
  12. 12.
    Pearton SJ, Abernathy CR, Overberg ME, Thaler GT, Norton DP, Theodoropoulou N, Hebard AF, Park YD, Ren F, Kim J, Boatner LA (2003) Wide band gap ferromagnetic semiconductors and oxides. J Appl Phys 93:1–13CrossRefGoogle Scholar
  13. 13.
    Yang H, Nie S (2009) Preparation and characterization of Co-doped ZnO nanomaterials. Mater Chem Phys 114:279–282CrossRefGoogle Scholar
  14. 14.
    Xu C, Cao L, Su G, Liu W, Qu X, Yu Y (2010) Preparation, characterization and photocatalytic activity of Co-doped ZnO powders. J Alloys Compd 497:373–376CrossRefGoogle Scholar
  15. 15.
    Wang XL, Luan CY, Shao Q, Pruna A, Leung CW, Lortz R, Zapien JA, Ruotolo A (2013) Effect of the magnetic order on the room-temperature band-gap of Mn-doped ZnO thin films. Appl Phys Lett 102:102112CrossRefGoogle Scholar
  16. 16.
    Shao Q, Ku PS, Wang XL, Cheng WF, Zapien JA, Leung CW, Borgatti F, Gambardella A, Dediu V, Ciprian R, Ruotolo A (2014) Chemical states and ferromagnetism in heavily Mn-substituted zinc oxide thin films. J Appl Phys 115:153902CrossRefGoogle Scholar
  17. 17.
    Reinhardt KA, Kern W (2008) Handbook of silicon wafer cleaning technology. William Andrew Inc., NorwichGoogle Scholar
  18. 18.
    Banerjee S, Mandal M, Gayathri N, Sardar M (2007) Enhancement of ferromagnetism upon thermal annealing in pure ZnO. Appl Phys Lett 91:182501CrossRefGoogle Scholar
  19. 19.
    Coey JMD, Venkatesan M, Fitzgerald CB (2005) Donor impurity band exchange in dilute ferromagnetic oxides. Nat Mater 4:173–179CrossRefGoogle Scholar
  20. 20.
    Egelhaaf H-J, Oelkrug D (1996) Luminescence and nonradiative deactivation of excited states involving oxygen defect centers in polycrystalline ZnO. J Cryst Growth 161:190–194CrossRefGoogle Scholar
  21. 21.
    Jin BJ, Im S, Lee S (2000) Violet and UV luminescence emitted from ZnO thin films grown on sapphire by pulsed laser deposition. Thin Solid Films 366:107–110CrossRefGoogle Scholar
  22. 22.
    Denton AR, Ashcroft NW (1991) Vegard’s law. Phys Rev A 43:3161–3164CrossRefGoogle Scholar
  23. 23.
    Kimura S-I, Ito T, Miyazaki H, Mizuno T, Iizuka T, Takahashi T (2008) Electronic inhomogeneity EuO: possibility of magnetic polaron states. Phys Rev B 78:052409CrossRefGoogle Scholar

Copyright information

© Springer Science+Business Media New York 2015

Authors and Affiliations

  • Qi Shao
    • 1
  • Si Qi Yao Chen
    • 1
  • Oi Lam Yeung
    • 1
  • Yi Shu Foo
    • 1
    • 2
  • Sheung Mei Ng
    • 3
  • Juan Antonio Zapien
    • 1
    • 2
  • Chi Wah Leung
    • 3
  • Antonio Ruotolo
    • 1
  1. 1.Department of Physics and Materials Science, Centre for Functional PhotonicsCity University of Hong KongKowloon TongHong Kong
  2. 2.Center of Super-Diamond and Advanced Films (COSDAF)City University of Hong KongKowloon TongHong Kong
  3. 3.Department of Applied Physics and Materials Research CentreHong Kong Polytechnic UniversityHung HomHong Kong

Personalised recommendations