Electrical and Optical Characteristics of IZO Thin Films Deposited in Different Oxygen Flow Rate

산소 유량에 따른 IZO 박막의 전기적 및 광학적 특성

  • Kwon, Su-Kyeong (Department of Materials Engineering, Korea University of Technology and Education) ;
  • Lee, Kyu-Mann (Department of Materials Engineering, Korea University of Technology and Education)
  • 권수경 (한국기술교육대학교 신소재공학과) ;
  • 이규만 (한국기술교육대학교 신소재공학과)
  • Received : 2013.12.02
  • Accepted : 2013.12.16
  • Published : 2013.12.31

Abstract

In this study, we have investigated the effect of the substrate temperature and oxygen flow rate on the characteristics of IZO thin films for the OLED (organic light emitting diodes) devices. For this purpose, IZO thin films were deposited by RF magnetron sputtering at room temperature and $300^{\circ}C$ with various $O_2$ flow rate. In order to investigate the influences of the oxygen, the flow rate of oxygen in argon mixing gas has been changed from 0.1sccm to 0.5sccm. IZO thin films deposited at room temperature show amorphous structure, whereas IZO thin films deposited at $300^{\circ}C$ show crystalline structure having an (222) preferential orientation regardless of $O_2$ flow rate. The electrical resistivity of IZO film increased with increasing flow rate of $O_2$ under Ar+$O_2$. The change of electrical resistivity with increasing flow rate of $O_2$ was mainly interpreted in terms of the charge carrier concentration rather than the charge carrier mobility. The electrical resistivity of the amorphous-IZO films deposited at R.T. was lower than that of the crystalline-IZO thin films deposited at $300^{\circ}C$. The change of electrical resistivity with increasing substrate temperature was mainly interpreted in terms of the charge carrier mobility rather than the charge carrier concentration. All the films showed the average transmittance over 85% in the visible range. The current density and the luminance of OLED devices with IZO thin films deposited at room temperature in 0.1sccm $O_2$ ambient gas are the highest amongst all other films. The optical band gap energy of IZO thin films plays a major role in OLED device performance, especially the current density and luminance.

Keywords

Acknowledgement

Supported by : 한국연구재단, 한국기술교육대학교

References

  1. K. Ishibashi, K. Hirata, and N. Hosokawa, "Mass spectrometric ion analysis in the sputtering of oxide targets," Journal of Vacuum Science & Technology A., Vol. 10, pp.1718-1722, 1992. https://doi.org/10.1116/1.577776
  2. K. Tominaga, T. Ueda, T. Ao, M. Kataoka, and I. Mori, "ITO films prepared by facing target sputtering system," Thin Solid Films, Vol. 281-282, pp. 194-197, 1996. https://doi.org/10.1016/0040-6090(96)08611-7
  3. Y. Hoshi, H. Kato, and K. Funatsu, "ITO films deposited by facing target sputtering," Thin Solid Films, Vol. 445, pp. 245-250, 2003. https://doi.org/10.1016/S0040-6090(03)01182-9
  4. N. Taga, M. Maekawa, Y. Shigesato, I. Yasui, M. Kamei and T. E. Haynes, "Deposition of Heteroepitaxial $In_2O_3$ Thin Films by Molecular Beam Epitaxy," Jpn. J. Appl.Phys., Vol. 37.6524-6529, 1998. https://doi.org/10.1143/JJAP.37.6524
  5. C. Nunes de Carvalho, A. M. Botelho do Rego, A. Amaral, P. Brogueira and G. Lavareda, "Effect of substrate temperature on the surface structure, composition and morphology of indium-tin oxide films," Surface and Coatings Technology, Vol. 124, pp. 70-75, 2000. https://doi.org/10.1016/S0257-8972(99)00619-2
  6. Y. S. Jung, J. Y. Seo, D. K. Lee and D. Y. Jeon, "Influence of DC magnetron sputtering parameters on the properties of amorphous indium zinc oxide thin film," Thin Solid Films, Vol. 445, pp. 63-71, 2003. https://doi.org/10.1016/j.tsf.2003.09.014
  7. K. H. Noh, M. K. Choi, S. H. Park, and H. R, Joo, "Amorphous Transparent Conducting film $In_2O_3:Zn$," Hankook Kwanghan Hoeji, Vol. 13, pp.455-459, 2002. https://doi.org/10.3807/KJOP.2002.13.5.455
  8. D. C. Paine, B. Yaglioglu, Z. Beiley, and S. Lee, "Amorphous IZO-based transparent thin film transistors," Thin Solid Films, Vol. 516, pp.5894-5898, 2008. https://doi.org/10.1016/j.tsf.2007.10.081
  9. L. Raniero, I. Ferreira, A. Pimentel, A. Goncalves, P. Canhola, E. Fortunato, and R. Martins, "Role of hydrogen plasma on electrical and optical properties of ZGO, ITO and IZO transparent and conductive coatings," Thin Solid Films, Vol. 511-512, pp. 295-298, 2006. https://doi.org/10.1016/j.tsf.2005.12.057
  10. R. Das, K. Adhikary, and S. Ray, "The role of oxygen and hydrogen partial pressures on structural and optical properties of ITO films deposited by reactive rfmagnetron sputtering," Appl. Surf. Sci., Vol. 253, pp. 6068 (2007). https://doi.org/10.1016/j.apsusc.2007.01.107
  11. Y. Yan, S. J. Pennycook, J. Dai, R. P. H. Chang, A. Wang, and T. J. Marks, "Polytypoid structures in annealed $In_2O_3$-ZnO films," Appl. Phys. Lett., Vol. 73, pp. 2585-2587, 1998. https://doi.org/10.1063/1.122513
  12. J. K. Lee, H. M. Kim, S. H. Park, J. J. Kim, B. R. Rhee, and S. H. Sohn, "Heat treatment effects on electrical and optical properties of ternary compound $In_2O_3$-ZnO films," J. Appl. Phys., Vol. 92, pp. 5761-5765, 2002. https://doi.org/10.1063/1.1511292
  13. H. M. Kim and J. J. kim, "Heat treatment effects on the electrical properties of $In_2O_3$-ZnO films prepared by rf-magnetron sputtering method," J. Korean Vacuum Society, Vol. 14, pp. 238-244, 2005.
  14. J. Tauc, R. Grigorovichi, and A. Vancu, "Optical Properties and Electronic Structure of Amorphous Germanium," Phys. Stat. Sol., Vol. 15, pp. 627-637, 1966. https://doi.org/10.1002/pssb.19660150224
  15. J. Jia, A. Takasaki, N. Oka, and Y. Shigesato, "Experimental observation on the Fermi level shift in polycrystalline Al-doped ZnO films," J. Appl. Phys., Vol. 112, pp. 013718-1-7, 2112. https://doi.org/10.1063/1.4733969
  16. D. H. Hwang, H. H. Ahn, K. N. Hui, K. S. Hui, and Y. G. Son, "Effect of oxygen partial pressure contents on the properties of Al-doped ZnO thin films prepared by radio frequency sputtering," J. Ceram. Proc. Res., Vol. 12, pp. 150-154, 2011.
  17. D. H. Oh, Y. S. No, S. Y. Kim, W. J. Cho, J. Y. Kim, and T. W. Kim, "Thermal effects on the structural, electrical, and optical properties of Al-doped ZnO films deposited on glass substrates," J. Ceram. Proc. Res., Vol. 12, pp. 488-491, 2011.