Effect of Annealing Temperature on the Physical Properties of the ZnO Thin Films Deposited by Ultrasonic Spray Pyrolysis

Öz

In this work optical, electrical, structural and surface properties of polycrystalline ZnO thin films grown from aqueous solutions (with pH = 5) have been reported. The films have been deposited on glass substrates by ultrasonic spray pyrolysis technique at a substrate temperature of 350 ± 5 °C. Zinc acetate dissolved in deionized water has been used as starting solution. The ZnO thin films have been annealed in air at 450 and 500 °C to improve their physical characteristics. X-ray diffraction reveals that the films are polycrystalline in nature having zincite type crystal structure. Electrical resistivity values of the films have been increased after annealing process. Films are highly transparent in the visible region. The dependence of refractive index, n, and extinction coefficient, k, on the wavelength for ZnO films has been also reported. Optical band gap values have been determined using optical method. Finally, it has been concluded that annealing temperature has an important effect on the optical, structural, surface and electrical properties of the deposited films.

Anahtar Kelimeler

• Thin film
• Annealing
• ZnO
• X-ray diffraction
• Surface properties

Ultrasonik Kimyasal Püskürtme Yöntemiyle Elde Edilen ZnO İnce Filmlerinin Fiziksel Özellikleri Üzerine Tavlama Sıcaklığının Etkisi

Öz

Bu çalışmada, sulu çözeltilerden (pH = 5) elde edilen ZnO filmlerinin optik, elektriksel, yapısal ve yüzeysel özellikleri rapor edilmiştir. Filmler cam tabanlar üzerine 350 ± 5 °C taban sıcaklığında Ultrasonik Kimyasal Püskürtme tekniği ile çöktürülmüştür. Deiyonize su içerisinde çözünen Çinko asetat başlangıç püskürtme çözeltisi olarak kullanılmıştır. ZnO filmleri fiziksel özelliklerini iyileştirmek amacıyla 450 ve 500 °C sıcaklıklarda hava ortamında tavlama işlemine tabi tutulmuştur. X-ışını kırınımı analizleri, filmlerin polikristal formda ve zincite tipi kristal yapıya sahip olduğunu ortaya koymaktadır. Elektriksel özdirenç değerlerinin tavlama işlemi sonrasında arttığı belirlenmiştir. Filmler görünür bölgede yüksek geçirgenliğe sahiptirler. Ayrıca, filmler için kırılma indisi, n, ve sönüm katsayısının, k, dalgaboyuna bağlı değişimleri de rapor edilmiştir. Filmlerin optik bant aralığı değerleri optik metot yardımı ile belirlenmiştir. Sonuç olarak, tavlama sıcaklığının elde edilen filmlerin optik, yapısal, elektriksel ve yüzeysel özellikleri üzerinde önemli bir etkisi olduğu sonucuna varılmıştır.

Anahtar Kelimeler

• İnce film
• Tavlama
• ZnO
• X-ışını kırınımı
• Yüzey özellikleri

Kaynakça

1. Manoharan, C., Pavithra, G., Dhanapandian, S., Dhamodharan, P., 2015. Effect of In doping on the properties and antibacterial activity of ZnO films prepared by spray pyrolysis. Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 149, 793–799.
2. Lokhande, B.J., Uplane, M.D., 2000. Structural, optical and electrical studies on spray deposited highly oriented ZnO films Appl. Surf. Sci. 167, 243-246.
3. Lan, J., Kanicki J., 1996. Atomic Hydrogen Effects on the Optical and Electrical Properties of Transparent Conducting Oxides For a-Si:H TFT-LCDs. Mater. Res. Soc. Symp. 424, 347.
4. Chopra, K.L., Major, S., Panday, D.K., 1983. Transparent conductors—A status review. Thin Solid Films 102, 1-46.
5. Fortunato, E., Barquinha, P., Pimentel, A., Pereira, L., Goncalves, A., Marques, A., Martins, R., 2004. Wide-bandgap high-mobility ZnO thin-film transistors produced at room temperature. Appl. Phys. Lett. 85, 2541-2543.
6. Bretagnon, T., Lefebvre, P., Guillet, T., , Taliercio, T., and Gil, B., 2007. Barrier composition dependence of the internal electric field in ZnO/Zn1−xMgxO quantum wells. Appl. Phys. Lett. 90, 201912.
7. Amoupour, E., Ziabari, A.A., Andarva, H., Ghodsi, F.E., 2014. Influence of air/N2 treatment on the structural, morphological and optoelectronic traits of nanostructured ZnO:Mn thin films. Superlattices Microstruct. 65, 332–343.
8. Karak, N., Samantab, P.K., Kundu, T.K., 2013. Green photoluminescence from highly oriented ZnO thin film for, photovoltaic application. Optik 124 6227– 6230.

9. Benramache, S., Belahssen, O., Arif, A., Guettaf, A., 2014. A correlation for crystallite size of undoped ZnO thin film with the band gap energy–precursor molarity–substrate temperature. Optik 125, 1303– 1306.
10. Ivanova, T., Harizanova, A., Koutzarova, T., Vertruyen, B., 2014. Sol–gel nanocrystalline ZnO:Ag films: Structural and optical properties. Superlattices Microstruct. 70, 1–6.
11. Acharya, A.D., Sarwan, B., Panda, R., Shrivastava, S.B., Ganesan, V., 2014. Tuning of TCO properties of ZnO by silver addition. Superlattices Microstruct. 67, 97–109.
12. Humayun, Q,. Kashif, M., Hashim, U., 2013. ZnO thin film deposition on butterfly shaped electrodes for ultraviolet sensing applications. Optik 124, 5961– 5963.
13. Benramache, S., Benhaoua, B., 2012. Influence of annealing temperature on structural and optical properties of ZnO:In thin films prepared by ultrasonic spray technique. Superlattices Microstruct. 52, 1062–1070.
14. Nunes, P., Frenandes, B., Fortunato, E., Vilarinho, P., Martins, R., 1999. Performances presented by zinc oxide thin films deposited by spray pyrolysis. Thin Solid Films 337, 176-179.
15. Atay, F., Kose, S., Bilgin, V., Akyuz, I., 2003. CdS:Ni films obtained by ultrasonic spray pyrolysis: effect of the Ni concentration. Materials Letters 57, 3461-3472.
16. Aoun, Y., Benhaoua, B., Benramache, S., Gasmi, B. 2015. Effect of deposition rate on the structural, optical and electrical properties of Zinc oxide (ZnO) thin films prepared by spray pyrolysis technique. Optik - International Journal for Light and Electron Optics
17. Fortunato, E., Assuncao, V., Goncalves, A., Marques, A., Auas, Pereira, H.L., Ferreira, I., Martins, R., 2004. High quality conductive gallium-doped zinc oxide films deposited at room temperature. Thin Solid Films 451, 443-447.
18. Suchea, M., Christoulakis, S., Katharakis, M., Katsarakis N., Kiriakidis, G., 2005. Surface characterization of ZnO transparent thin films J. Phys.: Conf. Ser. 10 , 147–150.
19. Zhu, B.L., Xie, C.S., Zeng, D.W., Song, W.L., Wang, A.H., 2005. Investigation of gas sensitivity of Sb-doped ZnO nanoparticles. Mater. Chem. Phys. 89, 148-153.
20. Ashour, A. Kaid, M.A., El-Sayed, N.Z., Ibrahim A.A., 2006. Physical properties of ZnO thin films deposited by spray pyrolysis technique. Applied Surface Science 252, 7844–7848.
21. Wang, Y.G., Lau, S.P., Lee, H.W., Yu, S.F., Tay, B.K., Zhang, X.H., Hng, H.H., 2003. Photoluminescence study of ZnO films prepared by thermal oxidation of Zn metallic films in air. J. Appl. Phys. 4 (1) 354.
22. Mamazza, J.R., Morel, D.L., Ferekides, C.S., 2005. Transparent conducting oxide thin films of Cd2SnO4 prepared by RF magnetron co-sputtering of the constituent binary oxides. Thin Solid Films 484, 26-33.
23. Ferro, R., Rodriguez, J. A., Vigil, O., Morales-Acevedo, A., 2001. Chemical composition and electrical conduction mechanism for CdO:F thin films deposited by spray pyrolysis. Mater. Sci. Eng. B 87, 83-86.
24. Callister, W.D., 1997. Materials Science and Engineering-An Introduction, John Wiley and Sons, New York.
25. Baretta, C. and Massalaski T.B., 1966. Structure of Metals. McGraw-Hill, New York, 205 pp.
26. Khoshman, J.M.. and Kordesch, M.E., 2005. Spectroscopic ellipsometrycharacterization of amorphous aluminum nitride and indium nitride thin films, physica status solidi (c) 2 2821-2827.