ABSTRACT: Thin films (TFs) having composition ofundoped and Al-doped ZnO were deposited onto synthesized glass substrates using spray pyrolysis technique with doping concentrations of 0, 10, 15 and 20% at annealing temperature of 200oC - 400oC. The effects of the doping concentrations on the optical properties of the as-deposited films were investigated by exploiting UV-Visible spectrophotometer and Bruker profilometer to evaluate quantify surface roughness and thicknessin the spectra range of 250nm to 1200nm. The obtained results show that metallic Zn films have a preferential (011) c-axis orientation instead of the common (002) predilection. The average transmittance of the undoped film is over 90%, while the doped films have less than 70% mean transmittancein the visible region and the observed optical band gap energy increases from 3.12eV to 3.24eVwith the increase of Al doping concentrations. The lowest resistivity of 248.13Ωcm and the highest conductivity of 403.0 x 10-5(Ωcm)-1 was obtained in the film with 20% doping concentrations.
Keywords: Spray pyrolysis technique, Band gap, Al doping, ZnO TFs, UV-Vis
[1]. Jagadish, C., Pearton, S. (2006). Zinc Oxide Bulk, Thin Films and Nanostructures: Processing, Properties, and Applications, Oxford, UK: Elsevier Ltd.
[2]. Isah, K.U., Ramalan, A.M., Ahmadu, U., Ibrahim, S.O., Yabagi, J.Y., Jolayemi, B.J. (2016). Effect of Zn Film Substrate Temperature on Optical, Structural and Vibrational Characteristics of Thermally Oxidized Zn Films. Asian Journal of Applied Sciences. Vol. 9, No. 4, pp. 159-169.
[3]. Tewari, S., Bhattacharjee, A. (2010). Structural, electrical and optical studies on spray deposited Aluminium-doped ZnO thin films. Pramana-Journal of Physics, 76(1), pp. 153-163.
[4]. Fan, J., Sreekanth, K., Xie, Z., Chang, S., Rao, K. (2013). P-type ZnO materials: theory, growth, properties and devices, Prog. Mater. Sci. 58: 874-985.
[5]. Samia, T., Eiji, Y., Hideyuki, O., Keiichi, N.I. (2016). Electrical stability of Al-doped ZnO transparent electrode prepared by sol-gel method. Applied Surface Science. 377:355-360.