In the present study, a sol-gel dip-coating process was used to deposit almost stress free highly c-axis oriented nanostructured ZnO thin films on glass substrates. The effects of low silver doping concentration (Ag ? 1 at.%) on the structural, morphological and optical properties of such films were investigated using different characterization techniques. X-ray diffraction (XRD) measurements have revealed that all the ?lms were single phase and had a hexagonal wurtzite structure. The grain size values were calculated and found to be about 24-29 nm. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) images have shown that film morphology and surface roughness were influenced by Ag doping concentration. Optical properties such as transmittance and optical bandgap energy (Eg) were examined using UV-Visible spectrophotometry. The results have indicated that all the prepared ?lms were highly transparent with average visible transmission values ranging from 80% to 86%. Moreover, it was found that the Ag contents leads to widening of the bandgap.
This study is one of very few studies which have investigated the preparation of low Ag-doped ZnO thin films by the sol-gel dip-coating technique. It was put into evidence that incorporation of low Ag concentrations (Ag ? 1 at.%) in ZnO can indeed improve its physical properties.
R. E. Marotti, P. Giorgi, G. Machado, and E. A. Dalchiele, "Crystallite size dependence of band gap energy for electrodeposited ZnO grown at different temperatures," Solar Energy Materials and Solar Cells, vol. 90, pp. 2356–2361, 2006.
K. Qiu, Y. Zhao, Y. Gao, X. Liu, X. Ji, S. Cao, J. Tang, Y. Sun, D. Zhang, B. Feng, and X. Xu, "Refractive index of a single ZnO microwire at high temperatures," Applied Physics Letters, vol. 104, p. 081109, 2014.
W. Liu, K. Wang, H. Long, S. Chu, B. Wang, and P. Lu, "Near-resonant second-order nonlinear susceptibility in c-axis oriented ZnO nanorods," Applied Physics Letters, vol. 105, p. 071906, 2014.
L. Béaur, T. Bretagnon, B. Gil, A. Kavokin, T. Guillet, C. Brimont, D. Tainoff, M. Teisseire, and J. M. Chauveau, "Exciton radiative properties in nonpolar homoepitaxial ZnO/ (Zn,Mg) O quantum wells," Physical Review B, vol. 84, p. 165312, 2011.
K. L. Chopra, S. Major, and D. K. Pandya, "Transparent conductors-A status review," Thin Solid Films, vol. 102, pp. 1–46, 1983.
G. M. Nam and M. S. Kwon, "Transparent conducting Ga-doped ZnO thin films for flat-panel displays with a sol-gel spin coating," Journal of Information Display, vol. 9, pp. 8–11, 2008.
S. Major and K. L. Chopra, "Indium-doped zinc oxide films transparent electrodes for solar cells," Solar Energy Materials and Solar Cells, vol. 17, pp. 319–327, 1988.
C. L. Jia, K. M. Wang, X. L. Wang, X. J. Zhang, and F. Lu, "Formation of c-axis oriented ZnO optical waveguides by radio-frequency magnetron sputtering," Optics Express, vol. 13, pp. 5093–5099, 2005.
W. Peng, Y. He, X. Zhao, H. Liu, X. Kang, and C. Wen, "Study on the performance of ZnO nanomaterial-based surface acoustic wave ultraviolet detectors," Journal of Micromechanics and Microengineering, vol. 23, p. 125008, 2013.
M. Zam?rescu, A. Kavokin, B. Gil, G. Malpuech, and M. Kaliteevski, "ZnO as a material mostly adapted for the realization of room temperature polariton lasers," Physical Review B, vol. 65, p. 161205, 2002.
M. Karyaoui, A. Mhamdi, H. Kaouach, A. Labidi, A. Boukhachem, K. Boubaker, M. Amlouk, and R. Chtourou, "Some physical investigations on silver-doped ZnO sprayed thin films," Materials Science in Semiconductor Processing, vol. 30, pp. 255–262, 2015.
I. S. Kim, E. K. Jeong, D. Y. Kim, M. Kumar, and S. Y. Choi, "Investigation of p-type behavior in Ag-doped ZnO thin films by E-beam evaporation," Applied Surface Science, vol. 55, pp. 4011–4014, 2009.
L. N. Wang, L. Z. Hu, H. Q. Zhang, Y. Qiu, Y. Lang, G. Q. Liu, J. Y. Ji, J. X. Ma, and Z. W. Zhao, "Studying the Raman spectra of Ag doped ZnO films grown by PLD," Materials Science in Semiconductor Processing, vol. 14, pp. 274–277, 2011.
T. M. Barnes, J. Leaf, C. Fry, and C. A. Wolden, "Room temperature chemical vapour deposition of c-axis ZnO," Journal of Crystal Growth, vol. 274, pp. 412–417, 2005.
J. B. Lee, C. K. Park, and J. S. Park, "Physical properties of RF-sputtered ZnO thin films: Effects of two-step deposition," Journal of the Korean Physical Society, vol. 50, pp. 1073–1078, 2007.
M. A. Vasquez-A, O. Goiz, R. Baca-Arroyo, J. A. Andraca-Adame, G. Romero-Paredes, and R. Peña-Sierra, "Study of the properties of ZnO: Zn thin films obtained from ZnO/Zn/ZnO structure deposited by DC sputtering," Journal of Nanoscience and Nanotechnology, vol. 12, pp. 9234–9237, 2012.
J. Xu, Z. Y. Zhang, Y. Zhang, B. X. Lin, and Z. X. Fu, "Effect of Ag doping on optical and electrical properties of ZnO thin films," Chinese Physics Letters, vol. 22, pp. 2031–2034, 2005.
L. Xu, G. Zheng, L. Zhao, and S. Pei, "Two different mechanisms on UV emission enhancement in Ag-doped ZnO thin ?lms," Journal of Luminescence, vol. 158, pp. 396–400, 2015.
S. W. Shin, I. Y. Kim, K. S. Jeon, J. Y. Heo, G. S. Heo, P. S. Patil, J. H. Kim, and J. Y. Lee, "Wide band gap characteristic of quaternary and flexible Mg and Ga co-doped ZnO transparent conductive thin films," Journal of Asian Ceramic Societies, vol. 1, pp. 262–266, 2013.
K. C. Kim, E. K. Kim, and Y. S. Kim, "Growth and physical properties of sol–gel derived co doped ZnO thin film," Superlattices and Microstructures, vol. 42, pp. 246–250, 2007.
A. N. Gruzintsev, V. T. Volkov, and E. E. Yakimov, "Photoelectric properties of ZnO films doped with Cu and Ag acceptor impurities," Semiconductors, vol. 37, pp. 259–262, 2003.
H. S. Kang, B. D. Ahn, J. H. Kim, G. H. Kim, S. H. Lim, H. W. Chang, and S. Y. Lee, "Structural, electrical, and optical properties of p-type ZnO thin films with Ag dopant," Applied Physics Letters, vol. 88, pp. 202108-202113, 2006.
M. Liu, S. W. Qu, W. W. Yu, S. Y. Bao, C. Y. Ma, Q. Y. Zhang, J. He, J. C. Jiang, E. I. Meletis, and C. L. Chen, "Photoluminescence and extinction enhancement from ZnO films embedded with Ag nanoparticles," Applied Physics Letters, vol. 97, p. 231906, 2010.
E. K. Jeong, I. S. Kim, D. H. Kim, and S. Y. Choi, "Effect of deposition and annealing temperature on structural, electrical and optical properties of Ag doped ZnO thin films," Korean Journal of Materials Research, vol. 18, pp. 84–91, 2008.
L. Duan, W. Gao, R. Chen, and Z. Fu, "Influence of post-annealing conditions on properties of ZnO: Ag films," Solid State Communications, vol. 145, pp. 479–481, 2008.
H. Xue, X. L. Xu, Y. Chen, G. H. Zhang, and S. Y. Ma, "Influence of Ag-doping on the optical properties of ZnO films," Applied Surface Science, vol. 255, pp. 1806–1810, 2008.
K. Liu, B. Yang, H. Yan, Z. Fu, M. Wen, Y. Chen, and J. Zuo, "Strong room-temperature ultraviolet emission from nanocrystalline ZnO and ZnO: Ag films grown by ultrasonic spray pyrolysis," Applied Surface Science, vol. 255, pp. 2052–2056, 2008.
Y. Chen, X. L. Xu, G. H. Zhang, H. Xue, and S. Y. Ma, "A comparative study of the microstructures and optical properties of Cu-and Ag-doped ZnO thin films," Physica B: Condensed Matter, vol. 404, pp. 3645–3649, 2009.
D. R. Sahu, "Studies on the properties of sputter-deposited Ag-doped ZnO films," Microelectronics Journal, vol. 38, pp. 1252–1256, 2007.
F. Xian, K. Miao, X. Bai, Y. Ji, F. Chen, and X. Li, "Characteraction of Ag-doped ZnO thin film synthesized by sol-gel method and its using in thin film solar cells," Optik - International Journal for Light and Electron Optics, vol. 124, pp. 4876– 4879, 2013.
X. D. Zhou, X. H. Xiao, J. X. Xu, G. X. Cai, F. Ren, and C. Z. Jiang, "Mechanism of the enhancement and quenching of ZnO photoluminescence by ZnO-Ag coupling," Europhysics Letter, vol. 93, p. 57009, 2011.
M. K. Puchert, P. Y. Timbrell, and R. N. Lamb, "Postdeposition annealing of radio frequency magnetron sputtered ZnO films," Journal of Vacuum Science & Technology A, vol. 14, pp. 2220–2230, 1996.
M. Chen, Z. L. Pei, C. Sun, L. S. Wen, and X. Wang, "Surface characterization of transparent conductive oxide al-doped ZnO films," Journal of Crystal Growth, vol. 220, pp. 254–262, 1996.
J. I. Langford and A. J. C. Wilson, "Scherrer after sixty years: A survey and some new results in the determination of crystallite size," Journal of Applied Crystallography, vol. 11, pp. 102-113, 1978.
S. T. Kuo, W. H. Tuan, J. Shieh, and S. F. Wang, "Effect of Ag on the microstructure and electrical properties of ZnO," Journal of the European Ceramic Society, vol. 27, pp. 4521–4527, 2007.
A. Sanchez-Juarez, A. Tiburcio-Silver, A. Ortiz, E. P. Zironi, and J. Rickards, "Electrical and optical properties of fluorine-doped ZnO thin films prepared by spray pyrolysis," Thin Solid Films, vol. 333, pp. 196–202, 1998.
N. Volbers, H. Zhou, C. Knies, D. Pfisterer, J. Sann, D. M. Hofmann, and B. K. Meyer, "Synthesis and characterization of ZnO: Co2+ nanoparticles," Applied Physics A, vol. 88, pp. 153–155, 2007.
L. Li, W. Wang, H. Liu, X. Liu, Q. Song, and S. Ren, "First principles calculations of electronic band structure and optical properties of Cr-doped ZnO," Journal of Physical Chemistry C, vol. 113, pp. 8460–8464, 2009.
D. Ne?as and P. Klapetek, "Gwyddion: An open-source software for SPM data analysis," Central European Journal of Physics, vol. 10, pp. 181–188, 2012.
M. Wang, E. J. Kim, S. Kim, J. S. Chung, I. Yoo, E. W. Hahn, S. H. Shin, and C. Park, "Optical and structural properties of sol–gel prepared Mg ZnO alloy thin ?lms," Thin Solid Films, vol. 516, pp. 1124–1129, 2008.
M. C. Jun and J. H. Koh, "Effects of NIR annealing on the characteristics of al-doped ZnO thin films prepared by RF sputtering," Nanoscale Research Letters, vol. 7, pp. 294-297, 2012.
S. H. Jeong, B. N. Park, S. B. Lee, and J. H. Bo, "Metal-doped ZnO thin films: Synthesis and characterizations," Surface and Coatings Technology, vol. 201, pp. 5318–5322, 2007.
E. Burstein, "Anomalous optical absorption limit in inSb," Physical Review, vol. 93, pp. 632–633, 1954.
T. S. Moss, "The interpretation of the properties of indium antimonide," Proceedings of the Physical Society of London B, vol. 67, pp. 775–782, 1954.