Abstract
Background: Al-doped ZnO thin films are considered as a promising alternative to ITO in optoelectronic applications. In this work, Al-doped ZnO thin films were prepared using sol-gel spin coating technique.
Experimental: The optical properties of the films such as refractive index, extinction coefficient, dielectric function and the absorption coefficient were examined using spectroscopic ellipsometry method in the wavelength range of 300 to 900 nm. The effect of Al doping on ZnO thin films with different Al concentrations was significant. Tauc relation was used to estimate the optical band gap energy of the films.
Results: The calculated values of band gap energy were obtained between 3.10 to 3.25 eV. Also the fraction of voids was calculated using Aspnes theory.
Conclusion: The free carrier concentration value was obtained in the order of 1019 cm-3.
Keywords: Al doping, spectroscopic ellipsometry, ZnO thin film, band gap energy, semiconductors, polarization state.
Graphical Abstract
[1]
Tabassum, S.; Yamasue, E.; Okumura, H.; Ishihara, K.N. Electrical stability of Al-doped ZnO transparent electrode prepared bysol-gel method. Appl. Surf. Sci., 2016, 377, 355-360.
[2]
Srinatha, N.; Raghu, P.; Mahesh, H.M.; Angadi, B. Spin-coated Al-doped ZnO thin films for optical applications: Structural, micro-structural, optical and luminescence studies. J. Alloys Compd., 2017, 722, 888-895.
[3]
Gençyılmaz, O.; Atay, F.; Akyüz, I. Deposition and ellipsometric characterization of transparent conductive Al-doped ZnO for solar cell application. J. Clean Energy Technol, 2016, 4, 90-94.
[4]
Yu, X.; Yu, X.; Zhang, J.; Zhang, D.; Chen, L.; Long, Y. Light-trapping Al-doped ZnO thin films for organic solar cells. Sol. Energy, 2017, 153, 96-103.
[5]
Musat, V.; Rego, A.M.R.; Monteiro, R.; Fortunato, E. Microstructure and gas-sensing properties of sol–gel ZnO thin films. Thin Solid Films, 2008, 516, 1512-1515.
[6]
Lee, H.; Zhang, X.; Hwang, J.; Park, J. Morphological influence of solution-processed zinc oxide films on electrical characteristics of thin-film transistors. Materials, 2016, 9, 851.
[7]
Kumar, M.; Jeong, H.; Lee, D. Sol-gel derived Hf- and Mg-doped high-performance ZnO thin film transistors. J. Alloys Compdounds, 2017, 720, 230.
[8]
Ng, Z-N.; Chan, K-Y.; Low, C-Y.; Kamaruddin, S.A.; Sahdan, M.Z. Al and Ga doped ZnO films prepared by a sol–gel spin coating technique. Ceramics. Int., 2015, 41, 254.
[9]
Jain, A.; Johari, M.; Jain, A.; Pandey, P.K.; Agrawa, R. Modification in optical properties of ZnO thin film by annealing. Int. J. Innovat. Res. Sci. Eng. Technol., 2013, 2, 3144-3148.
[10]
Choi, S.Y.; Choi, K.; Kim, S.J. Rapid thermal annealing effects on the electrical and structural properties of the AZO thin film deposited at a room temperature. Int. J. Adv. Res. Electrical Electron. Instrument. Eng, 2013, 2, 6034-6043.
[11]
Bhardwaj, V.; Chowdhury, R.; Jayaganthan, R. Research articleAbstract only nanomechanical and microstructural characterization of sputter deposited ZnO thin films. Appl. Surf. Sci., 2016, 389, 1023-1032.
[12]
Alami, Z.Y.; Salem, M.; Gaidi, M.; Elkhamkhami, J. Effect of Zn concentration on structural and optical proprieties of ZnO thin films deposited by spray pyrolysis. Adv. Energy, 2015, 2, 11-24.
[13]
Moreh, A.U.; Momoh, M.; Abdullahi, S.; Shehu, J.S.; Mustapha, M.O.; Martha, N.C. The role of annealing temperature on optical properties of ZnO thin films prepared by spray pyrolysis techniques. J. Multidisciplin. Eng. Sci. Technol, 2015, 2, 2247-2251.
[14]
Juwhari, H.K.; Ikhmayies, H.K.; Lahlouh, B. Room temperature photoluminescence of spraydeposited ZnO thin films on glass substrates. Int. J. Hydrogen Energy, 2017, 42, 1-7.
[15]
Vallejos, S.; Maggio, F.D.; Shujah, T.; Blackman, C. Chemical vapour deposition of gas sensitive metal oxides. Chemosensors , 2016, 4, 1-18.
[16]
Ivanova, T.; Harizanova, A.; Koutzarova, T.; Vertruyen, B. Optical characterization of sol–gel ZnO:Al thin films. Superlatt Microstruct., 2015, 85, 101-111.
[17]
Duan, L.; Zhao, X.; Zhang, Y.; Shen, H.; Liu, R. Fabrication of flexible Al-doped ZnO films via sol–gel method. Mater. Lett., 2016, 162, 199-202.
[18]
Mahdavi, R.; Talesh, S.A. Sol-gel synthesis, structural and enhanced photocatalytic performance of Al doped ZnO nanoparticles. Adv. Powder Technol., 2017, 28, 1418-1425.
[19]
Chaitra, U.; Kekuda, D.; Rao, K.M. Effect of annealing temperature on the evolution of structural, microstructural, and optical properties of spin coated ZnO thin films. Ceram. Int., 2017, 43, 7115-7122.
[20]
Sandeep, K.M.; Bhat, S.; Dharmaprakash, S.M. Structural, optical, and LED characteristics of ZnO and Al doped ZnO thin films. J. Phys. Chem. Solids, 2017, 104, 36-44.
[21]
Verma, K.; Chaudhary, B.; Kumar, V.; Sharma, V.; Kumar, M. Influence of Fe-doping on the structural, optical and luminescent behavior of ZnO thin films deposited by spin coating technique. Vacuum, 2017, 146, 478-482.
[22]
Aghgonbad, M.M.; Sedghi, H. Optical and electronic analysis of pure and Fe-doped ZnO thin films using spectroscopic ellipsometry and Kramers-Kronig method. Int. J. Nanosci., 2018, 17, 1850013
[23]
Aghgonbad, M.M.; Sedghi, H. Spectroscopic Ellipsometry studies on zinc oxide thin films deposited by sol-gel method with various precursor concentrations. Surf. Rev. Lett., 2018., 1850158
[24]
Aghgonbad, M.M.; Sedghi, H. Influence of annealing temperature on optical properties of zinc oxide thin films analyzed by spectroscopic ellipsometry method. Chinese J. Phys., 2018, 56, 2129-2138.
[25]
Aghgonbad, M.M.; Sedghi, H. Spectroscopic- ellipsometry measurement of the optical properties of zinc oxide thin films prepared by sol-gel method: Coating speed effect. Micro & Nano Lett., 2018, 13, 959-964.
[26]
Peters, S. Spectra ray and application tutorial. In: Spectroscopic ellipsometry- theory and application; J.A. Woollam: USA, 2009.
[27]
Leng, J.; Opsal, J.; Chu, H.; Senko, M.; Aspnes, D.E. Analytic representations of the dielectric functions of materials for device and structural modeling. Thin Solid Films, 1998, 313-314, 132-136.
[28]
Soylu, M.; Coskun, M. controlling the properties of ZnO thin films by varying precursor concentration. J. Alloys Compd., 2018, 741, 957-968.
[29]
Rajendra, B.V.; Bhat, V.; Kekuda, D. influence of processing parameters on the optical properties of zinc oxide thin films grown by spray pyrolysis. Int. J. Emerg. Technol. Adv. Eng., 2013, 3, 82-85.
[30]
Chahmat, N.; Haddad, A.; Ain-Souya, A.; Ganfoudi, R.; Attaf, N.; Aida, M.S.; Ghers, M. Effect of Sn doping on the properties of ZnO thin films prepared by spray pyrolysis. J. Modern. Phys., 2012, 3, 1781-1785.
[31]
Mathew, J.P.; Varghese, G.; Mathew, J. Effect of post-thermal annealing on the structural and optical properties of ZnO thin films prepared from a polymer precursor. Chin. Phys. B, 2012, 21, 078104
[32]
Mahroug, A.; Boudjadar, S.; Hamrit, S.; Guerbous, L. Structural, optical and photocurrent properties of undoped and Al-doped ZnO thin films deposited by sol–gel spin coating technique. Mater. Lett., 2014, 134, 248-251.
[33]
Aspnes, E.; Kinsbron, E.; Bacon, D.D. Optical properties of Au: Sample effects. Phys. Rev., 1980, 21, 3290.
[34]
Spitzer, W.G.; Fan, H.Y. Determination of optical constants and carrier effective mass of semiconductors. Phys. Rev., 1957, 106, 882.
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