Impact of Aluminum Oxide Content on the Structural and Optical Properties of ZnO: AlO Thin Films

Main Article Content

Hawraa Hadi Abass
Bushra A Hasan


AlO-doped ZnO nanocrystalline thin films from with nano crystallite size in the range (19-15 nm) were fabricated by pulsed laser deposition technique. The reduction of crystallite size by increasing of doping ratio shift the bandgap to IR region the optical band gap decreases in a consistent manner, from 3.21to 2.1 eV by increasing AlO doping ratio from 0 to 7wt% but then returns to grow up to 3.21 eV by a further increase the doping ratio. The bandgap increment obtained for 9% AlO dopant concentration can be clarified in terms of the Burstein–Moss effect whereas the aluminum donor atom increased the carrier's concentration which in turn shifts the Fermi level and widened the bandgap (blue-shift). The engineering of the bandgap by low concentration of AlO dopant makes ZnO: AlO thin films favorable for the fabrication of optoelectronic devices. The optical constants were calculated and was found to be greatly affected by the increasing the doping ratio.

Article Details

How to Cite
Abass HH, Hasan BA. Impact of Aluminum Oxide Content on the Structural and Optical Properties of ZnO: AlO Thin Films. IJP [Internet]. 2021 Dec. 1 [cited 2023 Sep. 26];19(51):41-53. Available from:


Kim H., Gilmore a.C., Pique A., Horwitz J., Mattoussi H., Murata H., Kafafi Z., and Chrisey D., Electrical, optical, and structural properties of indium–tin–oxide thin films for organic light-emitting devices. Journal of applied physics, 1999. 86(11) : pp. 6451-6461.

Kim H., Gilmore C., Horwitz J., Pique A., Murata H., Kushto G., Schlaf R., Kafafi Z., and Chrisey D., Transparent conducting aluminum-doped zinc oxide thin films for organic light-emitting devices. Applied Physics Letters, 2000. 76(3): pp. 259-261.

Kim H., Pique A., Horwitz J., Murata H., Kafafi Z., Gilmore C., and Chrisey D., Effect of aluminum doping on zinc oxide thin films grown by pulsed laser deposition for organic light-emitting devices. Thin solid films, 2000. 377: pp. 798-802.

Zhao J.-L., Li X.-M., Bian J.-M., Yu W.-D., and Gao X.-D., Structural, optical and electrical properties of ZnO films grown by pulsed laser deposition (PLD). Journal of Crystal Growth, 2005. 276(3-4): pp. 507-512.

Das R. and Ray S., Thickness dependence of the properties of magnetron sputtered ZnO: A1 films and its application in a-Si: H thin film solar cell. Indian Journal of Physics, 2004. 78: pp. 901-906.

He Y. and Kanicki J., High-efficiency organic polymer light-emitting heterostructure devices on flexible plastic substrates. Applied Physics Letters, 2000. 76(6): pp. 661-663.

Lee S.-H., Han S.-H., Jung H.S., Shin H., Lee J., Noh J.-H., Lee S., Cho I.-S., Lee J.-K., and Kim J., Al-doped ZnO thin film: a new transparent conducting layer for ZnO nanowire-based dye-sensitized solar cells. The Journal of Physical Chemistry C, 2010. 114(15): pp. 7185-7189.

Kaps S.r., Bhowmick S., Gröttrup J., Hrkac V., Stauffer D., Guo H., Warren O.L., Adam J., Kienle L., and Minor A.M., Piezoresistive response of quasi-one-dimensional ZnO nanowires using an in situ electromechanical device. Acs Omega, 2017. 2(6): pp. 2985-2993.

Klingshirn C., ZnO: From basics towards applications. physica status solidi, 2007. 244(9): pp. 3027-3073.

Jin X., Götz M., Wille S., Mishra Y.K., Adelung R., and Zollfrank C., A novel concept for self‐reporting materials: stress sensitive photoluminescence in ZnO tetrapod filled elastomers. Advanced Materials, 2013. 25(9): pp. 1342-1347.

Saji K.J., Tian K., Snure M., and Tiwari A., 2D tin monoxide—an unexplored p‐type van der waals semiconductor: material characteristics and field effect transistors. Advanced Electronic Materials, 2016. 2(4): pp. 1500453.

Mishra Y.K., Kaps S., Schuchardt A., Paulowicz I., Jin X., Gedamu D., Freitag S., Claus M., Wille S., and Kovalev A., Fabrication of macroscopically flexible and highly porous 3D semiconductor networks from interpenetrating nanostructures by a simple flame transport approach. Particle Systems Characterization, 2013. 9(30): pp. 775-783.

Reimer T., Paulowicz I., Röder R., Kaps S.r., Lupan O., Chemnitz S., Benecke W., Ronning C., Adelung R., and Mishra Y.K., Single step integration of ZnO nano-and microneedles in Si trenches by novel flame transport approach: whispering gallery modes and photocatalytic properties. ACS applied materials interfaces, 2014. 6(10): pp. 7806-7815.

Shukla R., Srivastava A., Srivastava A., and Dubey K., Growth of transparent conducting nanocrystalline Al doped ZnO thin films by pulsed laser deposition. Journal of crystal growth, 2006. 294(2): pp. 427-431.

Sarkar A., Ghosh S., Chaudhuri S., and Pal A., Studies on electron transport properties and the Burstein-Moss shift in indium-doped ZnO films. Thin Solid Films, 1991. 204(2): pp. 255-264.

Bhosle V., Tiwari A., and Narayan J., Electrical properties of transparent and conducting Ga doped ZnO. Journal of Applied Physics, 2006. 100(3): pp. 033713.

Sharma B.K. and Khare N., Stress-dependent band gap shift and quenching of defects in Al-doped ZnO films. Journal of Physics D: Applied Physics, 2010. 43(46): pp. 465402.

Ohyama M., Kozuka H., and Yoko T., Sol‐gel preparation of transparent and conductive aluminum‐doped zinc oxide films with highly preferential crystal orientation. Journal of the American Ceramic Society, 1998. 81(6): pp. 1622-1632.

Lee J.-H. and Park B.-O., Transparent conducting ZnO: Al, In and Sn thin films deposited by the sol–gel method. Thin solid films, 2003. 426(1-2): pp. 94-99.

Yamamoto Y., Saito K., Takahashi K., and Konagai M., Preparation of boron-doped ZnO thin films by photo-atomic layer deposition. Solar energy materials solar cells, 2001. 65(1-4): pp. 125-132.

Sanchez-Juarez A., Tiburcio-Silver A., Ortiz A., Zironi E., and Rickards J., Electrical and optical properties of fluorine-doped ZnO thin films prepared by spray pyrolysis. Thin Solid Films, 1998. 333(1-2): pp. 196-202.

Natsume Y. and Sakata H., Electrical and optical properties of zinc oxide films post-annealed in H2 after fabrication by sol–gel process. Materials Chemistry Physics, 2003. 78(1): pp. 170-176.

Zhan Z., Zhang J., Zheng Q., Pan D., Huang J., Huang F., and Lin Z., Strategy for preparing Al-doped ZnO thin film with high mobility and high stability. Crystal growth design, 2011. 11(1): pp. 21-25.

Mishra D., Srivastava A., Srivastava A., and Shukla R., Bead structured nanocrystalline ZnO thin films: synthesis and LPG sensing properties. Applied Surface Science, 2008. 255(5): pp. 2947-2950.

Das A., Misra P., Bose A., Joshi S., Kumar R., Sharma T., and Kukreja L., Structural, electrical and optical characteristics of Al doped ZnO films grown by sequential pulsed laser deposition. Phys. Express, 2013. 3(5).

26.Lu J., Fujita S., Kawaharamura T., Nishinaka H., Kamada Y., Ohshima T., Ye Z., Zeng Y., Zhang Y., and Zhu L., Carrier concentration dependence of band gap shift in n-type ZnO: Al films. Journal of Applied Physics, 2007. 101(8): pp. 083705.

27. Misra K.P., Shukla R., Srivastava A., and Srivastava A., Blueshift in optical band gap in nanocrystalline Zn 1− x Ca x O films deposited by sol-gel method. Applied Physics Letters, 2009. 95(3): pp. 031901.

Das A., Misra P., and Kukreja L., Effect of Si doping on electrical and optical properties of ZnO thin films grown by sequential pulsed laser deposition. Journal of Physics D: Applied Physics, 2009. 42(16): pp. 165405.

Yadav H.K. and Gupta V., A comparative study of ultraviolet photoconductivity relaxation in zinc oxide (ZnO) thin films deposited by different techniques. Journal of Applied Physics, 2012. 111(10): pp. 102809.

Wu K.-Y., Wang C.-C., and Chen D.-H., Preparation and conductivity enhancement of Al-doped zinc oxide thin films containing trace Ag nanoparticles by the sol–gel process. Nanotechnology, 2007. 18(30): pp. 305604.

Srivastava A., Kumar N., and Khare S., Enhancement in UV emission and band gap by Fe doping in ZnO thin films. Opto-Electronics Review, 2014. 22(1): pp. 68-76.

Cullity B. and Stock S., Elements of X-ray Diffraction, 3rd edn. Prentice Hall. New York, 2001: pp. 174-177.

Srivastava A., Kumar N., Misra K.P., and Khare S., Blue-light luminescence enhancement and increased band gap from calcium-doped zinc oxide nanoparticle films. Materials science in semiconductor processing, 2014. 26: pp. 259-266.

Lee J.-H. and Park B.-O., Characteristics of Al-doped ZnO thin films obtained by ultrasonic spray pyrolysis: effects of Al doping and an annealing treatment. Materials Science Engineering: B, 2004. 106(3): pp. 242-245.

Zhou H.-m., Yi D.-q., Yu Z.-m., Xiao L.-r., and Li J., Preparation of aluminum doped zinc oxide films and the study of their microstructure, electrical and optical properties. Thin solid films, 2007. 515(17): pp. 6909-6914.

Chen K.-J., Fang T.-H., Hung F.-Y., Ji L.-W., Chang S.-J., Young S.-J., and Hsiao Y., The crystallization and physical properties of Al-doped ZnO nanoparticles. Applied surface science, 2008. 254(18): pp. 5791-5795.

Venkatachalam S., Iida Y., and Kanno Y., Preparation and characterization of Al doped ZnO thin films by PLD. Superlattices Microstructures, 2008. 44(1): pp. 127-135.

Chabane L., Zebbar N., Kechouane M., Aida M., and Trari M., Al-doped and in-doped ZnO thin films in heterojunctions with silicon. Thin Solid Films, 2016. 605: pp. 57-63.

Tauc J., Optical Properties of Solids, ed. F. Abeles, NorthHolland, Amsterdam, 1970. 22: pp. 903.

Mia M., Habiba U., Pervez M., Kabir H., Nur S., Hossen M., Sen S., Hossain M.K., Iftekhar M.A., and Rahman M.M., Investigation of aluminum doping on structural and optical characteristics of sol–gel assisted spin-coated nano-structured zinc oxide thin films. Applied Physics A, 2020. 126(3): pp. 1-12.

Kumar J. and Kumar Srivastava A., Band gap narrowing in zinc oxide-based semiconductor thin films. Journal of Applied Physics, 2014. 115(13): pp. 134904.

Saw K., Aznan N., Yam F., Ng S., and Pung S., New insights on the burstein-moss shift and band gap narrowing in indium-doped zinc oxide thin films. PloS one, 2015.10(10): pp. e0141180.

Wang J., Wang Z., Huang B., Ma Y., Liu Y., Qin X., Zhang X., and Dai Y., Oxygen vacancy induced band-gap narrowing and enhanced visible light photocatalytic activity of ZnO. ACS applied materials interfaces, 2012. 4(8): pp. 4024-4030.

Bylsma R., Becker W., Kossut J., Debska U., and Yoder-Short D., Dependence of energy gap on x and T in Zn 1− x Mn x Se: the role of exchange interaction. Physical Review B, 1986. 33(12): pp. 8207.

Fukumura T., Jin Z., Ohtomo A., Koinuma H., and Kawasaki M., An oxide-diluted magnetic semiconductor: Mn-doped ZnO. Applied physics letters, 1999. 75(21): pp. 3366-3368.

Furdyna J.K., Diluted magnetic semiconductors. Journal of Applied Physics, 1988. 64(4): pp. R29-R64.

Pankove J.I., Optical processes in semiconductors. 1975: Dover Publications, Inc., New York.

Fentahun D.A., Tyagi A., and Kar K.K., Numerically investigating the AZO/Cu2O heterojunction solar cell using ZnO/CdS buffer layer. Optik, 2021. 228: pp. 166228.