Growth And Properties Of Pulsed Laser Deposited Al-doped ZnO Thin Film

High Power Laser Lab, Department of Physics, Indian Institute of Technology Roorkee, Roorkee-247667, Uttarakhand, India

Adv. Mater. Lett., 2015, 6 (1), pp 73-79

DOI: 10.5185/amlett.2015.5606

Publication Date (Web): Dec 28, 2014

Copyright © IAAM-VBRI Press

E-mail: physk@gmail.com

Abstract

Al-doping of 1.5% by weight, in ZnO (Al:ZnO), thin films are deposited on glass substrates at temperature 400 °C and varying oxygen gas pressure (PO₂) from 1.33 Pa to 5.32 Pa via Pulsed Laser Deposition (PLD) technique. The single crystalline nature of the thin films is confirmed from the X-ray diffraction (XRD) pattern. The evaluated crystallite size is found to be <15 nm. Atomic Force Microscopy (AFM) study reveals the columnar grain formation in the thin films, with low surface roughness. The surface morphology of the grown thin films is significantly affected by PO₂. Optical measurements depict that the thin films are highly transparent in the visible region with transmittance up to 80%. The optical band gap calculated from Tauc’s plot evinced that Al-doping results in band edge bending in Al:ZnO thin films, a red shift in the band gap is observed with increase in PO₂ that is due to the contributing electrons from oxygen ions. Photoluminescence (PL) spectra of films indicate the visible emission peaks originating from defect states. Optical properties of the thin films confirm their applicability for optoelectronic devices. The room temperature, current-voltage (I-V) plots indicate low resistivity in the thin films ~ 10^-2 (Ω-cm).

Keywords

Pulsed laser deposition, Al-doped ZnO (Al:ZnO) thin film, transmittance, Tauc&rsquo,s plot, band gap.