Highly conductive and transparent laser ablated nanostructured Al: ZnO thin films

• DOI: 10.1016/j.apsusc.2010.07.044
• Publication Date: 2010-07-23T08:41:23Z
• Authors: R. Vinodkumar; I. Navas; S.R. Chalana; K.G. Gopchandran; V. Ganesan; Reji Philip; S.K. Sudheer; V.P. Mahadevan Pi...
• Keywords: Wurtzite crystal structure; Pulsed Laser Deposition; Nanocrystalline material

Abstract Al doped ZnO thin films are prepared by pulsed laser deposition on quartz substrate at substrate temperature 873 K under a background oxygen pressure of 0.02 mbar. The films are systematically analyzed using X-ray diffraction, atomic force microscopy, micro-Raman spectroscopy, UV–vis spectroscopy, photoluminescence spectroscopy, z -scan and temperature-dependent electrical resistivity measurements in the temperature range 70–300 K. XRD patterns show that all the films are well crystallized with hexagonal wurtzite structure with preferred orientation along (0 0 2) plane. Particle size calculations based on XRD analysis show that all the films are nanocrystalline in nature with the size of the quantum dots ranging from 8 to 17 nm. The presence of high frequency E 2 mode and longitudinal optical A 1 (LO) modes in the Raman spectra suggest a hexagonal wurtzite structure for the films. AFM analysis reveals the agglomerated growth mode in the doped films and it reduces the nucleation barrier of ZnO by Al doping. The 1% Al doped ZnO film presents high transmittance of ∼75% in the visible and near infrared region and low dc electrical resistivity of 5.94 × 10 −6 Ω m. PL spectra show emissions corresponding to the near band edge (NBE) ultra violet emission and deep level emission in the visible region. Nonlinear optical measurements using the z -scan technique shows optical limiting behavior for the 5% Al doped ZnO film.