Pulsed laser deposited Al-doped ZnO thin films for optical applications

Highly transparent and conducting Al-doped Zn O(Al:Zn O) thin films were grown on glass substrates using pulsed laser deposition technique.The profound effect of film thickness on the structural, optical and electrical properties of Al:Zn O thin films was observed. The X-ray diffraction depicts c-axis, plane(002) oriented thin films with hexagonal wurtzite crystal structure. Al-doping in Zn O introduces a compressive stress in the films which increase with the film thickness. AFM images reveal the columnar grain formation with low surface roughness. The versatile optical properties of Al:Zn O thin films are important for applications such as transparent electromagnetic interference(EMI) shielding materials and solar cells. The obtained optical band gap(3.2–3.08 e V) was found to be less than pure Zn O(3.37 e V) films. The lowering in the band gap in Al:Zn O thin films could be attributed to band edge bending phenomena. The photoluminescence spectra gives sharp visible emission peaks, enables Al:Zn O thin films for light emitting devices(LEDs) applications. The current–voltage(I–V) measurements show the ohmic behavior of the films with resistivity(ρ) 10-3Ω cm.