Influence of Beam Energy on the Properties of Pulsed Laser Deposited Al-Doped ZnO Thin Films

Abstract

The influence of beam energy on the structural, optical, and electrical properties of Al-doped ZnO (Al:ZnO) thin films deposited using the pulsed laser deposition technique is observed systematically. X-ray diffraction analysis shows the crystalline nature of the thin films with preferred orientation (0 0 2) plane and hexagonal wurtzite structures. The impact of beam energy on the lattice strain is examined by Williamson–Hall (W–H) plots. The surface morphology examined by field emission scanning electron microscopy (FESEM) and atomic force microscopy analysis show the increased aspect ratio of grains, particle density, and surface coverage with the beam energy. The elemental composition of the films depends on the beam energy. Optical properties characterized by UV-visible spectroscopy indicate high transparency over 75% in the visible region and a sharp UV absorption. The optical band gap, $E_{g}$ obtained from Tauc's plot indicates a decrease in the energy gap with an increase in laser beam energy. Burstein–Moss (B-M) shift is observed in the band gap due to Al-doping. Photoluminescence (PL) properties of the thin films indicate visible emission peaks, corresponding to deep level defects. The electrical properties analyzed by Four probe technique depict that the thin films possess a resistivity ∼10−3 Ω·cm. Al:ZnO films show good optoelectronic properties for their practical applicability in devices such as solar cells and transparent display electrodes.