Investigation of structural and optical properties of ZnO thin films of different thickness grown by pulsed laser deposition method

In this paper, we investigated the effect of film thickness on structural, surface morphology and optical properties of ZnO thin films grown by pulsed laser deposition (PLD) method. Thickness of the films was varied by keeping all other PLD parameters same to investigate thickness dependence on the structural and optical properties of ZnO thin films. The prepared thin films have been characterized by X-ray diffraction (XRD), atomic force microscopy (AFM), UV- visible (Uv-Vis) and photoluminescence (PL) spectroscopy. XRD confirms the formation of crystalline c-axis orientated hexagonal wurtzite structure of ZnO thin films. AFM depicts that roughness and grain size of the ZnO films increase with increase in the films thickness. The direct optical band gap of the ZnO films calculated using Tauc's plot increase from 3.28 eV to 3.34 eV as the thickness of the films varies from 55 nm to 220 nm. The high quality c-axis orientated ZnO thin films with minimum strain and tuneable optical properties could be used as a transparent conducting oxide (TCO) for optoelectronic applications.