Laser-Induced Nonlinear Optical Tunability of Al-Doped ZnO Thin Films for Optoelectronic Device Applications

In this study, spray pyrolysis is used to fabricate aluminium (Al) doped zinc oxide (ZnO) nano-structured thin films on a glass substrate at various concentrations (0,2,4,6,10,15 wt.%) with 430⁰C substrate temperature. The impact of aluminium on ZnO films was characterised by utilizing XRD and UV-Vis spectroscopy measuring tools. The study on pure ZnO demonstrated a wurtzite structure that is hexagonal in shape and a desire orientation of (101). Crystalline size of undoped ZnO thin film is determined to be 18.81 nm from Scherrer equation and 20.30 nm from W-H plot. D_avg value decreased from 16.1 nm to 13.06 nm doping concentration. Surface roughness for undoped, 2 wt.% and 15 wt.%, varies from 176 nm to 96.3 nm. The grain size of thin films varies from 20.67 nm to 38.34 nm as the concentration of aluminium rises. The optical measurements showed that Al doping resulted in a reduction in transmittance from 82% to 63%. The addition of aluminium to the deposits resulted in a systematic alteration in the absorption coefficient and refractive index. Photoluminescence spectra indicated the presence of several defect orientations in the films. The study focused on 3^rd order NLO features, including third order susceptibility χ³, nonlinear R.I n₂, and nonlinear absorption coefficient (β). The 3^rd order nonlinear susceptibility χ³ of 6 wt.% Al:ZnO thin films is 1.96×10^-6 (esu). It was found that Zn_0.96Al_0.04O nanofilm is better appropriate for optical limiter applications.