The structural, linear and nonlinear optical properties of high-quality Zn_1-xPb_xO nanostructured thin films for optoelectronic device applications

Abstract

In this article, the authors are presented the work on the evaluation of structural and third-order nonlinear optical (NLO) properties of lead (Pb)-doped zinc oxide (ZnO) thin films. The nano structured Zn_1-xPb_xO thin films were lay down on the glass substrate at an heating temperature of 350 °C with different Pb-doping concentration (‘x’ ratios of 0, 0.01, 0.05 and 0.1 wt. % of Pb) using the standard spray pyrolysis technique. The powder X-ray diffraction (P-XRD) spectroscopic analysis reveals the polycrystalline existence in the lead doped thin films in evidence with the hexagonal structure. The reformed grain sizes with enhanced doping content was perceived through surface morphological analysis with the help of field emission scanning electron microscopy and are in line with the X-Ray diffraction observations. The upgraded optical band gaps (Eg) were inferred through UV–Vis spectroscopic studies for the tailored films from 3.21 eV (pure ZnO) to 3.34 eV (10 wt. % of Pb). The defect states appearances and photoluminescence properties are discussed for the fabricated thin films using the resulted room temperature photoluminescence (RTPL) spectroscopic data. The third-order NLO parameters were calculated by potentially exposing the prepared thin films to the z-scan analysis under a continuous wave solid state laser at an excitation wavelength of 532 nm. The reverse saturable absorption, excited state absorption and self-defocusing effects were observed from the z-scan test along with the elevated nonlinear absorption coefficient (β) from 4.74 × 10^–4 to 1.05 × 10^–3 (cm/W) and negative nonlinear refractive index ${(n}_{2}$) from 1.42 × 10^–8 to 5.60 × 10^–8 (cm²W⁻¹). In addition to this, the third-order NLO susceptibility (χ ⁽³⁾) values are also calculated and are augmented from 0.82 × 10^–5 to 1.45 × 10^–4 (esu). An optical limiting (OL) topography with the limiting thresholds was also explored at the experimental wavelength. Hence, the outcome of structural, linear and nonlinear optical studies acknowledged the ability of the Zn_1-xPb_xO thin films in the field of optoelectronic device applications.