Nonlinear response of sodium and potassium doped ZnO along with improvement in bandgap structure: A combined physicochemical study

Abstract

In this study, zinc oxide nanoparticles have been synthesized in the presence of alkali hydroxides (NaOH and KOH) using the Sol-Gel method. The XRD, DLS, Z-scan, and UV–Vis spectroscopy were used to investigate nanoparticles' structural and optical properties. XRD diffraction patterns show enhancement in structural constants by adding sodium and especially potassium atoms. Correspondingly, the bandgap energy reduces because of decreasing the lattice energy. Also, the nonlinear absorption coefficient is measured using the z-scan technique, and it is found that reverse saturable absorption (RSA) is the prominent nonlinear optical phenomenon in this samples upon increasing the power of the incident laser beam and the magnitude of nonlinear absorption coefficient enhance by introducing Na and K atoms into the ZnO (named as NZO and KZO, respectively) crystal lattice. In accordance with the enhancement of nonlinear absorption processes, NZO and KZO are bestowed with optical bistability characteristics, which is beneficial for manufacturing optical switchers.