Size and Morphology Modulation in ZnO Nanostructures for Nonlinear Optical Applications: A Review

Morphology-richZnO as a direct band gap II-VI semiconductoris a promising material for photonic, optical, and electronic devices.Nanostructured materials have provided a leading edge to the next-generationtechnology due to their distinguished performances and efficienciesfor device fabrication. The nonlinear optical (NLO) properties andmechanisms dependent on the size and dimensionality of ZnO nanostructuresremain to be elucidated. Herein, we begin to provide a comprehensivesummary of the status of research activities in ZnO nanostructures,including their syntheses and potential applications, with an emphasison multidimensional ZnO nanostructure based growth, properties, andapplications. Density functional theory calculations confirmed theeffect of ZnO size, morphology, and defect on the structure, workfunction, and charge density distribution of the electron band. Finitedifference time domain simulation confirmed that the electric field,magnetic field, and Poynting vector of the ZnO system with the morphologychanges were applied. Moreover, the ultrafast NLO and carrier dynamicsof feature-rich ZnO nanostructures were studied. The effects of differentexperimental parameters on the morphology and linear and nonlinearexcitation and radiation mechanisms of ZnO nanostructures were studiedby constructing an electron transfer mechanism diagram and the Z-scan technique. The results show that the properties andproperties of ZnO nanostructures can be regulated and controlled bythe structure and morphology. The application and performance of feature-richzinc oxide nanostructures in photoelectric functional devices areprospected, which will provide valuable references and guidance forrelated researchers.