Preparation Of Semiconductor Nanocomposite Films And Study On Third-order Nonlinear Optical Properties

In this paper,CdSe/Al₂O₃/Ag and CdSe/PMMA/Ag composite films were prepared by magnetron sputtering and spinning coating.Scanning electron microscopy?SEM?and transmission electron microscopy?TEM?were used to characterize and analyze the morphology and structure of the materials.The linear and nonlinear optical properties of the samples were studied by ultraviolet-visible spectrophotometer?UV-VIS,?=200nm-800nm?,fluorescence spectrometer and femtosecond Z-scan technique.The experimental conditions were changed to explore the effects of different contents of Ag nanoparticles and CdSe quantum dots on the optical properties of the composite films.The main results are as follows:The particles of CdSe/Al₂O₃/Ag and CdSe/Al₂O₃/Ag composite films prepared by magnetron sputtering and spin-coating distributed evenly.With the increasing of DC sputtering power,the particle size of Ag nanoparticles increased,the particles became more uniform,and the films became denser.After annealing,the particle size of Ag films was larger,and the density of the films decreased.The linear absorption characteristics of the samples were measured by UV-VIS and the bandgap was calculated by formula.Compared with CdSe quantum dots,the linear absorption peaks of CdSe/Al₂O₃/Ag and CdSe/PMMA/Ag composite films were blue-shifted and the bandgap increased.The results of the femtosecond Z-scan indicated that with the increasing of Ag sputtering power,the nonlinear absorption and nonlinear refraction characteristics of the CdSe/Al₂O₃/Ag and CdSe/PMMA/Ag composite films were enhanced,and the third-order nonlinear polarizability increased.With the layers of CdSe quantum dots increasing,the third-order nonlinear optical properties of the two composite films weakened and the nonlinear polarizability decreased.Compared with CdSe quantum dots,the third-order nonlinear polarizability of CdSe/Al₂O₃/Ag and CdSe/PMMA/Ag composite films is increased by 10³-10⁴ times,and the third-order nonlinear optical properties of CdSe/PMMA/Ag composite films are better than that of CdSe/Al₂O₃/Ag composite films.