Electrochemical Sol-gel Preparation Of Composite Thin Films With Optical Nonlinearity

Nonlinear optical materials are widely used in optical information technology, lasertechnology, material analysis, nano photon technology and other fields. It is veryimportant to research and develop materials with excellent third-order nonlinear opticalproperties. In this dissertation, Te/TeO2-SiO₂composite films and Cu/SiO₂compositefilms were prepared by using electrochemical sol-gel method. The composition,structure and third-order optical nonlinearities of the as-prepared films werecharacterized.The stable transparent TeO2-SiO₂composite sol was prepared by usingtetraethoxysilane as sicilic source, tellurium isopropoxide or tellurium dioxide astellurium source, respectively. The composite films were obtained by electrochemicalsol-gel method from the prepared composite sol used as electrolyte bath. Theas-prepared films were confirmed as Te/TeO2-SiO₂by the electrochemistry, SEM/EDSand XRD characterizations. Combining with linear optical parameters and thickncss ofcomposite films, the third-order nonlinear optical properties of Te/TeO2-SiO₂compositefilms was tested by Z-scan method, whose results revealed that the third-order nonlinearoptical susceptibility χ（3）reached107¹06esu.A stable transparent CuCl2-SiO₂composite sol was prepared by using copperchloride and tetraethoxysilane as precursors. By using the composite sol as electrolytebath, composite films were obtained by electrochemical sol-gel method. The compositefilms were characterized as Cu/SiO₂composite films by the electrochemistry,SEM/EDS and XRD results. The third-order nonlinear optical susceptibility χ（3）of theas-prepared Cu/SiO₂composite films reached107¹06esu, which indicated that thethird-order nonlinear optical properties of the films are excellent.The electrodeposition and electrocrystallization of tellurium from TeO2sol andaqueous solutions and of copper from CuCl2sol and aqueous solutions on glass carbonelectrode were investigated by utilizing cyclic voltammetry and chronoamperometry,respectively. The adsorption-nucleation model was proposed to analyze quantitativelythe current-time transient curves. The results indicated that reduction of TeO2waspromoted in silica sol, tellurium electrocrystallization mechanism was characterized asinstantaneous nucleation with3D growth （3DI） under diffusion control in bothelectrolytes, and the nuclear number density of Te in sol was smaller than that in the aqueous solution at the same potential. The results also indicated that Cu2+reduced toCu+（the deposition rate determining step） in silica sol was easier than that in aqueoussolution, copper electrocrystallization mechanism was characterized as progressivenucleation with3D growth （3DP） under diffusion control in both electrolytes, thediffusion coefficient of copper ions in silica sol was smaller than that in aqueoussolution, but the saturated nuclear number density of Cu in sol was larger than that inthe aqueous solution at the same potential.