Laser-Induced Noble Metal-Semiconductor Nanocomposites And Their Optical Characteristics

Noble metals and semiconductor nanomaterials are widely used in the fields of optoelectronic devices,photocatalysis,biological detection and nonlinear optics due to their unique physical and chemical properties.In order to acquire the needs of different fields,the morphology and structure of nanomaterials need to be modified to improve their optoelectronic properties.Pulsed Laser Ablation(PLA)is a new type of nanomaterial synthesis technology.It does not require surface stabilizers(including surfactants,coupling agents,etc.)to obtain molded nanomaterials and only in one step.It has the advantages of high efficiency,low cost,and wide application range,which has attracted more and more attention.Based on PLA technology,we have prepared Al/Cu bimetallic nanoparticle films,ITO micro-hole arrays films and ITO/Au nanocomposite films.We explored the influence of different laser parameters on the film,and realized the control of the surface morphology and structure.Carried out its application in the field of surface enhanced Raman scattering(SERS)and nonlinear absorption.The main content and results of the thesis research are listed as following:(1)Tunable surface plasmon resonance of Al-Cu bimetallic nanoparticles thin films induced by pulsed laser.The surface morphology,roughness and NPs distribution of the Al/Cu bimetallic NPs thin films are dependent on the thickness of Al layer and Cu layer.The tunability of both localized surface plasmon resonance(LSPR)wavelength and intensity were realized by varying the pulse shot or relative thickness of Al/Cu bilayers.The experimental results show that the LSPR characteristic of the bimetallic nanoparticle film enhances the local surface electric field,and the defective Cu _XO induces the charge transfer between the probe molecule and the SERS substrate.The synergistic effect of electromagnetic field enhancement and chemical enhancement enhances the Raman signal of the detection molecule.(2)Selective PLA induces ITO micro-hole arrays films.We used a mode-locked picosecond laser to study the nonlinear absorption properties of ITO films and ITO micro-hole arrays films at the wavelength of 1550 nm.In addition,the surface morphology,crystal structure,optical absorption,dielectric constant and simulated electric field of the sample were also investigated.In particular,the wavelength range of the dielectric constant of ENZ can be tuned in the range of 1100～1350nm.Compared with the as-deposited ITO film,the surface electromagnetic field intensity of the ITO micro-hole arrays film is affected by the distribution of micro-hole.These samples exhibit tunable nonlinear saturation absorption characteristics.(3)PLA induced ITO/Au nanocomposite film and its optical properties.ITO films modified with Au NPs were prepared based on PLA.The nonlinear optical response of ITO films,Au films and ITO/Au composite films were investigated at the wavelength of1064 nm using a mode-locked picosecond laser.In the Z-scan measurement,the enhanced anti-saturable absorption phenomenon was observed,which was attributed to the LSPR characteristic of Au NPs and the enhanced electromagnetic field of Au NPs at the interface of the ITO film.This work provides new ideas for studying the nonlinear optics of metal/semiconductor nanocomposite structure,and promotes the development and application of plasma-based nonlinear photonics devices.