Optical Properties And Preparation Methods Of Two-dimensional Composite Colloidal Crystals

Photonic crystal is a kind of material with periodic and ordered structure.Due to a series of special optical properties such as photon band gap,slow photon effect.Photonic crystals can realize the regulation of light in the fields of new optical devices,anti-counterfeiting technology,information storage,sensors and other fields.Because of its advantages such as simple preparation,low cost,easy to chemically modified,colloidal photonic crystal is a hotspot in the field of photonic crystal.And several sensors,display devices,anti-fake pattern based on colloidal photonic crystal has been successfully developed.With the development of new materials and technology,heterojunction photonic crystals have more complex photonic band structure and more abundant optical properties.Photonic crystal hetero structure is composed of stacked photonic crystals of different materials or different optical band gaps.It has important application value in expanding optical band gaps and optoelectronic functional integrated devices,and becomes the focus of research in the field of photonic crystals.Preparation method for composite photonic crystal,this paper proposes a new method for preparing two-dimensional composite colloidal crystals.The prepared two-dimensional composite colloidal crystal will synthesize the different optical properties of the two materials,and can control the matching relationship between the particles through the etching process,and realize the variable refractive index duty cycle.Therefore,this method can adjust the forbidden band distribution of the photonic crystal according to the properties of the material and the duty ratio of the refractive index.At the same time,this method can break through the problem of simplification of the photonic band gap of a single material,and lay a foundation for the application of colloidal crystals of the composite material in photonic devices.This paper proposes a two-dimensional composite colloidal crystal structure model,and uses the finite difference time domain(FDTD)algorithm to study the optical properties of the structure.The Bragg diffraction theory provides a theoretical basis for investigating the optical properties between different materials.Using FDTD simulation software to construct several models of colloidal crystals and composite colloidal crystal and perform the simulation of the spectrum.Then by comparing the reflection spectrum of composite colloidal crystal with those of two materials respectively,and we get the conclusion that two-dimensional composite colloidal crystal can combine optical properties of two materials.In addition,this article introduces in detail the two-dimensional composite colloidal crystal structure of polystyrene material with large particle size and silica material with small particle size,which matches the materials used in the following experiments,and provides a theoretical basis for the subsequent research..A method and process for preparing two-dimensional composite colloidal crystals is proposed.Through many attempts and experimental preparations,the specific methods and processes of the preparation process were obtained.Firstly,using the air/water interface self-assembly method preparation of large area to create single-layer two-dimensional colloidal crystal polystyrene microspheres array(2-DCCA).Then,the method combines the reactive ion etching technology to improve the morphology of the self-assembled polystyrene particle layer and control the spacing of the micro spheres.The 2-DCCA composite colloidal crystal structure(2-DCCS)with double optical band gap can be obtained by self-assembly of 2-DCCA microspheres with different diameters and different materials according to their microsphere spacing.Next,the article introduces the preliminary preparations for the experiment: First,through reading literature and experiment to determine the appropriate solution formula of suspension colloid crystal.Secondly,we must pass experimental tests to determine the most appropriate injection rate,so that there is little or no crystallization during the injection process.Finally through continuous adjustment of etching time,by observing the microsphere size to find the most suitable etching time.This article also elaborated each step of the preparation method in detail.The article analyzes and tests the prepared two-dimensional composite colloidal crystals and studies its optical properties.Furthermore,the reflection spectra shows that the two-dimensional composite colloidal crystal combines the optical properties of the two materials,the matching relationship between particle and structural duty cycle can be controlled by the etching process.Therefore,the two-dimensional composite material will have important application value in the field of photonic devices.