| Depending on the mechanism of color formation,colors can be categorized into two types.As a traditional source of color production,chemical color has the advantages of low price and large-scale production,but also has the disadvantages of environmental pollution and easy fading.Compared with chemical colors,structural colors are derived from diffraction and scattering effects of structures comparable to visible light waves,and have the advantages of high saturation,colorfastness and green environmental protection,so they have been widely studied.Ultrathin films have the advantages of deep subwavelength(less than one-tenth of the wavelength),spectrum does not change with Angle,and easy preparation.In recent years,ultrathin films have become a research hotspot in optics,such as photodetectors,solar cells,structural colors and other fields.Previous studies have shown that the structural color of the ultrathin film is determined by the interface between the ultrathin film and the substrate,and the control parameters are limited.In this paper,we introduce the composite substrate composed of different metal films,and study the influence of gold,silver,copper,titanium,aluminum metal materials as ultrathin film substrates on the structure color of metal/metal Germanium/silicon three-layer ultrathin film.At the same time,the skin effect of germanium metal on ultrathin film structure color was also studied.In the first chapter,the background of color is briefly introduced,including the calculation method of X,Y,Z tristimulus value,X,Y chromaticity coordinates and CIE chromaticity map.At the same time,this chapter reviews the research status of ultrathin film structural color.At last,the paper introduces the significance of the topic,the research content and the main work of this paper.The structural color of ultrathin film is determined by the interface between ultrathin film and substrate.Existing studies have not explored the influence of interface on color.In this work,a composite substrate composed of different metal films is introduced to increase the regulatory parameters.The effects of different interfaces on the structure color of metal/germanium/silicon thin films were investigated.The skin effect of germanium on the structure color of superthin films was also studied.In chapter 2,we introduce the research theory of thin film structure.The difference of reflectance R between S-polarized light and P-polarized light at normal and oblique incidence is discussed.The skin depth calculation of materials is introduced briefly.The calculation formula is:L=1/α=λ/4πkIn chapter 3,we study the influence of skin depth on structure color by changing the thickness of metal film in two types:greater than skin depth and less than skin depth.The influence of interface on structure color was studied by changing substrate type.At last,the influence of the incident Angle on the reflection spectrum of the three-layer ultrathin film structure is studied under S-polarized light and P-polarized light.The conclusion is that when the thickness of germanium is less than the skin depth,light will pass through the germanium film to the metal substrate,and the metal substrate is involved in the regulation of structure color.The color of the ultrathin film can be controlled by changing the type of metal substrate,the thickness of germanium and the thickness of silicon.When the thickness of germanium is greater than its skin depth in the visible range,the light will not pass through the germanium film to the metal substrate,and the metal substrate will not participate in the structure color regulation.Germanium was used as the new substrate.The metal substrate/germanium/silicon ultrathin film structure has good angular stability and does not produce iridescent effect.The fourth chapter of this paper summarizes the work and looks forward to the future of structural color. |
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