The Design,Fabrication And Application Of Nano Color Media Based On F-P Cavities

The abundant colors are inseparable from the people's daily lives.Actually,the colorful images and multi-colored living organisms seen by the human eye are composed of a series of tiny color pixels.While the traditional color pixels are mainly obtained by dye pigments which are vulnerable to optical damage and are somewhat hazardous to the environment,thus restricting its application in the actual production and daily life.In recent years,more and more researchers have studied structural colors to achieve abundant color pixels.The structural colors are resulted from the physical processes such as interference,diffraction,scattering and so on,originating from the interactions between the incident light and the micro-nanostructures exiting on the surface of the objects.More and more studies have shown that structural-color-based pixels have broad application prospects in imaging,anti-counterfeiting,file security,furniture decoration,display and data storage because they offer the merits of good stability,environmental friendliness and their iridescent phenomenon.With the development of technology and industrial applications,exploring the full-color structural color pixels with high contrast and brightness and developing the new technology for the monolithic full-color integration become the hot topics in the field of full color printing.The study aims to achieve abundant structural color pixels based on the thin-film interference effect in the asymmetric F-P cavities and to explore its potential application in high resolution full-color printing.The main research results are summarized as follows:(1)A kind of large-area,lithography-free,reflective color filters based on asymmetric F-P cavities comprised of Ni-SiO2-Al triple-layer film stacks were designed.Enabled by the broadband absorption of Ni,the designed color filters can selectively reflect a specific wavelength in the visible region and have a super absorption with a maximum absorption intensity of?90%at the other wavelengths.Moreover,the spectral positions of reflection peaks can be tailored by adjusting the thickness of the SiO2 dielectric layer,resulting in achieving abundant colors with high saturation and brightness operating at the entire visible frequencies.Combined with grayscale patterning techniques,high-resolution over 50,000 dpi,high-contrast monolithic color printing could be achieved enabled by this reflective color-filter configuration.(2)A full-color printing concept based on the interference effect in pixelized metal-dielectric-metal Fabry-Perot(F-P)resonance cavities was demonstrated.The pixel color for printing is determined by the thickness of the dielectric layer in each microscale F-P cavity.Abundant colors with controllable brightness and saturation are achieved by varying both the thickness and the filling density of the F-P cavities using grayscale lithography.Enabled by the wide color gamut,a vivid full-color image can be reproduced at the microscopic scale with high resolution by correlating the colors with the dimensional parameters of the F-P cavities through a layout-generation algorithm.The color pixels based on interference effects provides a new opportunity to use artificial structures for color printing and also has the potential to be scale up for large-volume application in consumable products by using replica patterning techniques such as grayscale photolithography,nanoimprinting,and soft lithography.(3)Greatly extended color gamut could be achieved by precisely controlling both the size and period of the asymmetric F-P cavities at the same dielectric-film thickness.Without grayscale lithography,the interference color pixels covering the entire range of visible light with different brightness,hue,and saturation also could be printed.The color changes caused by different filling density(i.e.the ratio of size to period)of the F-P cavities can be explained by the effective-medium toy model.With decreased filling density,the effective refractive index of the dielectric layer decreases,so as to the effective optical path,resulting in the blueshift of the maximum absorption and reflection.These interference color pixels,as compared to the plasmon color pixels,exhibit greater advantages in fabricating,color gamut,and color contrast.In the future,combined with replica patterning techniques such as roll-to-roll imprinting and soft lithography,they have great potential to achieve large-scale full-color printing.(4)We adopted ultrathin palladium as a lossy metal layer to form asymmetric F-P cavities and evaluated their capability for reflective color filtering and colorimetric hydrogen sensing applications.Both experiment and numerical simulations showed that the ultrathin palladium based F-P cavities are able to produce a broad range of reflective colors with high brightness and contrast.A maximum reflectance of 90%can be achieved under constructive interference wavelength and almost perfect absorption is obtained at the destructive interference wavelength.These reflectance and absorption peaks can obviously shift under hydrogen asmosphere due to the transformation of palladium to hydrided palladium which has a distinct optical property.The results suggest that the ultrathin-palladium-based asymmetric F-P cavity can serve as a candidate for reflective color printing,colorimetric hydrogen sensing and optical anti-counterfeiting applications as standard structural color pixels.