Symmetric Thin Films Based on Silicon Materials for Angle‐Insensitive Full‐Color Structural Colors

Abstract

expensive photolithography, etching, and other processes. [22] Photonic crystal thin film interference technology provides a new solution. [23][24][25][26] The structural color based on photonic crystal technology does not require complex photolithography, etching and other steps, so it has significant advantages in preparation, cost, efficiency, and other aspects. This is also one of the important technologies that can be put into large-scale industrial production at present. The structural color based on thin film is usually achieved by successively depositing materials with different refractive indexes. The final thin films can present specific colors based on the multi-beam interference. When the structure, period number and thickness of the thin film change, the color of the photonic crystal thin film will also change. However, one problem of this technology is that the change of the incident angle leads to the change of the equivalent optical path, so that the reflection spectrum of the device will drift with the angle. This phenomenon of the color changing with angle limits the application of structural color.In recent years, a large amount of research discussed the angle insensitive structural colors. For example, Yang et al. used metals such as Al, W, Ge, Au, Ni, and the dielectric material Ta 2 O 5 to produce high-purity RGB reflective colors. [27] Lee et al. achieved transmitted structural colors with high efficiency and high color purity by using dielectric materials (ZnS) and metal (Ag). [28] Transmission peaks of the three colors (red, blue, and green) are between 50% and 70%, and it also has good angle insensitivity. By this means, various applications may be possible such as wearable displays, flexible electronics, image sensors, and decorations. However, using non-metallic materials to achieve angle insensitive structural color is also a great challenge. Meanwhile, the research on cyan, magenta, yellow (CMY) reflective structural colors with high reflection efficiency and high angle sensitivity is still not mature. Especially in recent years, due to stable color appearance, structural color has been applied more and more in coating, car paint, color printing, and other fields. [29][30][31][32][33][34][35][36] Structural color can present stable aesthetic color, therefore the study of CMY reflection color becomes more important. One problem that needs to be solved in this type of application is that the reflective colors on the front and back of the thin film need to be consistent. When solving this problem, it is often necessary to symmetrize the asymmetric Here, reflective full-color structural colors with symmetrical thin film structures made from all silicon-based materials are demonstrated. Considering practical application scenarios, the five-layer reflection enhancement unit located in the core of the device is composed of amorphous silicon (a-Si) and SiO 2 . Because of the large refractive index difference, the high reflection efficiency can be achieved, and the highest peak reflectivity o...

Microwave-Absorbing Foams with Adjustable Absorption Frequency and Structural Coloration

“…Two distinct peaks situated at 464.5 and 458.5 eV with a peak separation of 6.0 eV (Figure 2c) are attributed to Ti 2p 1/2 and Ti 2p 3/2 , respectively, which agrees with the XPS spectra of Ti 4+ . 28 The XPS characterization further demonstrates that the prepared TiO 2 /Ni/MF shows good homogeneity. Interestingly, the thermal decomposition temperature of TiO 2 /Ni/MF is higher than that of Ni/MF, implying that the TiO 2 coating can enhance the antioxidative properties of Ni/MF.…”

“…The structural coloration of TiO 2 /Ni/MF is mainly based on thin-film interference in which destructive interference light is reflected from the top and bottom interfaces of the films (Figure S8). Due to the larger index of the TiO 2 layer, the light is reflected with a near π-phase shift based on the half-wave loss theory. ,, This results in the strengthening of the total reflected light when integer multiples of its half wavelength in the TiO 2 /Ni/MF correspond to the TiO 2 thickness. The spectra of TiO 2 /Ni/MF also reveal different reflection peaks with varying TiO 2 thickness (Figure S9).…”

“…Due to the larger index of the TiO 2 layer, the light is reflected with a near π-phase shift based on the half-wave loss theory. 25,26,28 This results in the strengthening of the total reflected light when integer multiples of its half wavelength in the TiO 2 /Ni/MF correspond to the TiO 2 thickness. The spectra of TiO 2 /Ni/MF also reveal different reflection peaks with varying TiO 2 thickness (Figure S9).…”

Reflective Full‐Color Structural Colors with High Brightness and High Purity Based on Ge2Sb2Se4Te1 Chalcogenide Film

“…This strategy for color generation is highly tunable and scalable, and it can be easily scaled up utilizing vacuum deposition or electrodeposition systems. [ 18–20 ]…”

“…This strategy for color generation is highly tunable and scalable, and it can be easily scaled up utilizing vacuum deposition or electrodeposition systems. [18][19][20] One of the simplest and most extensively used thin-film configurations to generate structural colors is the Fabry-Perot (F-P) resonator, consisting of an optically transparent dielectric or highly absorbent semiconductor medium sandwiched between two metallic mirrors. [21][22][23] Constructive interferences occur in a dielectric spacer, thus forming a transmission peak or reflection valley at a specific wavelength.…”