In this paper, a theoretical simulation based on a finite-difference time-domain method (FDTD) shows that the solar absorber can reach ultra-broadband and high-efficiency by refractory metals titanium (Ti) and titanium nitride (TiN). In the absorption spectrum of double-size cross-shaped absorber, the absorption bandwidth of more than 90% is 1182 nm (415.648–1597.39 nm). Through the analysis of the field distribution, we know the physical mechanism is the combined action of propagating plasmon resonance and local surface plasmon resonance. After that, the paper has a discussion about the influence of different structure parameters, polarization angle and angle of incident light on the absorptivity of the absorber. At last, the absorption spectrum of the absorber under the standard spectrum of solar radiance Air Mass 1.5 (AM1.5) is studied. The absorber we proposed can be used in solar energy absorber, thermal photovoltaics, hot-electron devices and so on.

Structural colors based on all-dielectric metasurfaces hold great promise for a wide range of applications, including high-density optical storage, ultra-high-resolution 3D displays, imaging security certification, and so on. However, achieving dynamic tunable structural color with a compact and simple Si platform remains a great challenge. Here, we propose a dynamic tunable structural coloration with polarization-sensitive metasurfaces consisting of arrays of Si elliptical nanopillars, enabling full-colored images to be displayed and switched through the control of the polarization of incident light. A distinct feature of our design is that the color phase is independent of the viewing angle, which is fundamental for real applications. Moreover, we demonstrated that dual and multiple colors can be obtained by varying the angle of either the polarizer or the analyzer. Our scheme provides a simple yet general approach for potential applications in the fields of virtual reality, ultra-high-resolution 3D displays, and high-density information storage.

Structural colorations with all-dielectric metasurfaces provide a dye-free approach for integrated sub-wavelength color generation with enhanced stability and environmental friendliness. However, it remains challenging to simultaneously tailor all the elementary color functions, hue, saturation, and brightness, in a simple platform. Here, we report a generic principle to create bright-field full-color nanoprinting with brightness control by using all-dielectric metasurfaces consisting of arrays of Si elliptical nanopillars. It is demonstrated that the lower order Mie resonances in the reflection spectra redshift with the sizes of the elliptical nanopillars when the incident light polarization is fixed along the major or minor axes. By designing the structure carefully, basic colors, such as red, green, blue, and yellow, are obtained across the visible spectrum. Experimental measurements show that the fabricated colors are independent with respect to the viewing angle owing to the Mie resonance origin. Moreover, we demonstrate that, by varying the angle of either the polarizer or the analyzer, the resonant wavelengths keep invariant while the reflection intensity decreases, leading to the tuning of the brightness of colors from bright to dark without changing the hue and saturation. Our scheme provides a simple yet general approach for the full hue, saturation, brightness control of structural colors, holding great potential in diverse applications, such as anti-counterfeiting technologies, 3D displays, and information storage.

Silicon structures with ultra-high aspect ratios have great potential applications in the fields of optoelectronics and biomedicine. However, the slope and increased roughness of the sidewalls inevitably introduced during the use of conventional etching processes (e.g., Bosch and DRIE) remain an obstacle to their application. In this paper, 4-inch wafer-scale, ultra-high aspect ratio (>140:1) microscale silicon structures with smooth sidewalls are successfully prepared using metal-assisted chemical etching (MacEtch). Here, we clarify the impact of the size from the metal catalytic structure on the sidewall roughness. By optimizing the etchant ratio to accelerate the etch rate of the metal-catalyzed structure and employing thermal oxidation, the sidewall roughness can be significantly reduced (average root mean square (RMS) from 42.3 nm to 15.8 nm). Simulations show that a maximum exciton production rate (G_max) of 1.21 × 10²⁶ and a maximum theoretical short-circuit current density (J_sc) of 39.78 mA/cm² can be obtained for the micropillar array with smooth sidewalls, which have potential applications in high-performance microscale photovoltaic devices.

Field-effect transistors based on organic semiconducting materials (OFETs) have unique advantages of intrinsically mechanical flexibility, simple preparation process, low manufacturing cost, and large-area preparation. Through the innovation of new material design and device structures, the performance of device parameters such as mobility, on–off current ratio, and the threshold voltage (V_TH) of OFETs continues to improve. However, the V_TH shift of OFETs has always been an important problem restricting their practical applications. In this work, we observe that the V_TH of polymer OFETs with the widely investigated device structure of a SiO₂ bottom-gate dielectric is noticeably shifted by pre-applying a large gate voltage. Such a shift in V_TH remains to a large extent, even after modifying the surface of the SiO₂ dielectric using a hexamethyldisilazane (HMDS) self-assembled monolayer. This behavior of V_TH can be ascribed to the charge trappings at the bulk of the SiO₂. In addition, the generality of this observation is further proven by using two other conjugated polymers including p-type PDPP3T and n-type PTzNDI-2FT, and a similar trend is obtained.

Unlike the optical information taken from a single in-focus image of general optical microscopy, through-focus scanning optical microscopy (TSOM) involves scanning a target through the focus and capturing of a series of images. These images can be used to conduct three-dimensional inspection and metrology with nanometer-scale lateral and vertical sensitivity. The sensitivity of TSOM strongly depends on many mechanical and optical factors. In this study, how illumination polarization and target structure affect the sensitivity of TSOM is analyzed. Firstly, the complete imaging procedure of the polarized light is investigated. Secondly, through-focus scanning results of different targets with two illumination polarizations are simulated using the finite-difference time-domain method. Thirdly, a few experiments are performed to verify the influence of illumination polarization and target structures on the sensitivity of TSOM. Both the results of the simulation and experiments illustrate an apparent influence of polarization on the sensitivity of inspecting the targets with center asymmetric structures. For enhanced sensitivity, illumination polarization should be perpendicular to the target texture. This conclusion is meaningful to adjust illumination polarization purposefully for different structure characteristics and improve the sensitivity of metrology.