Search

Functional nanostructures are exploited for a variety of cutting-edge fields including plasmonics, metasurfaces, and biosensors, just to name a few. Some applications require nanostructures with uniform feature sizes while others rely on spatially varying morphologies. However, fine manipulation of the feature size over a large area remains a substantial challenge because mainstream approaches to precise nanopatterning are based on low-throughput pixel-by-pixel processing, such as those utilizing focused beams of photons, electrons, or ions. In this work, we provide a solution toward wafer-scale, arbitrary modulation of feature size distribution by introducing a lithographic portfolio combining interference lithography (IL) and grayscale-patterned secondary exposure (SE). Employed after the high-throughput IL, a SE with patterned intensity distribution spatially modulates the dimensions of photoresist nanostructures. Based on this approach, we successfully fabricated 4-inch wafer-scale nanogratings with uniform linewidths of

The authors reported a facile, scalable, high-yield, universal fabrication approach for creating micro- and nanoscale metallic patterns for flexible electronic and plasmonic applications through imprint-transfer of catalytic Pd nanoparticles using a reusable imprint mold with selectively adsorbed catalytic nanoparticles and selective electroless deposition of metals. Metallic patterns are mass-produced on flexible plastics according to the predefined micro-/nanofeatures on the imprint mold without any chemical modification on the substrate, which significantly reduces both fabrication costs and environmental pollution, compared to other methods utilizing electroless deposition. The excellent dimensional scalability and material versatility of this method have been confirmed by fabricating metallic micromeshes with a linewidth down to 3 μm, and metallic nanodisk arrays with a pitch of 500 nm. Using this method, flexible transparent electrodes were constructed on Cu micromesh-patterned plastic films with transmittance values higher than 75% and sheet resistance values below 0.4 Ohms sq−1, as well as high figures of merit up to 4 × 103. This method is further demonstrated in the fabrication of flexible thin-film heaters, electroluminescent displays, and flexible printed circuits, as well as plasmonic refractometric sensors.

We report a large-scale surface with continuously varying wettability induced by ordered gradient nanostructures. The gradient pattern is generated from nonuniform interference lithography by utilizing the Gaussian-shaped intensity distribution of two coherent laser beams. We also develop a facile fabrication method to directly transfer a photoresist pattern into an ultraviolet (UV)-cured high-strength replication molding material, which eliminates the need for high-cost reactive ion etching and e-beam evaporation during the mold fabrication process. This facile mold is then used for the reproducible production of surfaces with gradient wettability using thermal-nanoimprint lithography (NIL). In addition, the wetting behavior of water droplets on the surface with the gradient nanostructures and therefore gradient wettability is investigated. A hybrid wetting model is proposed and theoretically captures the contact angle measurement results, shedding light on the wetting behavior of a liquid on structures patterned at the nanoscale.

We report stretchable metal-mesh transparent electrodes (TEs) with excellent electrical conductivity (2 Ω/sq) and optical transparency (80%) under up to 55% strain. The figures of merit on these electrodes, as defined as the ratio between electrical conductivity and optical conductivity, are among the highest reported for stretchable TEs under moderate stretching. Moreover, we demonstrate their application in a stretchable electroluminescent (EL) light-emitting film as top and bottom electrodes. EL lighting devices require low-resistance electrodes to unleash their potential for large-area low-power-consumption applications, in which our highly conductive and transparent stretchable TEs provide an edge on other competitor approaches. Importantly, our stretchable metal-mesh electrodes are fabricated through a vacuum-free solution-processed approach that is scalable for cost-effective mass production. We also investigate the fracture and fatigue mechanisms of stretchable metal-mesh electrodes with various mesh patterns and observe different behaviors under one-time and cyclic stretching conditions. Our solution-processed fabrication method, failure mechanism investigation, and device demonstration for metal-mesh stretchable TEs will facilitate the adoption of this promising high-performance approach in stretchable and wearable electronics applications.

A vacuum-free solution-processed fabrication strategy featuring templated electrodeposition and imprint transfer (TEIT) is developed for micro- and nanoscale metallic structures. Various functional devices, including metal-mesh transparent electrodes and plasmonic sensors, are demonstrated using this cost-effective and scalable manufacturing process.

Patterning high-aspect-ratio gratings by the phase-locked two-beam fiber-optic interference lithography (2-FOIL) is numerically and experimentally investigated in this paper. The Dill model is applied in the numerical simulation to understand the effects of an exposure dose and pattern contrast on the exposed photoresist grating profiles. Exposure experiments on the authors’ home-built 2-FOIL setup are conducted to demonstrate the suitability for manipulating the linewidth of photoresist gratings by tuning the exposure dose to achieve high aspect ratios over 6 at high pattern contrast thanks to the phase-locking mechanism. The high-aspect-ratio photoresist gratings serve as an excellent etching mask for the subsequent pattern transfer into underlying silicon substrates for high-aspect-ratio silicon gratings. Using these high-aspect-ratio silicon gratings as the nanoimprint mold, a square nanomesh is demonstrated by means of the multiple-step nanoimprint lithography. The authors’ work demonstrates that the proposed phase-locked 2-FOIL system enables high pattern contrast under long exposure duration, making it a suitable tool for fabricating high-aspect-ratio grating structures.Patterning high-aspect-ratio gratings by the phase-locked two-beam fiber-optic interference lithography (2-FOIL) is numerically and experimentally investigated in this paper. The Dill model is applied in the numerical simulation to understand the effects of an exposure dose and pattern contrast on the exposed photoresist grating profiles. Exposure experiments on the authors’ home-built 2-FOIL setup are conducted to demonstrate the suitability for manipulating the linewidth of photoresist gratings by tuning the exposure dose to achieve high aspect ratios over 6 at high pattern contrast thanks to the phase-locking mechanism. The high-aspect-ratio photoresist gratings serve as an excellent etching mask for the subsequent pattern transfer into underlying silicon substrates for high-aspect-ratio silicon gratings. Using these high-aspect-ratio silicon gratings as the nanoimprint mold, a square nanomesh is demonstrated by means of the multiple-step nanoimprint lithography. The authors’ work demonstrates that the...

A fast-reconfigurable and actively-stabilized fiber-optic interference lithography system is demonstrated in this paper. Employment of fiber-optic components greatly enhances the flexibility of the whole system, simplifies its optical alignment, and suppresses the interference of mechanical vibrations. Active stabilization is implemented in the system and evaluated through modeling and experiment. We demonstrate 3-inch-diameter wafer-scale patterning of 240-nm-period grating lines with a sub-50-nm linewidth and an aspect ratio over 3. Two-dimensional patterns of different geometries and dimensions are also demonstrated to show the versatility of our system. Step-and-repeat exposure is demonstrated with independently controlled patterning fields of 2×2cm2 large.