Lithography

About: Lithography is a research topic. Over the lifetime, 23507 publications have been published within this topic receiving 348321 citations.

Nanoskiving: A New Method To Produce Arrays of Nanostructures

Abstract: This Account reviews nanoskiving--a new technique that combines thin-film deposition of metal on a topographically contoured substrate with sectioning using an ultramicrotome--as a method of fabricating nanostructures that could replace conventional top-down techniques in selected applications. Photolithography and scanning beam lithography, conventional top-down techniques to generate nanoscale structures and nanostructured materials, are useful, versatile, and highly developed, but they also have limitations: high capital and operating costs, limited availability of the facilities required to use them, an inability to fabricate structures on nonplanar surfaces, and restrictions on certain classes of materials. Nanoscience and nanotechnology would benefit from new, low-cost techniques to fabricate electrically and optically functional structures with dimensions of tens of nanometers, even if (or perhaps especially if) these techniques have a different range of application than does photolithography or scanning beam lithography. Nanoskiving provides a simple and convenient procedure to produce arrays of structures with cross-sectional dimensions in the 30-nm regime. The dimensions of the structures are determined by (i) the thickness of the deposited thin film (tens of nanometers), (ii) the topography (submicrometer, using soft lithography) of the surface onto which the thin film is deposited, and (iii) the thickness of the section cut by the microtome (> or =30 nm by ultramicrotomy). The ability to control the dimensions of nanostructures, combined with the ability to manipulate and position them, enables the fabrication of nanostructures with geometries that are difficult to prepare by other methods. The nanostructures produced by nanoskiving are embedded in a thin epoxy matrix. These epoxy slabs, although fragile, have sufficient mechanical strength to be manipulated and positioned; this mechanical integrity allows the nanostructures to be stacked in layers, draped over curved surfaces, and suspended across gaps, while retaining the in-plane geometry of the nanostructures embedded in the epoxy. After removal of the polymer matrix by plasma oxidation, these structures generate suspended and draped nanostructures and nanostructures on curved surfaces. Two classes of applications, in optics and in electronics, demonstrate the utility of nanostructures fabricated by nanoskiving. This technique will be of primary interest to researchers who wish to generate simple nanostructures, singly or in arrays, more simply and quickly than can be accomplished in the clean-room. It is easily accessible to those not trained in top-down procedures for fabrication and those with limited or no access to the equipment and facilities needed for photolithography or scanning-beam fabrication. This Account discusses a new fabrication method (nanoskiving) that produces arrays of metal nanostructures. The defining process in nanoskiving is cutting slabs from a polymeric matrix containing embedded, more extended metal structures.

Lignin Laser Lithography: A Direct-Write Method for Fabricating 3D Graphene Electrodes for Microsupercapacitors

Abstract: DOI: 10.1002/aenm.201801840 inspired by the fabrication technology used in the semiconductor industry. The electrode materials of MSCs can be prepared by various, well-developed techniques, such as inkjet printing,[5–8] screen printing,[9,10] electrophoretic deposition,[11] electrodeposition,[12,13] and laser scribing.[14,15] Compared with other techniques, laser scribing technology is a simple direct-write method that does not require photolithography masks or tedious multistep fabrication processes.[16–23] In previous studies, graphene films were prepared from hydrated graphene oxide (GO) through laser scribing technology,[14,24] where GO could be reduced to rGO through the laser scribing process. However, the preparation of GO is complicated and time consuming. A more simple and direct approach is laser-scribing polyimide, which was developed by Tour and co-workers who fabricated laser-scribed graphene (LSG) electrodes from commercial Kapton polyimide film.[15] Different from thermal carbonization method, the laser scribing carbonization of polyimide provides LSG with highly porous graphene structure and high conductivity. Since then, LSG has been used in microsupercapacitor,[25–30] electrocatalytic hydrogen generation,[31,32] electrochemical oxygen evolution,[33] sensors,[34–36] and antimicrobial applications.[37,38] Recently, Tour and co-workers have done some excellent work that extended the laser scribing technology to wood and several polymers to make porous graphene films.[37,39] Polysulfone-class polymers have been transformed into graphene by one-step laser scribing, and various natural products, textile fabrics, and even bread have been transformed into graphene by multiple-laser-scribing technology.[40] As one of the three ingredients of natural biomass (lignin, cellulose, and hemicellulose), lignin is the most abundant renewable natural aromatic polymer existing in the world. Lignin is a kind of phenylpropane-based complex reticular aromatic poly mer and cannot be utilized by traditional chemical-engineering routes. Most existing lignins are extracted by sulfite pulping in the paper industry as a by-product pollutant in “black liquor.” As a result, lignin is usually considered to be useless and even as an environmental contaminant. Thus, the transformation of In this work, a simple lignin-based laser lithography technique is developed and used to fabricate on-chip microsupercapacitors (MSCs) using 3D graphene electrodes. Specifically, lignin films are transformed directly into 3D laser-scribed graphene (LSG) electrodes by a simple one-step CO2 laser irradiation. This step is followed by a water lift-off process to remove unexposed lignin, resulting in 3D graphene with the designed electrode patterns. The resulting LSG electrodes are hierarchically porous, electrically conductive (conductivity is up to 66.2 S cm−1), and have a high specific surface area (338.3 m2 g−1). These characteristics mean that such electrodes can be used directly as MSC electrodes without the need for binders and current collectors. The MSCs fabricated using lignin laser lithography exhibit good electrochemical performances, namely, high areal capacitance (25.1 mF cm−2), high volumetric energy density (≈1 mWh cm−3), and high volumetric power density (≈2 W cm−3). The versatility of lignin laser lithography opens up the opportunity in applications such as on-chip microsupercapacitors, sensors, and flexible electronics at large-scale production.

Fabrication of Superhydrophobic and Oleophobic Surfaces with Overhang Structure by Reverse Nanoimprint Lithography

Abstract: This work reports the fabrication of superhydrophobic and oleophobic surfaces with an overhang structure by reverse nanoimprint lithography. An overhang structure is difficult to fabricate by conventional lithography; however, it was conveniently formed by reverse imprint lithography, employed in conjunction with reactive ion etching. The obtained overhang structure was coated with a fluoroalkylsilane monolayer to reduce its surface energy. Further, four different types of nanopatterns were separately embedded on the surface of the obtained overhang structure by modified reverse imprint lithography to enhance its oil-repelling properties. The embedded nanopatterns resulted in different overhang angles, thereby enhancing the oil-repelling properties. The morphology and wetting characteristics of the overhang structure were investigated by scanning electron microscopy and contact angle measurements. This study demonstrates that an overhang structure can be successfully fabricated on a substrate by reverse n...