Conductive Nanofiber Web Film with Polydimethylsiloxane Sidewalls Selectively Coated through a Plasma Process for High Performance Flexible Transparent Electrodes.

Transparent electrodes are commonly used in various applications, such as solar cells, touch screens, smart windows, wearable electronic devices, and rollable flexible displays. Currently, indium tin oxide (ITO) is widely used as a transparent electrode material. However, ITO is not suitable for next-generation transparent electrodes that require flexibility; therefore, alternative nanomaterials, such as carbon nanotubes, conductive polymers, and metal nanowires, are being studied.

Hierarchical Self-Assembly of Perylene Diimide (PDI) Crystals.

Controlling molecular self-assembly of organic semiconductors is a key factor in enhancing the performance of organic electronics and optoelectronics. However, unlike various p-type organic semiconductors, it has proven elusive to control molecular self-assembly with about tens of nm dimensions using n-type organic semiconductors including perylene diimide (PDI), which is the most promising alternative to fullerene derivatives, without using an additional synthetic method or additives, thus far. Here, we developed a simple self-assembling method for the hierarchical self-assembly of PDI crystals with nanometer-to-micrometer scale features using pristine PDI-C8 without using an additional synthetic method or additive.

Recent Progress in Simple and Cost-Effective Top-Down Lithography for ≈10 nm Scale Nanopatterns: From Edge Lithography to Secondary Sputtering Lithography.

The development of a simple and cost-effective method for fabricating ≈10 nm scale nanopatterns over large areas is an important issue, owing to the performance enhancement such patterning brings to various applications including sensors, semiconductors, and flexible transparent electrodes. Although nanoimprinting, extreme ultraviolet, electron beams, and scanning probe litho-graphy are candidates for developing such nanopatterns, they are limited to complicated procedures with low throughput and high startup cost, which are difficult to use in various academic and industry fields. Recently, several easy and cost-effective lithographic approaches have been reported to produce ≈10 nm scale patterns without defects over large areas.

Polyelemental Nanolithography via Plasma Ion Bombardment: From Fabrication to Superior H Sensing Application.

The development of complex nanostructures containing a homo- and heteromixture of two or more metals is a considerable challenge in nanotechnology. However, previous approaches are considerably limited to the number of combinations of metals depending on the compatibility of elements, and to the complex shape control of the nanostructure. In this study, a significant step is taken toward resolving these limitations via the utilization of a low-energy argon-ion bombardment.

Correction: A three-dimensional metal grid mesh as a practical alternative to ITO.

Correction for 'A three-dimensional metal grid mesh as a practical alternative to ITO' by Sungwoo Jang et al., Nanoscale, 2016, 8, 14257-14263.

Universal Nanopatterning Technique Combining Secondary Sputtering with Nanoscale Electroplating for Fabricating Size-Controllable Ultrahigh-Resolution Nanostructures.

Here, we describe a next-generation lithographic technique for fabricating ultrahigh-resolution nanostructures. This technique makes use of the secondary sputtering phenomenon of plasma ion etching and of nanoscale electroplating to finely control the resolution of the fabricated structures from ten nanometers to hundreds of nanometers from a single microsized master pattern. In contrast to previously described techniques that incorporate a recently developed secondary sputtering lithography (SSL) patterning approach, which could only yield 10 nm-resolution structures, in the current technique, we used an improved SSL approach to produce various-sized, high-resolution structures.

Fabrication of three-dimensional hybrid nanostructure-embedded ITO and its application as a transparent electrode for high-efficiency solution processable organic photovoltaic devices.

Well-aligned, high-resolution (10 nm), three-dimensional (3D) hybrid nanostructures consisting of patterned cylinders and Au islands were fabricated on ITO substrates using an ion bombardment process and a tilted deposition process. The fabricated 3D hybrid nanostructure-embedded ITO maintained its excellent electrical and optical properties after applying a surface-structuring process. The solution processable organic photovoltaic device (SP-OPV) employing a 3D hybrid nanostructure-embedded ITO as the anode displayed a 10% enhancement in the photovoltaic performance compared to the photovoltaic device prepared using a flat ITO electrode, due to the improved charge collection (extraction and transport) efficiency as well as light absorbance by the photo-active layer.

New approach for fabricating hybrid-structured metal mesh films for flexible transparent electrodes by the combination of electrospinning and metal deposition.

In this study, hybrid-structured metal mesh (HMM) films as potential flexible transparent electrodes, composed of aligned micro-sized metal fibers integrated into random network of metal nanofibers, were fabricated by the combination of electrospinning and metal deposition. These naturally fiber-bridged HMMs, with a gold layer thickness of 85 nm, exhibited a high transmittance of around 90% and a sheet resistance of approximately 10 Ω sq, as well as favorable mechanical stability under bending stress. These results demonstrate that the approach employed herein is a simple, highly efficient, and facile process for fabricating, uniform, interconnected fiber networks with potential for producing high-performance flexible transparent electrodes.

Complex High-Aspect-Ratio Metal Nanostructures by Secondary Sputtering Combined with Block Copolymer Self-Assembly.

High-resolution (10 nm), high-areal density, high-aspect ratio (>5), and morphologically complex nanopatterns are fabricated from a single conventional block copolymer (BCP) structure with a 70 nm scale resolution and an aspect ratio of 1, through the secondary-sputtering phenomenon during the Ar-ion-bombardment process. This approach provides a foundation for the design of new routes to BCP lithography.

A three-dimensional metal grid mesh as a practical alternative to ITO.

The development of a practical alternative to indium tin oxide (ITO) is one of the most important issues in flexible optoelectronics. In spite of recent progress in this field, existing approaches to prepare transparent electrodes do not satisfy all of their essential requirements. Here, we present a new substrate-embedded tall (∼350 nm) and thin (∼30 nm) three-dimensional (3D) metal grid mesh structure with a large area, which is prepared via secondary sputtering.

High-Resolution p-Type Metal Oxide Semiconductor Nanowire Array as an Ultrasensitive Sensor for Volatile Organic Compounds.

The development of high-performance volatile organic compound (VOC) sensor based on a p-type metal oxide semiconductor (MOS) is one of the important topics in gas sensor research because of its unique sensing characteristics, namely, rapid recovery kinetics, low temperature dependence, high humidity or thermal stability, and high potential for p-n junction applications. Despite intensive efforts made in this area, the applications of such sensors are hindered because of drawbacks related to the low sensitivity and slow response or long recovery time of p-type MOSs. In this study, the VOC sensing performance of a p-type MOS was significantly enhanced by forming a patterned p-type polycrystalline MOS with an ultrathin, high-aspect-ratio (∼25) structure (∼14 nm thickness) composed of ultrasmall grains (∼5 nm size).

Macroscopic alignment of chromonic liquid crystals using patterned substrates.

We demonstrate an efficient technique to align lyotropic chromonic liquid crystals (LCLCs) using secondary sputtering lithography (SSL). Monodomains of LCLCs prepared using SSL maintained their stable alignment for days. A generalization of Berreman's theory was employed to determine the anchoring strength of LCLCs on tessellated surface patterns.

Highly Enhanced Fluorescence Signals of Quantum Dot-Polymer Composite Arrays Formed by Hybridization of Ultrathin Plasmonic Au Nanowalls.

Enhancement of the fluorescence intensity of quantum dot (QD)-polymer nanocomposite arrays is an important issue in QD studies because of the significant reduction of fluorescence signals of such arrays due to nonradiative processes in densely packed polymer chains in solid films. In this study, we enhance the fluorescence intensity of such arrays without significantly reducing their optical transparency. Enhanced fluorescence is achieved by hybridizing ultrathin plasmonic Au nanowalls onto the sidewalls of the arrays via single-step patterning and hybridization.

Polymer-Layer-Free Alignment for Fast Switching Nematic Liquid Crystals by Multifunctional Nanostructured Substrate.

A novel polymer-layer-free system for liquid-crystal alignment is demonstrated by various shaped indium tin oxide (ITO) patterns. Liquid crystals are aligned along the ITO line pattern and secondary sputtering lithography can change the shape of the ITO line pattern. Different shapes can control the direction and size of the pretilt angle.

Well-defined and high resolution Pt nanowire arrays for a high performance hydrogen sensor by a surface scattering phenomenon.

Developing hydrogen (H2) sensors with a high sensitivity, rapid response, long-term stability, and high throughput is one of the critical issues in energy and environmental technology [Hübert et al. Sens. Actuators, B 2011, 157, 329].

Fabrication of sub-20 nm nano-gap structures through the elastomeric nano-stamp assisted secondary sputtering phenomenon.

We describe a highly efficient method for fabricating controllable and reliable sub-20 nm scale nano-gap structures through an elastomeric nano-stamp with an embedded ultra-thin pattern. The stamp consists of ultrahigh resolution (approximately 10 nm) and high aspect ratio (ca. 15) metal nano-structures, which are obtained by secondary sputtering lithography (SSL).

Fabrication of 10 nm-scale complex 3D nanopatterns with multiple shapes and components by secondary sputtering phenomenon.

We introduce an advanced ultrahigh-resolution (∼ 15 nm) patterning technique that enables the fabrication of various 3D high aspect ratio multicomponents/shaped nanostructures. This methodology utilizes the repetitive secondary sputtering phenomenon under etching plasma conditions and prepatterned fabrication control. The secondary sputtering phenomenon repetitively generates an angular distribution of target particles during ion-bombardment.

Fabrication of complex 3-dimensional patterned structures on a ∼10 nm scale from a single master pattern by secondary sputtering lithography.

We describe a highly efficient method for fabricating a variety of complex 3D nano-patterns from a single master pattern using secondary sputtering lithography, which is a 10 nm scale patterning method that we have developed. A rapid etching rate in the bottom part of the PS pillar during the RIE process can produce various nanostructure shapes and the PS residual layer thickness can influence various feature dimensions, due to the controlled RIE time leading to different PS layer thicknesses. This technique provides a highly effective method for producing various complex 3D patterns from a single master pattern.

Cylindrical posts of Ag/SiO₂/Au multi-segment layer patterns for highly efficient surface enhanced Raman scattering.

We fabricated a regular array of Ag/SiO₂/Au multi-segment cylindrical nanopatterns to create a highly efficient surface enhanced Raman scattering (SERS) active substrate using an advanced soft-nanoimprint lithographic technique. The SERS spectra results for Rhodamine 6G (R6G) molecules on the Ag/SiO₂/Au multi-segment nanopatterns show that the highly ordered patterns and interlayer thickness are responsible for enhancing the sensitivity and reproducibility, respectively, The multi-segment nanopattern with a silica interlayer generates significant SERS enhancement (~EF = 1.2 x 10⁶) as compared to that of the bimetallic (Ag/Au) nanopatterns without a dielectric gap (~EF = 1.

Label-free detection of DNA hybridization using pyrene-functionalized single-walled carbon nanotubes: effect of chemical structures of pyrene molecules on DNA sensing performance.

We investigate the effect of functional groups of pyrene molecules on the electrical sensing performance of single-walled carbon nanotubes (SWNTs) based DNA biosensor, in which pyrenes with three different functional groups of carboxylic acid (Py-COOH), aldehyde (Py-CHO) and amine (Py-NH2) are used as linker molecules to immobilize DNA on the SWNT films. UV/Visible absorption spectra results show that all of the pyrene molecules are successfully immobilized on the SWNT surface via pi-pi stacking interaction. Based on fluorescence analysis, we show that the amide bonding of amine terminated DNA via pyrene containing carboxylic groups is the most efficient to immobilize DNA on the nanotube film.

New top-down approach for fabricating high-aspect-ratio complex nanostructures with 10 nm scale features.

We describe a new patterning technique, named "secondary sputtering lithography" that enables fabrication of ultrahigh-resolution (ca. 10 nm) and high aspect ratio (ca. 15) patterns of three-dimensional various shapes.