We report an all-printed flexible carbon nanotube (CNT) thin-film transistor (TFT). All the CNT TFT components,
including the source and drain electrodes, the TFT transport channel, and the gate electrode, are printed on a flexible
substrate at room temperature. A high ON/OFF ratio of over 103 was achieved. The all printed CNT-TFT also exhibits
bias-invariant transconductance over a certain gate bias range. This all-printed process avoids the conventional
procedures in lithography, vacuum, and metallization, and offers a promising technology for low-cost, high-throughput
fabrication of large-area flexible electronics on a variety of substrates, including glass, Si, indium tin oxide and plastics.
A high-speed flexible transistor made with an ultrapure carbon nanotube (CNT) solution is reported. The carrier transport layer of the CNT-based flexible transistor is formed at room temperature by dispensing a tiny droplet of an electronics-grade CNT solution. Ultra high field-effect mobility of ~ 48,000 cm2/(V×s) has been demonstrated on a thin-film field effect transistor (TFT). A simple trans-impedance voltage follower circuit was made using the CNT-TFT on a transparency film. The circuit exhibited a high modulation speed of 312 MHz and a large current-carrying capacity beyond 20 mA. The transparency and the sheet resistance of the CNT-film were also characterized at different wavelengths. The ink-jet printing-compatible process would enable mass production of large-area electronic circuits on virtually any desired flexible substrate at low cost and high throughput.
The research and development of organic materials for use in optical components and devices aims to take advantage of several unique properties of these materials, including their stability, tailorability, and flexibility. In this study, by carefully controlling the components, we have developed a material that offers significant advantages over common optical materials. Specifically, the new material has a high refractive index and is curable with ultraviolet (UV) light, solvent free, and transparent over a wide wavelength range. We applied the material to a substrate via spin coating, although other application methods are possible.
The production of optical components through press-patterning has received a large amount of attention. The low cost of replication and high throughput of the process provide the potential for low-cost optical components. Typically a metallic plate is patterned via electroplating or electroforming to produce a negative image on the plate. This plate is then pressed into the patternable material and subsequently treated to form the desired pattern in the organic material. Here we report our initial attempts at press-patterning structures into a UV-curable high refractive index material.
Press-patterning of polymers to yield optical structures is being pursued in optics and photonics to yield low-cost optical components. This is a promising technology for the low-cost and high-throughput fabrication of polymeric photonic components. The processing of such imprinted photonic components is usually done using a metallic shim where a pattern is generated on the shim by electroforming or electroplating. The shims are then used to replicate patterns on plastics and polymers under high temperatures and pressures. Under the correct conditions, the polymer flows and replicates a diffraction grating.
Polymeric diffraction gratings and holograms have applications in a multitude of photonic applications for diffractive optics. This requires materials that are transparent in the visible region, and preferably have relatively high refractive indices in order to achieve a high diffraction efficiency. In addition, in order to facilitate processing by the press-patterning method that will be further described in this paper, polymeric materials that are amenable to spin-coating and show good thermoplastic behavior are also desired.
Optically transparent, high-refractive index polyimides were tested for their ability to be processed and patterned using a press-patterning method. A process that allowed the materials to be patterned were developed, and measurements were taken to validate the results. Our initial results showed successful press-patterned polyimide films with grating structures having submicron line and trench widths and step heights of less than 0.5 microns.
Multi-layer lithography processes have been introduced to fabricate very fine structures over a topographic surface for advanced semiconductor device production. The first layer formed on the topographic surface is the planarization layer to provide surface planarity for additional thin layer(s) of material. Such materials could be a photoresist, a hardmask, or both with uniform film thickness for the lithography step to image the structures. However, the large size and distribution variation of the topography structures across the substrate surface have a major impact on the performance of the lithography processes. A new planarization process, contact planarization (CP), has been introduced to improve thickness uniformity and to provide global surface planarity for multi-layer lithography applications. This study focuses on planarizing an experimental organic 193-nm BARC layer on via wafers to minimize iso-dense film thickness bias and provide improved global surface planarity for the bilayer photolithography process. In addition, minimum thickness bias improves control of downstream processes such as plasma etching. This paper will discuss this unique planarization process and its performance with various thicknesses of the experimental 193-nm BARC on via wafers. The photolithography performance of the material and process will be discussed.