Stable field emission from nanoporous silicon carbide.

We report on a new type of stable field emitter capable of electron emission at levels comparable to thermal sources. Such an emitter potentially enables significant advances in several important technologies which currently use thermal electron sources. These include communications through microwave electronics, and more notably imaging for medicine and security where new modalities of detection may arise due to variable-geometry x-ray sources. Stable emission of 6 A cm(-2) is demonstrated in a macroscopic array, and lifetime measurements indicate these new emitters are sufficiently robust to be considered for realistic implementation. The emitter is a monolithic structure, and is made in a room-temperature process. It is fabricated from a silicon carbide wafer, which is formed into a highly porous structure resembling an aerogel, and further patterned into an array. The emission properties may be tuned both through control of the nanoscale morphology and the macroscopic shape of the emitter array.

Efficiency enhancement of organic solar cells using transparent plasmonic Ag nanowire electrodes.

Surface plasmon enhanced photo-current and power conversion efficiency of organic solar cells using periodic Ag nanowires as transparent electrodes are reported, as compared to the device with conventional ITO electrodes. External quantum efficiencies are enhanced about 2.5 fold around the peak solar spectrum wavelength of 560 nm, resulting in 35% overall increase in power conversion efficiency than the ITO control device under normal unpolarized light.

Large area high density sub-20 nm SiO(2) nanostructures fabricated by block copolymer template for nanoimprint lithography.

We developed simple fabrication methods to effectively transfer the block copolymer nanopatterns to a substrate material. High aspect ratio, sub-20 nm nanopillar and nanohole structures are successfully fabricated in a SiO(2) layer in large area format, and the versatile utilities of these nanostructures as nanoimprint molds are studied. Nanoimprint lithography using these molds makes it possible to easily replicate densely packed block copolymer nanotemplate patterns on arbitrary substrates in a short processing time by using a large variety of polymer materials, including functional materials such as conjugated polymers. In addition, the PDMS soft stamps with both nanohole and nanopillar pattern polarities, which are useful tools for soft lithography and transparent template applications, are also successfully fabricated using the pillar- and hole-type SiO(2) molds. These soft stamps provide an effective way to fabricate controllable as well as reproducible plasmonic metal nanostructures with tunable surface plasmon resonances.