Fabrication of silica nanostructures with a microwave assisted direct patterning process.

Silica nanostructures were fabricated on glass substrate using a microwave assisted direct patterning (MADP) process, which is a variety of soft lithography. During the MADP process using polydimethylsiloxane (PDMS), mold and microwave heating are performed simultaneously. Blanket thin film and micro- to nano-sized structures, including moth-eye patterns of SiO2, which consisted of coalesced silica nanoparticles, were formed on glass substrates from SiO2 nano-particle dispersed solutions with varied microwave heating time. Optical properties and surface morphologies of micro-sized hemisphere, nano-sized pillar, moth-eye and 50 nm sized line/space silica patterns were measured using UV-vis and a scanning electron microscope. X-ray diffraction analysis of SiO2 thin films with and without microwave heating was also carried out.

Enhancement of outcoupling efficiency of organic light-emitting diodes using a planarized moth-eye structure on glass substrate.

To improve optical properties of organic light-emitting diodes (OLEDs), we developed a planarized moth-eye structure by ultraviolet nanoimprint lithography (UV-NIL). The moth-eye pattern was fabricated on a glass substrate by UV-NIL using AMONIL polymer resin. It contains nanoscaled, cone-shaped, periodic pattern arrays with a 250 nm diameter and a 550 nm pitch. The glass substrate with the moth-eye structure exhibited a 1%-2% improvement in transmittance of visible wavelengths, but it requires a planarized layer with high-refractive-index materials. Photosensitive titanium precursor resin annealed by UV was used to improve the current efficiency by up to 26% versus conventional OLEDs.

Fabrication of TiO2 nano-to-microscale structures using UV nanoimprint lithography.

TiO2-nanoparticle-dispersed resin was prepared to form various nanoscaled structures using UV nanoimprint lithography (UV NIL). This resin-made of TiO2 nanoparticles, a monomer, solvent, and UV initiator-showed variations in refractive index depending on the nanoparticle concentration. TiO2 nano-to-microscale patterns were fabricated on various substrates such as Si wafer and glass, and even on flexible substrates, by using UV NIL, which offers advantages such as low cost, large area, and high throughput. Low-aspect-ratio, high-aspect-ratio, and microconvex patterns were fabricated using the NIL process. The optical properties of the patterns were analyzed using UV-vis spectrophotometry.