Using UV nanoimprint lithography(UV-NIL), 1-dimensional(1-D) pattern structures were fabricated on a hybrid mixture thin film of lanthanum oxide and a UV-curable resin. 1-D pattern on a wafer fabricated by the laser interference lithography was transferred to polydimethylsiloxane and this is used as a mold of UV-NIL process. Conducting an X-ray photoelectron spectroscopy, C 1s and La 3d spectra were analyzed, and it was confirmed that hybrid thin film was successfully deposited on glass substrate. Also, transferred pattern structure was observed by using an atomic force microscopy. Through this, it was revealed that agglomerations between 1-D pattern were increased as UV irradiation time increased and this phenomenon disrupted the quality of NIL process. Additionally, liquid crystal(LC) cells with patterned hybrid thin films were fabricated and LC alignment performances were investigated. Using the polarizing optical microscopy and the crystal rotation method, LC alignment state and pretilt angles were observed. Consequently, the uniform homogeneous LC alignment was achieved at UV irradiation time of 1min and 3min where high resolution pattern transfer was observed.
Ultraviolet (UV) light emitting diodes (LEDs) were grown on a patterned n-type GaN substrate (PNS) with 200 nm silicon-di-oxide (SiO2) nano pattern diameter to improve the light output efficiency of the diodes. Wet etched self assembled indium tin oxide (ITO) nano clusters serve as a dry etching mask for converting the SiO2 layer grown on the n-GaN template into SiO2 nano patterns by inductively coupled plasma etching. PNS is obtained by n-GaN regrowth on the SiO2 nano patterns and UV-LEDs were fabricated using PNS as a template. Two UV-LEDs, a reference LED without PNS and a 200 nm PNS UV-LEDs were fabricated. Scanning Electron microscopy (SEM), Transmission Electron Microscopy (TEM), X-Ray Diffraction (XRD), Photoluminescence (PL) and Light output intensity- Input current- Voltage (L-I-V) characteristics were used to evaluate the ITO-SiO2 nanopattern surface morphology, threading dislocation propagation, PNS crystalline property, PNS optical property and UVLED device performance respectively. The light out put intensity was enhanced by 1.6times@100mA for the LED grown on PNS compared to the reference LED with out PNS.
There have been many efforts to modify and improve the properties of functional thin films by hybridization with nano-sized materials. For the fabrication of electronic circuits, micro-patterning is a commonly used process. For photochemical metal-organic deposition, photoresist and dry etching are not necessary for microscale patterning. We obtained direct-patternable SnO2 thin films using a photosensitive solution containing Ag nanoparticles and/or multi-wall carbon nanotubes (MWNTs). The optical transmittance of direct-patternable SnO2 thin films decreased with introduction of nanomaterials due to optical absorption and optical scattering by Ag nanoparticles and MWNTs, respectively. The crystallinity of the SnO2 thin films was not much affected by an incorporation of Ag nanoparticles and MWNTs. In the case of mixed incorporation with Ag nanoparticles and MWNTs, the sheet resistance of SnO2 thin films decreased relative to incorporation of either single component. Valence band spectral analyses of the nano-hybridized SnO2 thin films showed a relation between band structural change and electrical resistance. Direct-patterning of SnO2 hybrid films with a line-width of 30 μm was successfully performed without photoresist or dry etching. These results suggest that a micro-patterned system can be simply fabricated, and the electrical properties of SnO2 films can be improved by incorporating Ag nanoparticles and MWNTs.