Highly ordered wrinkling morphologies of liquid crystalline polymer films are demonstrated based on simple multi-rubbing. The spontaneous pattern formation of periodic wrinkling morphology is achieved through utilizing plasma treatment on a predefined alignment layer. The multi-directional ordering on the alignment layer obtained through selectively covering the alignment layer with a protective layer, which is chemically inert and keeps alignment properties during another rubbing process. The ordering of the wrinkle pattern can be tailored through a molecular orientation of liquid crystal (LC) and a process condition, including film thickness, plasma treatment, and rubbing. The proposed methods enable the spontaneous pattern formation of well-aligned one- or two-dimensionally periodic microstructures over a large area, without an additional template or patterning steps. Since the LC polymer incorporated the optical anisotropic mesogenic groups into polymer chains, it has an optical birefringence in the film and it can be utilized for optical devices requiring a microstructure on a surface.

Feasibility of multiwavelength Raman spectroscopy was studied as a potential in-line monitoring technique for grain size distribution in channel poly-Si used in three dimensional stacked NAND (3D NAND) Flash memory devices. Various channel poly-Si materials in 3D-NAND Flash memory devices, converted from chemical vapor deposition (CVD) grown a-Si, were characterized using non-contact, multiwavelength Raman spectroscopy and high resolution cross-sectional transmission electron microscopy (HRXTEM). The Raman characterization results were compared with HRXTEM images. The correlation between the grain size distribution characterized by multiwavelength Raman spectroscopy and “on current” (ION) of 3D NAND Flash memory devices was investigated. Good correlation between these techniques was seen. Multiwavelength Raman spectroscopy is very promising as a non-destructive in-line monitoring technique for grain size distribution in channel poly-Si used in 3D NAND Flash memory devices.

Background: The influences of demographics, culture, language, and environmental changes on Mini-Mental State Examination (MMSE) scores are considerable.

Methods: Using a sample of 7452 healthy, community-dwelling elderly Koreans, aged 55 to 94 years, who participated in the four ongoing geriatric cohorts in Korea, we investigated demographic influences on MMSE scores and derived normative data for this population. Geropsychiatrists strictly excluded subjects with cognitive disorders according to the protocol of the Korean version of the Consortium to Establish a Registry for Alzheimer's Disease Assessment Packet (CERAD-K) Clinical Assessment Battery (CERAD-K-C).

Results: Education (standardized β = 0.463), age (standardized β = −0.303), and gender (standardized β = −0.057) had significant effects on MMSE scores (p < 0.001). The score of MMSE increase 0.379 point per 1-year education, decrease 0.188 per 1-year older, and decrease 0.491 in women compared to men. Education explained 30.4% of the scores’ total variance, which was much larger than the variances explained by age (8.4%) or gender (0.3%). Accordingly, we present normative data for the MMSE stratified by education (0, 1–3, 4–6, 7–9, 10–12, and ≥ 13 years), age (60–69, 70–79, and 80–89 years), and gender.

Conclusions: We provide contemporary education-, age-, and gender-stratified norms for the MMSE, derived from a large, community-dwelling elderly Korean population sample, which could be useful in evaluating individual MMSE scores.

Anthropogenic land use within watersheds has substantial effects on aquatic habitats and biological communities. From September 2006 to December 2008, we investigated the effects of land use on benthic macroinvertebrate communities by comparing Song Stream and Odae Stream, two adjacent mountain streams in Korea whose watersheds have different land use patterns. Song Stream is significantly disturbed by agricultural activities in the watershed, whereas Odae Stream is relatively undisturbed and is surrounded by a well-conserved forest area. Song Stream had significantly higher levels of all nutrients and sediment-related factors due to the adjacent agricultural area. As a result, Song Stream had markedly lower species community indices, such as taxa richness and abundance. In Song Stream, macroinvertebrate scrapers and predators were most adversely affected, whereas collector-gatherers became a dominant group. Based on correlation and multivariate analyses, total dissolved solids had the strongest negative relationship with macroinvertebrate assemblages, followed by electrical conductivity, total nitrogen, and pH. The proportion of cobble in stream substrate was positively related to the richness and abundance of macroinvertebrates. Our results indicate that disturbances caused by agricultural land use, particularly sand deposition, had significant adverse effects on macroinvertebrate habitats and on the biotic integrity of benthic macroinvertebrate communities.

We report on the basic characteristics and gas sensing operation of density controlled single-walled carbon nanotube (SWCNT) thin films on poly(dimethyl siloxane) (PDMS) substrates The vacuum filteration and PDMS mold transfer method allowed the density of SWCNT distributed to have non-local uniformity. The optical transparency of the SWCNT thin films was inversely proportional to SWCNT density and conductivity. The flexible SWCNT thin film showed high mechanical stability with negligible change in conductance after being bent by 180o. We evaluated its gas sensing operation depending on SWCNT density and bias voltage. It was shown that lower SWCNT density thin films had higher sensitivity to NH3 gas, which may be due to higher exposed surface area for lower density SWCNT thin films. Also, we found that lower bias voltage devices showed faster recovery times. The results show that vacuum filteration and mold transfer method produced flexible SWCNT thin films that have stable mechanical and electrical characteristics and also stable gas sensing capabilities making them applicable to future flexible integrated sensors.

A new post annealing method employing excimer laser pulses is proposed to improve the transfer characteristics and the breakdown voltage of the unpassivated AlGaN/GaN heterostructure field-effect transistor (HFET) and the passivated one. The XeCl excimer laser pulses with wavelength of 308 nm anneal the AlGaN/GaN HFET after the Schottky gate metallization. The interface defects between the Schottky gate metal and a GaN layer is decreased by the lateral heat diffusion of the laser pulses. Our experimental results show that the drain current and the maximum transconductance of the unpassivated AlGaN/GaN HFET after laser pulses annealing are 496 mA/mm and 134 mS/mm while a virgin device shows 434 mA/mm and 113 mS/mm, respectively. The proposed method anneals effectively the SiO2 passivated AlGaN/GaN HFET and the leakage current of the passivated device is decreased from 483 nA to 29 nA.

Selective nucleation and lateral growing method have been developed for high quality ferroelectric PZT(65/35) thin films using perovskite-phase PZT island seed. The PZT films on PZT seed island were transformed into the perovskite phase at temperatures as low as 540°C, which is 150°C lower than compared to that of PZT thin films deposited on Pt films. The temperature difference enables lateral growth without undesirable random nucleation. Maximum grain sizes of the perovskite-phase PZT films were determined by the annealing temperature. The PZT thin films show a leakage current density of 8×10−8 A/cm2, breakdown field of 1240 kV/cm, saturation polarization of 42 μC/cm2, and remanent polarization of 30 μC/cm2, whose values were maintained up to 2×1011 cycles. In this study, we show that when there was no grain boundary in the area measured, degradation such as fatigue and retention was not observed even with Pt electrodes. So the main source of degradation is the grain boundary in the PZT thin films.

The effects of grain boundaries on the characteristics of the PZT thin films using single-grained PZT array by selective nucleation and growth method were investigated by locating the upper Pt electrode of 8 μm× 8 μm sized square directly on the single grains, 1 grain boundary and 4 grain boundaries in a controlled manner. It turned out that when there was no grain boundary, the best ferroelectric and electrical performance were obtained as expected. However, serious degradation was observed in polarization, leakage current, breakdown field and fatigue characteristics when grain boundary was contained in the area measured. This is the first qualitative investigation about the effects of the grain boundaries on the ferroelectric and electrical performance of the PZT thin films. It was found that degradation of the PZT thin films was accelerated with increasing the length of the grain boundaries within the top electrode and the main source of degradation in PZT thin films is grain boundary.

Monoclinic gallium oxide (β-Ga2O3) nanowires were catalytically synthesized by electric arc discharge of GaN powders mixed with a small amount (less than 5 %) of transition metals under a pressure of 500 Torr (80 %-Ar + 20 %-O2). Scanning electron microscope (SEM) and high-resolution transmission electron microscope (HRTEM) images showed that the average diameter of the wires were about 30 nm and their lengths were as long as up to one hundred micrometer, resulting in extremely large aspect ratio. Fourier diffractogram was indicative of single crystalline nature of the β-Ga2O3 wire. HRTEM image also showed β-Ga2O3 with twin defects at the center of the wire which might play as nucleation seeds. Both X-ray diffraction (XRD) patterns and FT-Raman spectra of the wires identified the observed nanowires as monoclinic crystalline gallium oxides.

Light soaking gives rise to the increase of active acceptors as well as to the creation of dangling bonds in boron doped hydrogenated amorphous silicon. The annealing out of the metastable active dopants is slow compared with that of the created dangling bonds, results in higher conductivity than annealed value during heating the sample upon light soaking. The activation energy of the relaxation time for the metastable active dopants is ˜0.1 eV higher than that for the annealing of the created dangling bonds. We ropose a new model to explain our results.

Light-induced changes in vibrational absorption of SiHn have been studied for a-Si:H films. The stretching mode absorption near 2000 cm−1 decreases after light exposure. The magnitude of the change increases as the substrate temperature is lowered, and little change is observed for a-Si:H films deposited above 200°C. From the changes both for the peak and the spectrum, it is suggested that the hydrogen in the bulk diffuses to the microvoids, where it can combine to form H2 in low substrate temperature sample. The B-H modes increase after light soaking, Which is related with the increase in doping efficiency of boron, which is confirmed from the conductivity change with time during illumination.