• Applied Chemistry for Engineering
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• v.34 no.4
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• pp.383-387
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• 2023

The quartz crystal microbalance (QCM), commonly used in high vacuum deposition, becomes difficult to use when a thick film is deposited on the quartz, affecting the crystal's inherent vibration. In this study, a non-destructive optical measurement method was developed to measure the film's deposition rate during the in-situ film deposition process. By measuring the scattered laser intensity caused by the dimer in the parylene gas passing through the gas flow path, it was successfully confirmed that the ratio of the dimer in the parylene gas increases as the pyrolysis temperature decreases. Additionally, it was noted that the film's thickness and haze increase as the pyrolysis temperature decreases by confirming the characteristics of the visible parylene films. Through the research results, we aim to utilize the stable in-situ film deposition rate measurement system to control the precise film deposition rate of parylene films.

• Journal of the Korean Chemical Society
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• v.48 no.4
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• pp.351-357
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• 2004

We have investigated the intensity of Cu 510.6 nm emission line in see-through hollow cathode glow discharge (st-HCGD) for the development of medical Cu vapor laser. In order to acquire the stable plasma in st-HCGD cell at high current, several factors such as current, the length and the inner diameter of cathode tube, the shape of the tube, and the range of the sputtering range were tested. An optimum condition in our st-HCGD cell was obtained at 600 V, 700 mA, 2.3 Torr of Ar gas (100 SCCM), and 40 mm of tube with 4-11-4 mm type cathode design. Also, it was indirectly observed that temperature in the cell could reach more than $1,000{\circ}C$ since Cu cathode was melt at the current more than 700 mA (melting point of Cu, $1084{\circ}C$).

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.06a
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• pp.23-23
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• 2009

GaN-based nitride semiconductors have attracted considerable attention in high-brightness light-emitting-diodes (LEDs) and laser diodes (LDs) covering from green to ultraviolet spectral range. LED and LD heterostructures are usually grown on (0001)-$Al_2O_3$. The large lattice mismatch between $Al_2O_3$ substrates and the GaN layers leads to a high density of defects(dislocations and stacking faults). Moreover, Ga and N atoms are arranged along the polar [0001] crystallographic direction, which leads to spontaneous polarization. In addition, in the InGaN/GaN MQWs heterostructures, stress applied along the same axis can also give rise to piezoelectric polarization. The total polarization, which is the sum of spontaneous and piezoelectric polarizations, is aligned along the [0001] direction of the wurtzite heterostructures. The change in the total polarization across the heterolayers results in high interface charge densities and spatial separation of the electron and hole wave functions, redshifting the photoluminescence peak and decreasing the peak intensity. The effect of polarization charges in the GaN-based heterostructures can be eliminated by growing along the non-polar [$11\bar{2}0$] (a-axis) or [$1\bar{1}00$] (m-axis) orientation instead of thecommonly used polar [0001] (c-axis). For non-polar GaN growth on non-polar substrates, the GaN films have high density of planar defects (basal stacking fault BSFs, prismatic stacking fault PSFs), because the SFs are formed on the basal plane (c-plane) due to their low formation energy. A significant reduction in defect density was recently achieved by applying blocking layer such as SiN, AlN, and AlGaN in non-polar GaN. In this work, we were performed systematic studies of the defects in the nonpolar GaN by conventional and high-resolution transmission electron microscopy.

• Polymer(Korea)
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• v.30 no.3
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• pp.271-278
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• 2006

In order to investigate the structure and dynamics of atatic poly (vinyl alcohol) (PVA)/water system, laser light scattering experiment has been done in the semi-dilute concentration regime at $25^{\circ}C$. The scattering intensity I(q) can be analyzed with the fractal equation of $I(q){\sim}q^{-m}$ instead of Onstein-Zernike type equation. The fractal dimensionality m was found to be constant after reaching the plateau value of $m=2.6{\pm}0.3$ above C=3wt%. The time correlation function of dynamic light scattering has always two different modes such as fast mode and slow one. The cooperative diffusion of fast mode showed concentration independence contrary 4o the reptation theory's concentration dependent exponent of 3/4. The slow mode can be interpreted as the motion of large scale heterogeneities and its strong concentration dependence is apparent with a large negative exponent of -3.0. It is considered that the stereo-regular arrangement with four successive meso units of -OH plays as a key role in forming such heterogeneity.

• 한국정보디스플레이학회:학술대회논문집
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• 2006.08a
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• pp.421-421
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• 2006

The light and energy-efficiency of classical liquid crystal displays is notoriously poor due to the use of absorption-based linear polarisers and colour filters. For instance, the light efficiency of PVAL polarisers is typically between 40 and 45 % and the colour filters have a typical efficiency below 35 % which results in a total light and energy-efficiency of the display below 10 %. In the past, a variety of polarizers were developed with an enhanced efficiency in generating linearly polarized light. Typically, these polarizers are based on the polarisationselective reflection, scattering or refraction of light i.e. one polarisation direction of light is directly transmitted to the LCD/viewer and the other polarization direction of light is depolarised and recycled which results in a typical efficiency for generating linearly polarized light of 70-85 %. Also, special colour filters have been proposed based on chiral-nematic reactive mesogens which increase the efficiency of generating colour. Despite the enormous progress in this field, a need persists for improved methods for generating polarized light and colour based on low cost optical components with a high efficiency. Here, the use of holographic phase gratings is reported for the generation of polarized light and colour. The phase grating are recorded in a photopolymer which is coated onto a backor frontlight for LCDs. Typically the recording is performed in the transmisson mode or in the waveguiding mode and slanted phase gratings are generated with their refractive index modulation at an angle between 20o and 45o with the normal of the substrate. It is shown that phase gratings with a high refractive index modulation and a high efficiency can be generated by a proper selection of the photopolymer and illumination conditions. These phase gratings coupleout linearly polarized light with a high contrast (> 100) and the light is directed directly to the LCD/viewer without the need for redirection foils. Dependent on the type of phase grating, the different colours are coupled-out at a slightly different angle which potentially increases the efficiency of classical colour filters. Moreover, the phase gratings are completely transparent in direct view which opens the possibility to use them in frontlights for LCDs. Holographic polarization gratings posses a periodic pattern in the polarization state of light (and not in the intensity of light). A periodic pattern in the polarization direction of linearly polarized light is obtained upon interference of two circularly polarized laser beams. In the second part of the lecture, it is shown that these periodic polarization patterns can be recorded in a linear photo-polymerizable polymer (LPP) and that such an alignment layer induces a period rotation in the director of (reactive and non-reactive) liquid crystals. By a proper design, optical components can be produced with only first order diffraction and with a very high efficiency (>0.98). It is shown that these diffraction gratings are potentially useful in projection displays with a high brightness and energy efficiency

• KOREAN JOURNAL OF CROP SCIENCE
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• v.59 no.3
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• pp.252-262
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• 2014

Sorghum seed is traditionally used as secondary food sources in addition to rice in Korea. While the hypoglycemia regulating phytochemicals have been found in sorghum seed, peptides related with hypoglycemia never been studied before. To obtain the peptide characteristics and the specifically high-expressed peptides in hypoglycemic sorghum seed, peptide profiles of seven hypoglycemic and five non-hypoglycemic sorghum lines bred in RDA were determined using surface-enhanced laser desorption/ionization time-of-flight mass spectrometry (SELDI-TOF MS). The twelve sorghum lines exhibited 104 peptides on CM10 protein chip array (weak cation exchange) and 95 peptides on Q10 (weak cation exchange) in the molecular mass range from 2,000 to 20,000 Da. Heat map via supervised hierarchical clustering of the significantly different peptides (p < 0.01) in peak intensity among the 12 lines effectively revealed the specifically upregulated peptides in each line and distinguished between 7 hypoglycemic and 5 non-hypoglycemic lines. Through the comparison with hypoglycemic and non-hypoglycemic lines, 10 peptides including 2231.6, 2845.4, 2907.9, 3063.5, 3132.6, 3520.8, 4078.8, 5066.2, 5296.5, 5375.5 Da were specifically high-expressed in hypoglycemic lines at p < 0.00001. This study characterized seed peptides of 12 sorghums and found ten peptides highly expressed for hypoglycemic sorghum lines, which could be used as peptide biomarkers for identification of hypoglycemic sorghum.

• Journal of radiological science and technology
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• v.28 no.4
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• pp.267-272
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• 2005

The effects of As addition in amorphous selenium (a-Se) films for digital X-ray conversion material have been studied using the moving photocarrier grating (MPG) technique. This method utilizes the moving interference pattern generated by the superposition of the two frequency shifted laser beams for the illumination of the sample. This moving intensity grating induces a short circuit current, jsc in a-Se:As film. The transport parameters of the sample are extracted from the grating-velocity dependent short circuit current induced in the sample along the modulation direction. The electron and hole mobility, and recombination lifetime of a-Se films with arsenic (As) additions have been obtained. We have found an increase in hole drift mobility and recombination lifetime, especially when 0.3% As is added into a-Se film, whereas electron mobility decreases with As addition due to the defect density. The transport properties for As doped a-Se films obtained by using MPG technique have been compared with X-ray sensitivity for a-Se:As device. The fabricated a-Se(0.3% As) device film exhibited the highest X-ray sensitivity out of 5 samples.

• Journal of the Korea institute for structural maintenance and inspection
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• v.21 no.6
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• pp.140-146
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• 2017

It is laser induced breakdown spectroscopy(LIBS) that enables qualitative and quantitative analysis of the elements contained in unknown specimen by comparing the wavelength characteristics of each element obtained from the spectral analysis of the standard specimen with the wavelength analysis results from unknown specimens. In this study, the applicability of LIBS to the analysis of major deterioration factors affecting concrete durability was experimentally analyzed. That is, the possibility of applying LIBS to the diagnosis of concrete deterioration by studying the quantitative detection of harmful deteriorating factors on chloride, sulfate and carbonated mortar specimens using LIBS was studied. As a result of LIBS test for each chloride and sulfate specimen, the LIBS spectral wavelength intensity of chlorine and sulfur ions increased linearly with increasing concentration. Carbon ion LIBS spectral wave intensities of carbonated specimens increased nonlinearly over the duration of carbonation exposure. From the above results, it can be partially confirmed that LIBS can be applied to the diagnosis of concrete deterioration. In case of concrete carbonation, it is presumed that carbon content is contained in the cement itself and is different from the detection of chloride and sulfate specimen. Therefore, it is considered that more various parameter studies should be performed to apply LIBS to concrete carbonation.

• Journal of the Society of Cosmetic Scientists of Korea
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• v.36 no.3
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• pp.215-219
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• 2010

In this study, we investigated effects of Monegy (mixture of Sophorae Radix, Panax ginseng, Salvia miltiorrhiza BUNGE) on epilate-induced hair-loss in dorsal region of C57/BL6 mice and external structure of human hair. For morphological and histological analysis in scalp of epilate-induced hair-loss animal model, we utilized several microscopic techniques, such as confocal laser scanning microscopy (CLSM) and LAS 4000. Confocal analysis showed the distribution of FITC-conjugated Monegy and penetration depth compared with normal and control group. Furthermore, when Monegy was topically administrated onto a C57BL6 mouse, it penetrated very well. The fluorescence intensity was increased upto 205 and 113 folds compared to normal and control group, respectively. Also, area of fluorescence was increased to upto 255 to 127 folds compared to normal and control group. Broad scale area of fluorescence in dermis region was observed in the Monegy-treated mice. Furthermore, Monegy induced upto 75% hair repair against depilation. It might be promoted via the induction of growth factors in hair follicle.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• v.9 no.1
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• pp.1022-1025
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• 2005

The effect of substrate surface to the formation of ZnO nanostructures has been investigated using Si (111), $Al_2O_3$(C-plane) $Al_2O_3$(A-plane), and $Al_2O_3$(R-plane) substrates. The growth temperature was controlled from 500$^{\circ}C$ ${\sim}$ 600$^{\circ}C$, and the luminescence properties were investigated by a series of photoluminescence (PL) measurements at the elevating temperatures. ZnO nanostructures grown on Si substrate show strong UV emission intensity along with green emission positioned at 3.22 eV and 2.5 eV, respectively. However, green emission was not observed from the ZnO nanostructures grown on $Al_2O_3$ substrates. It is explained in terms of the difference of the surface energy between Si and $Al_2O_3$. Also, the origin of UV emissions has been discussed by using the temperature-dependent PL. The distinction of the PL spectra is interpreted in terms of the difference of the impurity included in the nanostructures.