• Journal of the Korean Ceramic Society
• /
• v.24 no.2
• /
• pp.170-178
• /
• 1987

Changes of the properties of PECVD-SiN film with the variation of deposition process parameters were investigated and optimum process parameters were determined. The refractive index of the film increased with increasing substrate temperature and pressure, and decreasing rf-power, NH3/SiH4 gas ratio and total gas flow. BHF etch rate and deposition rate show a decreasing tendency with increasing refractive index. The step coverage of the film was not affected much by deposition rate and pressure, but improved apparently with increasing rf-power and NH3/SiH4 gas ratio. Also the optimum process parameters were determined by considering the characteristic properties as well as thickness uniformity of films. The refractive index of the film deposited under this condition was 2.06.

• Journal of Korean Ophthalmic Optics Society
• /
• v.14 no.1
• /
• pp.63-68
• /
• 2009

Purpose: TiN films were deposited on sus304 by unbalanced magnetron sputtering system which was designed and developed as unbalancing the strength of the magnets in the magnetron electrode. The effect of oxygen incorporation in the fabrication of deposited films was investigated. Methods: The cross sections of deposited films on Silicon wafer were observed by SEM to measure the thickness of the films, the components of the surface of the films were identified by XPS survey spectra, the compositional depth-profile of deposited films was examined by an XPS apparatus. Results: From the data of XPS depth profile of films, it could be seen that the element O as well as the elements Ti and N present in the surface of the film and the relative percentage of the element O was constant at 65 at.% with respect to the depth of film. Conclusions: The color change with thickness of the films had something to do with the change of Ti $ 2p_{3/2}$ peak intensity and shape mixed of $ TiO_2$, TiN, $ TiO_{x}N_{y}$ compound.

• Journal of Korea Multimedia Society
• /
• v.6 no.2
• /
• pp.325-331
• /
• 2003

In this paper, we designed a spiral inductor and voltage controlled oscillator with the negative resistor for the bluetooth receiver by using 0.25$\mu\textrm{m}$ 1-poly 5-metal CMOS n-well process. The proposed inductor, which applies multi layer metal structure, is a structure that decreases resistance value by increasing he metal thickness. As the resistance value decreases, the quality factor Q has improved. Also, voltage-controlled oscillator is designed applying 1 port negative resistance, and changes its oscillating frequency by varying outside capacitor values. The simulation results show that oscillating frequency is 2.33~2.58GHz changing from 2pF to 14pF, and the oscillator has oscillating power over 0dBm.

• Journal of the Korean Society for Precision Engineering
• /
• v.29 no.2
• /
• pp.170-177
• /
• 2012

A force/torque sensor using carbon fiber plate was designed and developed to make the sensor be able to measure a wide range of multi degree of force and torque. Using carbon fiber plate of 0.3 mm thickness, the sensor was designed and developed, which has a ${\mu}N$ level order of resolution and about 0.01 N ~ 390 N of wide measurement range. The elastic deformation part has a tripod plate structure and strain gauges are attached on the part to detect the force/torque. The coefficient of determination for the sensor is over 0.955 by the calibration experiment so that the linearity of the sensor is confirmed to be good. Also, experiments on applying 0.005 ~ 40 kg (0.05 ~ 390 N) to each axis were implemented and the sensor is proved to be safe under a high load. Finally, to verify the function calculating the direction of load vector, the directions of various load vectors which have the same magnitude but different directions and the directions of the calculated load vectors are compared and analyzed to accord well.

• Journal of the Institute of Electronics and Information Engineers
• /
• v.50 no.2
• /
• pp.91-97
• /
• 2013

Self-heating effects during operation of high current AlGaN/GaN power transistors degrade the current-voltage characteristics. In particular, this problem becomes serious when a low thermal conductivity Si substrate is used. In this work, AlGaN/GaN-on-Si devices were fabricated with various channel widths and Si substrate thicknesses in which the structure dependent self-heating effects were investigated by temperature dependent measurements as well as thermal simulation. Accordingly, a device structure that can effectively dissipate the heat was proposed in order to achieve the maximum current in a multi-channel, large area device. Employing via-holes and common electrodes with a 100 ${\mu}m$ Si substrate thickness improved the current level by 75% reducing the channel temperature by 68%.

• Korean Journal of Remote Sensing
• /
• v.33 no.5_1
• /
• pp.607-615
• /
• 2017

The aerosol optical thickness data retrieved by Moderate Resolution Imaging Spectrometer (MODIS) of Terra & Aqua and Meteorological Imager (MI) of Communication Ocean and Meteorological Satellite (COMS) are analyzed and compared with the measurement data of Aerosol Robotic Network (AERONET) in Northeast Asia. As the result, the aerosol optical thickness retrieved by MODIS and MI were well agreed at ocean region but quite different at cloud edge and barren surface. The reason was that MODIS aerosol optical thickness was retrieved using the visible and infrared channels but MI was retrieved with the visible channel only. Consequentially, the thin cloud be misinterpreted as aerosol by MI and the difference between MODIS and MI aerosol optical thicknesses could be occurred with Normal Distribution Vegetation Index (NDVI) and land surface property. Therefore, the accuracies of clear/cloud region and surface reflectivity are required in order to improve the aerosol optical thickness algorithm by MI.

• Journal of the Korean Solar Energy Society
• /
• v.23 no.1
• /
• pp.1-8
• /
• 2003

Various efforts to combine new high-tech materials with solar system have been progressed nowadays in order to improve the performance of the existing passive solar system. TIM(Transparent Insulation Material) replacing the conventional outer building envelope glazing as well as the wall is good example for this trend. TI integrated wall is a thermal mass wall with a special shaped TIM instead of using typical envelope materials The tested TIM type is a small(diameter 4mm and thickness 50mm) capillary tube of Okalux model and cement brick(density 1500kg/m3). The purpose of this study was to analyze the thermal performance through the actual measurements performed in a test cell. This study was carried out to justify the following issues. 1) the impact of Tl-wall over the temperature variations 2) the impact of mass wall surface absorptance over the transient thermal behavior and 3) the impact of thermal mass wall thickness over the temperature variations. Finally, as results indicated that the peak time of room temperature was shifted about one hour early when absorptance of thermal mass wall changed from 60% to 95% for the 190mm thickness thermal mass wall test case. the temperature difference of both surfaces of thermal mass wall surface showed about $23^{\circ}C$ during a day of March for the 380mm thickness thermal mass wall case. However, the thermal mass wall was over-heated by outside temperature and solar radiation in a day of May the temperature difference of both surfaces of thermal mass wall surface was indicated $10^{\circ}C$ and inside temperature was observed more than average 22C.

• Journal of Genetic Medicine
• /
• v.11 no.2
• /
• pp.56-62
• /
• 2014

Purpose: To assess the outcomes of increased fetal nuchal translucency (NT), to aid in prenatal counseling and management in our practice. Materials and Methods: We retrospectively reviewed the medical records of patients who underwent first trimester fetal karyotyping using chorionic villi sampling (CVS) and second trimester level II sonography for a fetal NT thickness ${\geq}3.0mm$ between 11 weeks and 13 weeks 6 days' gestation, at Gyeongsang National University Hospital. Pediatric medical records and a telephone interview were used to follow-up live-born children. Exclusion criteria included incomplete data and CVS for other indications. Results: Seventy cases met the inclusion criteria (median NT thickness, 4.7 mm; range, 3.0-16.1 mm). Twenty-nine cases (41.4%) were aneuploid. The prevalence of chromosomal defects increased with NT thickness: NT 3.0-3.4 mm, 16.7%; NT 3.5-4.4 mm, 27.3%; NT 4.5-5.4 mm, 66.7%; NT 5.5-6.4 mm, 37.5%; NT ${\geq}6.5mm$, 62.5%. The most common karyotype abnormality was trisomy 18 (n=12), followed by trisomy 21 (n=9). In chromosomally normal fetuses (n=41), fetal death occurred in 2 cases (4.9%), and structural malformations were found in 11 cases (26.8%). In chromosomally and anatomically normal fetuses (n=28), one child had neurodevelopmental delay (3.6%). Twenty-eight infants who had a prenatal increased NT were alive and well at follow-up (40%). Conclusion: Outcomes of increased fetal NT might help inform prenatal counseling and management. The high prevalence of chromosomal defects associated with increased fetal NT implies that CVS should be performed in the first trimester, particularly considering the stress associated with an uncertain diagnosis.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2010.03a
• /
• pp.16-16
• /
• 2010

GaN-based light-emitting diodes (LEDs) are attracting great interest as candidates for next-generation solid-state lighting, because of their long lifetime, small size, high efficacy, and low energy consumption. However, for general illumination applications, the external quantum efficiency of LEDs, determined by the internal quantum efficiency (IQE) and the light extraction efficiency, must be further increased. The IQE is determined by crystal quality and epitaxial layer structure and high value of IQE more than 70% for blue LEDs have been already reported. However, there is much room for improvement of light extraction efficiency because most of the generated photons from active layer remain inside LEDs by total internal reflection at the interface of semiconductor with air due to the high refractive index difference between LEDs epilayer (for GaN, n=2.5) and air (n=1). The light confining in LEDs will be reabsorbed by the metal electrode or active layer, reducing the efficacy of LEDs. Here, we present the first demonstration of enhanced light extraction by forming a MgO nano-pyramids structure on the surface of vertical-LEDs. The MgO nano-pyramids structure was successfully fabricated at room temperature using conventional electron-beam evaporation without any additional process. The nano-sized pyramids of MgO are formed on the surface during growth due to anisotropic characteristics between (111) and (200) plane of MgO. The ZnO layer with quarter-wavelength in thickness is inserted between GaN and MgO layers to increase the critical angle for total internal reflection, because the refractive index of ZnO (n=1.94) could be matched between GaN (n=2.5) and MgO (n=1.73). The MgO nano-pyramids structure and ZnO refractive-index modulation layer enhanced the light extraction efficiency ofV-LEDs with by 49%, comparing with the V-LEDs with a flat n-GaN surface. The angular-dependent emission intensity shows the enhanced light extraction through the side walls of V-LEDs as well as through the top surface of the n-GaN, because of the increase in critical angle for total internal reflection as well as light scattering at the MgO nano-pyramids surface.

• Korean Journal of Materials Research
• /
• v.16 no.3
• /
• pp.151-156
• /
• 2006

A method for fabrication of nano-scale GaN structure by inductively coupled plasma etching is proposed, exploiting a thermal dewetting of Pt thin film as an etch mask. The nano-scale Pt metal islands were formed by the dewetting of 2-dimensional film on $SiO_2$ dielectric materials during rapid thermal annealing process. For the case of 30 nm thick Pt films, pattern formation and dewetting was initiated at temperatures greater $600^{\circ}C$. Controlling the annealing temperature and time as well as the thickness of the Pt metal film affected the size and density of Pt islands. The activation energy for the formation of Pt metal island was calculated to be 23.2 KJ/mole. The islands show good resistance to dry etching by a $CF_4$ based plasma for dielectric etching indicating that the metal islands produced by dewetting are suitable for use as an etch mask in the fabrication of nano-scale structures.