• Title/Summary/Keyword: Vacuum Extraction

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A Chemically-driven Top-down Approach for the Formation of High Quality GaN Nanostructure with a Sharp Tip

  • Kim, Je-Hyeong;O, Chung-Seok;Go, Yeong-Ho;Go, Seok-Min;Jo, Yong-Hun
    • Proceedings of the Korean Vacuum Society Conference
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    • 2011.02a
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    • pp.48-48
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    • 2011
  • We have developed a chemically-driven top-down approach using vapor phase HCl to form various GaN nanostructures and successfully demonstrated dislocation-free and strain-relaxed GaN nanostructures without etching damage formed by a selective dissociation method. Our approach overcomes many limitations encountered in previous approaches. There is no need to make a pattern, complicated process, and expensive equipment, but it produces a high-quality nanostructure over a large area at low cost. As far as we know, this is the first time that various types of high-quality GaN nanostructures, such as dot, cone, and rod, could be formed by a chemical method without the use of a mask or pattern, especially on the Ga-polar GaN. It is well known that the Ga-polar GaN is difficult to etch by the common chemical wet etching method because of the chemical stability of GaN. Our chemically driven GaN nanostructures show excellent structure and optical properties. The formed nanostructure had various facets depending on the etching conditions and showed a high crystal quality due to the removal of defects, such as dislocations. These structure properties derived excellent optical performance of the GaN nanostructure. The GaN nanostructure had increased internal and external quantum efficiency due to increased light extraction, reduced strain, and improved crystal quality. The chemically driven GaN nanostructure shows promise in applications such as efficient light-emitting diodes, field emitters, and sensors.

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Enhancement of Light Extraction in White LED by Double Molding (이중 몰딩에 의한 백색 LED의 광추출 효율 향상)

  • Jang, Min-Suk;Kim, Wan-Ho;Kang, Young-Rea;Kim, Ki-Hyun;Song, Sang-Bin;Kim, Jin-Hyuk;Kim, Jae-Pil
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.25 no.10
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    • pp.849-856
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    • 2012
  • Chip on board type white light emitting diode on metal core printed circuit board with high thixotropy silicone is fabricated by vacuum printing encapsulation system. Encapsulant is chosen by taking into account experimental results from differential scanning calorimeter, shearing strength, and optical transmittance. We have observed that radiant flux and package efficacy are increased from 336 mW to 450 mW and from 11.9 lm/W to 36.2 lm/W as single dome diameter is varied from 2.2 mm to 2.8 mm, respectively. Double encapsulation structure with 2.8 mm of dome diameter shows further significant enhancement of radiant flux and package efficacy to 667 mW and 52.4 lm/W, which are 417 mW and 34.8 lm/W at single encapsulation structure, respectively.

Enhanced Si based negative electrodes using RF/DC magnetron sputtering for bulk lithium ion batteries

  • Hwang, Chang-Muk;Park, Jong-Wan
    • Proceedings of the Korean Vacuum Society Conference
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    • 2010.02a
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    • pp.277-277
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    • 2010
  • The capacity of the carbonaceous materials reached ca. $350\;mAhg^{-1}$ which is close to theorestical value of the carbon intercalation composition $LiC_6$, resulting in a relatively low volumetric Li capacity. Notwithstanding the capacities of carbon, it will not adjust well to the need so future devices. Silicon shows the highest gravimetric capacities (up to $4000\;mAhg^{-1}$ for $Li_{21}Si_5$). Although Si is the most promising of the next generation anodes, it undergoes a large volume change during lithium insertion and extraction. It results in pulverization of the Si and loss of electrical contact between the Si and the current collector during the lithiation and delithiation. Thus, its capacity fades rapidly during cycling. We focused on electrode materials in the multiphase form which were composed of two metal compounds to reduce the volume change in material design. A combination of electrochemically amorphous active material in an inert matrix (Si-M) has been investigated for use as negative electrode materials in lithium ion batteries. The matrix composited of Si-M alloys system that; active material (Si)-inactive material (M) with Li; M is a transition metal that does not alloy with Li with Li such as Ti, V or Mo. We fabricated and tested a broad range of Si-M compositions. The electrodes were sputter-deposited on rough Cu foil. Electrochemical, structural, and compositional characterization was performed using various techniques. The structure of Si-M alloys was investigated using X-ray Diffractometer (XRD) and transmission electron microscopy (TEM). Surface morphologies of the electrodes are observed using a field emission scanning electron microscopy (FESEM). The electrochemical properties of the electrodes are studied using the cycling test and electrochemical impedance spectroscopy (EIS). It is found that the capacity is strongly dependent on Si content and cycle retention is also changed according to M contents. It may be beneficial to find materials with high capacity, low irreversible capacity and that do not pulverize, and that combine Si-M to improve capacity retention.

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The diagnosis of Plasma Through RGB Data Using Rough Set Theory

  • Lim, Woo-Yup;Park, Soo-Kyong;Hong, Sang-Jeen
    • Proceedings of the Korean Vacuum Society Conference
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    • 2010.02a
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    • pp.413-413
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    • 2010
  • In semiconductor manufacturing field, all equipments have various sensors to diagnosis the situations of processes. For increasing the accuracy of diagnosis, hundreds of sensors are emplyed. As sensors provide millions of data, the process diagnosis from them are unrealistic. Besides, in some cases, the results from some data which have same conditions are different. We want to find some information, such as data and knowledge, from the data. Nowadays, fault detection and classification (FDC) has been concerned to increasing the yield. Certain faults and no-faults can be classified by various FDC tools. The uncertainty in semiconductor manufacturing, no-faulty in faulty and faulty in no-faulty, has been caused the productivity to decreased. From the uncertainty, the rough set theory is a viable approach for extraction of meaningful knowledge and making predictions. Reduction of data sets, finding hidden data patterns, and generation of decision rules contrasts other approaches such as regression analysis and neural networks. In this research, a RGB sensor was used for diagnosis plasma instead of optical emission spectroscopy (OES). RGB data has just three variables (red, green and blue), while OES data has thousands of variables. RGB data, however, is difficult to analyze by human's eyes. Same outputs in a variable show different outcomes. In other words, RGB data includes the uncertainty. In this research, by rough set theory, decision rules were generated. In decision rules, we could find the hidden data patterns from the uncertainty. RGB sensor can diagnosis the change of plasma condition as over 90% accuracy by the rough set theory. Although we only present a preliminary research result, in this paper, we will continuously develop uncertainty problem solving data mining algorithm for the application of semiconductor process diagnosis.

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Microwave Propagation in the Plasma for 28 GHz Superconducting ECRIS (28 GHz 초전도 ECRIS 플라즈마에서의 마이크로파 전파)

  • Wang, S.J.;Won, M.S.;Lee, B.S.;Kim, S.H.;Kwak, J.G.;Jeong, S.H.;Kim, S.K.;An, C.Y.
    • Journal of the Korean Vacuum Society
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    • v.19 no.6
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    • pp.467-474
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    • 2010
  • Packet propagation and absorption for the 28 GHz superconducting ECRIS under developing by KBSI Pusan center is analyzed with limited parameter range. The microwave power generated by 28 GHz gyrotron is axially injected to the plasma cavity through waveguide system. According to the analytical ray tracing calculation, the wave packet launched quasi-longitudinally at a high magnetic field side changes its direction from outward to inward as it is approaching resonance layer. Therefore, initially diverging wave does not likely hit a conducting surface before absorbing by electron cyclotron resonance. Also, absorption by plasma with moderate electron density is so strong that reflection by an extraction plate may not be expected.

A Simple, Rapid, and Automatic Centrifugal Microfluidic System for Influenza A H1N1 Viral RNA Purification

  • Park, Byung Hyun;Jung, Jae Hwan;Oh, Seung Jun;Seo, Tae Seok
    • Proceedings of the Korean Vacuum Society Conference
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    • 2013.08a
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    • pp.277.1-277.1
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    • 2013
  • Molecular diagnostics consists of three processes, which are a sample pretreatment, a nucleic acid amplification, and an amplicon detection. Among three components, sample pretreatment is an important process in that it can increase the limit of detection by purifying nucleic acid in biological sample from contaminants that may interfere with the downstream genetic analysis such as nucleic acid amplification and detection. To achieve point-of-care virus detection system, the sample pretreatment process needs to be simple, rapid, and automatic. However, the commercial RNA extraction kits such as Rneasy (Qiagen) or MagnaPure (Roche) kit are highly labor-intensive and time-consuming due to numerous manual steps, and so it is not adequate for the on-site sample preparation. Herein, we have developed a rotary microfluidic system to extract and purify the RNA without necessity of external mechanical syringe pumps to allow flow control using microfluidic technology. We designed three reservoirs for sample, washing buffer, and elution buffer which were connected with different dimensional microfluidic channels. By controlling RPM, we could dispense a RNA sample solution, a washing buffer, and an elution buffer successively, so that the RNA was captured in the sol-gel solid phase, purified, and eluted in the downstream. Such a novel rotary sample preparation system eliminates some complicated hardwares and human intervention providing the opportunity to construct a fully integrated genetic analysis microsystem.

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Fabrication of the catalyst free GaN nanorods on Si grown by MOCVD

  • Ko, Suk-Min;Cho, Yong-Hoon
    • Proceedings of the Korean Vacuum Society Conference
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    • 2010.08a
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    • pp.232-232
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    • 2010
  • Recently light emitting diodes (LEDs) have been expected as the new generation light sources because of their advantages such as small size, long lifetime and energy-saving. GaN, as a wide band gap material, is widely used as a material of LEDs and GaN nanorods are the one of the most widely investigated nanostructure which has advantages for the light extraction of LEDs and increasing the active area by making the cylindrical core-shell structure. Lately GaN nanorods are fabricated by various techniques, such as selective area growth, vapor-liquid-solid (VLS) technique. But these techniques have some disadvantages. Selective area growth technique is too complicated and expensive to grow the rods. And in the case of VLS technique, GaN nanorods are not vertically aligned well and the metal catalyst may act as the impurity. So we just tried to grow the GaN nanorods on Si substrate without catalyst to get the vertically well aligned nanorods without impurity. First we deposited the AlN buffer layer on Si substrate which shows more vertical growth mode than sapphire substrate. After the buffer growth, we flew trimethylgallium (TMGa) as the III group source and ammonia as the V group source. And during the GaN growth, we kept the ammonia flow stable and periodically changed the flow rate of TMGa to change the growth mode of the nanorods. Finally, as the optimization, we changed the various growth conditions such as the growth temperature, the working pressure, V/III ratio and the doping level. And we are still in the process to reduce the diameter of the nanorods and to extend the length of the nanorods simultaneously. In this study, we focused on the shape changing of GaN nanorods with different growth conditions. So we confirmed the shape of the nanorods by scanning electron microscope (SEM) and carried out the Photoluminescence (PL) measurement and x-ray diffraction (XRD) to examine the crystal quality difference between samples. Detailed results will be discussed.

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Wet Synthesis of Hydroxylammonium Nitrate (HAN) and Solid Phase Extraction Using Dual Organic Solvents (수산화암모늄나이트레이트(HAN)의 습식합성 및 이중 유기용매를 이용한 고체상 추출)

  • Kim, Sohee;Kwon, Younja;Jeon, Jong-Ki;Jo, Youngmin
    • Applied Chemistry for Engineering
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    • v.31 no.3
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    • pp.317-322
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    • 2020
  • Hydroxylammonium nitrate (HAN; NH3OHNO3) is an ionic energy material having a low melting temperature and vapor pressure with a high oxygen balance. To utilize it as an oxidizer for a high content liquid mono-propellant, a dual solvent was used to obtain HAN in a solid particulate form. The dehydrated crystal from an aqueous HAN was washed with dual organic solvents including acetone and ethanol, finally resulting in the moisture content of 13.8 wt%. When acetone was applied as a single solvent, the maximum synthesis yield of 88%, the HAN content evaluated by TGA of 86.2%, and the decomposition temperature ranged 160℃ to 205℃ were achieved.

Evaluations of Si based ternary anode materials by using RF/DC magnetron sputtering for lithium ion batteries

  • Hwang, Chang-Muk;Park, Jong-Wan
    • Proceedings of the Korean Vacuum Society Conference
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    • 2010.08a
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    • pp.302-303
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    • 2010
  • Generally, the high energy lithium ion batteries depend intimately on the high capacity of electrode materials. For anode materials, the capacity of commercial graphite is unlike to increase much further due to its lower theoretical capacity of 372 mAhg-1. To improve upon graphite-based negative electrode materials for Li-ion rechargeable batteries, alternative anode materials with higher capacity are needed. Therefore, some metal anodes with high theoretic capacity, such as Si, Sn, Ge, Al, and Sb have been studied extensively. This work focuses on ternary Si-M1-M2 composite system, where M1 is Ge that alloys with Li, which has good cyclability and high specific capacity and M2 is Mo that does not alloy with Li. The Si shows the highest gravimetric capacity (up to 4000mAhg-1 for Li21Si5). Although Si is the most promising of the next generation anodes, it undergoes a large volume change during lithium insertion and extraction. It results in pulverization of the Si and loss of electrical contact between the Si and the current collector during the lithiation and delithiation. Thus, its capacity fades rapidly during cycling. Si thin film is more resistant to fracture than bulk Si because the film is firmly attached to the substrate. Thus, Si film could achieve good cycleability as well as high capacity. To improve the cycle performance of Si, Suzuki et al. prepared two components active (Si)-active(Sn, like Ge) elements film by vacuum deposition, where Sn particles dispersed homogeneously in the Si matrix. This film showed excellent rate capability than pure Si thin film. In this work, second element, Ge shows also high capacity (about 2500mAhg-1 for Li21Ge5) and has good cyclability although it undergoes a large volume change likewise Si. But only Ge does not use the anode due to its costs. Therefore, the electrode should be consisted of moderately Ge contents. Third element, Mo is an element that does not alloys with Li such as Co, Cr, Fe, Mn, Ni, V, Zr. In our previous research work, we have fabricated Si-Mo (active-inactive elements) composite negative electrodes by using RF/DC magnetron sputtering method. The electrodes showed excellent cycle characteristics. The Mo-silicide (inert matrix) dispersed homogeneously in the Si matrix and prevents the active material from aggregating. However, the thicker film than $3\;{\mu}m$ with high Mo contents showed poor cycling performance, which was attributed to the internal stress related to thickness. In order to deal with the large volume expansion of Si anode, great efforts were paid on material design. One of the effective ways is to find suitably three-elements (Si-Ge-Mo) contents. In this study, the Si based composites of 45~65 Si at.% and 23~43 Ge at.%, and 12~32 Mo at.% are evaluated the electrochemical characteristics and cycle performances as an anode. Results from six different compositions of Si-Ge-Mo are presented compared to only the Si and Ge negative electrodes.

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Desorption of organic Compounds from the Simulated Soils by Soil Vapor Extraction (인공토양으로부터 토양증기추출법에 의한 유기화합물의 탈착 현상에 관한 실험 연구)

  • 이병환;이종협
    • Journal of Korea Soil Environment Society
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    • v.3 no.2
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    • pp.101-114
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    • 1998
  • Soil vapor extraction (SVE) is known to be an effective process to remove the contaminants from the soils by enhancing the vaporization of organic compounds using forced vapor flows or applying vacuum through soils. Experiments are carried out to investigate the effects of the organic contaminants, types of soils, and water contents on the removal efficiency with operating time. In the study, simulated soils include the glass bead which has no micropore, sand and molecular sieve which has a large volume of micropores. As model organic pollutants, toluene, methyl ethyl ketone, and trichloroethylene are selected. Desorption experiments are conducted by flowing nitrogen gas. Under the experimental conditions, it is found that there are linear relationships between logarithm of removal efficiency and logarithm of number of pore volumes. The number of pore volumes are defined as the total amount of air flow through the soil column divided by the pore volume of soil column. For three organic compounds studied, the removal rate is slow for no water content, while the number of pore volumes for removal of organic compounds are notably reduced for water contents up to 37%. For the removal of dense organic compound, such as trichloroethylene, a large number of pore volumes are needed. Also, the effects of the characteristics of simulated soils on the removal efficiency of organic compounds are studied. After the characterization of soil surface, porosity of soil columns and types of contaminants, the results could provide a basis for the design of SVE process.

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