• Title/Summary/Keyword: Thermal Diode

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Development of Passive Millimeter-wave Security Screening System (수동 밀리미터파 보안 검색 시스템 개발)

  • Yoon, Jin-Seob;Jung, Kyung Kwon;Chae, Yeon-Sik
    • Journal of the Institute of Electronics and Information Engineers
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    • v.53 no.7
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    • pp.138-143
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    • 2016
  • The designed and fabricated millimeter-wave security screening system receives radiation energy from an object and a human body. The imaging system consist of sixteen array antennas, sixteen four-stage LNAs, sixteen detectors, an infrared camera, a CCD camera, reflector, and a focusing lens. This system requires high sensitivity and wide bandwidth to detect the input thermal noise. The LNA module of the system has been measured to have 65.8 dB in average linear gain and 82 GHz~102 GHz in bandwidth to enhance the sensitivity for thermal noise, and to receive it over a wide bandwidth. The detector is used for direct current (DC) output translation of millimeter-wave signals with a zero bias Schottky diode. The lens and front-end of the millimeter-wave sensor are important in the system to detect the input thermal noise signal. The frequency range in the receiving sensitivity of the detectors was 350 to 400 mV/mW at 0 dBm (1 mW) input power. The developed W-band imaging system is effective for detecting and identifying concealed objects such as metal or plastic.

Development on New Laser Tabbing Process for Modulation of Thin Solar Cell (박형 태양 전지 모듈화를 위한 레이져 태빙 자동화 공정(장비) 개발)

  • No, Donghun;Choi, Chul-June;Cho, Hyun Young;Yu, Jae Min;Kim, JungKeun
    • 한국신재생에너지학회:학술대회논문집
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    • 2010.06a
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    • pp.58.1-58.1
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    • 2010
  • In solar cell module manufacturing, single solar cells has to be joined electrically to strings. Copper stripes coated with tin-silver-copper alloy are joined on screen printed silver of solar cells which is called busbar. The bus bar collects the electrons generated in solar cell and it is connected to the next cell in the conventional module manufacturing by a metal stringer using conventional hot air or infrared lamp soldering systems. For thin solar cells, both soldering methods have disadvantages, which heats up the whole cell to high temperatures. Because of the different thermal expansion coefficient, mechanical stresses are induced in the solar cell. Recently, the trend of solar cell is toward thinner thickness below 180um and thus the risk of breakage of solar cells is increasing. This has led to the demand for new joining processes with high productivity and reduced error rates. In our project, we have developed a new method to solder solar cells with a laser heating source. The soldering process using diode laser with wavelength of 980nm was examined. The diode laser used has a maximum power of 60W and a scanner system is used to solder dimension of 6" solar cell and the beam travel speed is optimized. For clamping copper stripe to solar cell, zirconia(ZrO)coated iron pin-spring system is used to clamp both joining parts during a scanner system is traveled. The hot plate temperature that solar cell is positioned during lasersoldering process is optimized. Also, conventional solder joints after $180^{\circ}C$ peel tests are compared to the laser soldering methods. Microstructures in welded zone shows that the diffusion zone between solar cell and metal stripes is better formed than inIR soldering method. It is analyzed that the laser solder joints show no damages to the silicon wafer and no cracks beneath the contact. Peel strength between 4N and 5N are measured, with much shorter joining time than IR solder joints and it is shown that the use of laser soldering reduced the degree of bending of solar cell much less than IR soldering.

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CFD analysis for effects of the crucible geometry on melt convection and growth behavior during sapphire single crystal growth by Kyropoulos process (사파이어 단결정의 Kyropoulos 성장시 도가니 형상에 따른 유동장 및 결정성장 거동의 CFD 해석)

  • Ryu, J.H.;Lee, W.J.;Lee, Y.C.;Jo, H.H.;Park, Y.H.
    • Journal of the Korean Crystal Growth and Crystal Technology
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    • v.22 no.3
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    • pp.115-121
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    • 2012
  • Sapphire single crystals have been highlighted for epitaxial gallium nitride films in high-power laser and light emitting diode (LED) industries. Among the many crystal growth methods, the Kyropoulos process is an excellent commercial method for growing larger, high-optical-quality sapphire crystals with fewer defects. Because the properties and growth behavior of sapphire crystals are influenced largely by the temperature distribution and convection of molten sapphire during the manufacturing process, accurate predictions of the thermal fields and melt flow behavior are essential to design and optimize the Kyropoulos crystal growth process. In this study, computational fluid dynamic simulations were performed to examine the effects of the crucible geometry aspect ratio on melt convection during Kyropoulos sapphire crystal growth. The results through the evolution of various growth parameters on the temperature and velocity fields and convexity of the crystallization interface based on finite volume element simulations show that lower aspect ratio of the crucible geometry can be helpful for the quality of sapphire single crystal.

The Study of Ag Thin Film of Suitable Anode for T-OLED: Focused on Nanotribology Methode (UV 처리에 의한 T-OLED용 산화전극에 적합한 Ag 박막연구: Nano-Mechanics 특성 분석을 중심으로)

  • Lee, Kyu Young;Kim, Soo In;Kim, Joo Young;Kwon, Ku Eun;Kang, Yong Wook;Son, Ji Won;Jeon, Jin Woong;Kim, Min Chul;Lee, Chang Woo
    • Journal of the Korean Vacuum Society
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    • v.21 no.6
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    • pp.328-332
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    • 2012
  • The work function of Ag (silver) is too low (~4.3 eV) to be used as an electrode of T-OLED (Top Emission Organic Light Emitting Diode). To solve this weakness, researches used plasma-, UV-, or thermal treatment on Ag films in order to increase the work function (~5.0 eV). So, most of studies have focused only on the work function of various treated Ag films, but studies focusing on nanomechanical properties were very important to investigate the efficiency and life time of T-OLED etc. In this paper, we focused on the mechanical properties of the Ag and $AgO_x$ film. The Ag was deposited on a glass substrate with the thickness of 150 nm by using rf-magnetron sputter with the power was fixed at 100 W and working pressure was 3 mTorr. The deposited Ag film was UV treated by UV lamp for several minutes (0~9 min). We measured the sheet resistance and mechanical property of the deposited film. From the experimental result, there were some differences of the sheet resistance and surface hardness of Ag thin film between short time (0~3 min) and long time UV treatment. These result presumed that the induced stress was taken place by the surface oxidation after UV treatment.

Characteristics of Nickel_Titanium Dual-Metal Schottky Contacts Formed by Over-Etching of Field Oxide on Ni/4H-SiC Field Plate Schottky Diode and Improvement of Process (Ni/4H-SiC Field Plate Schottky 다이오드 제작 시 과도 식각에 의해 형성된 Nickel_Titanium 이중 금속 Schottky 접합 특성과 공정 개선 연구)

  • Oh, Myeong-Sook;Lee, Jong-Ho;Kim, Dae-Hwan;Moon, Jeong-Hyun;Yim, Jeong-Hyuk;Lee, Do-Hyun;Kim, Hyeong-Joon
    • Korean Journal of Materials Research
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    • v.19 no.1
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    • pp.28-32
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    • 2009
  • Silicon carbide (SiC) is a promising material for power device applications due to its wide band gap (3.26 eV for 4H-SiC), high critical electric field and excellent thermal conductivity. The Schottky barrier diode is the representative high-power device that is currently available commercially. A field plate edge-terminated 4H-SiC was fabricated using a lift-off process for opening the Schottky contacts. In this case, Ni/Ti dual-metal contacts were unintentionally formed at the edge of the Schottky contacts and resulted in the degradation of the electrical properties of the diodes. The breakdown voltage and Schottky barrier height (SBH, ${\Phi}_B$) was 107 V and 0.67 eV, respectively. To form homogeneous single-metal Ni/4H-SiC Schottky contacts, a deposition and etching method was employed, and the electrical properties of the diodes were improved. The modified SBDs showed enhanced electrical properties, as witnessed by a breakdown voltage of 635 V, a Schottky barrier height of ${\Phi}_B$=1.48 eV, an ideality factor of n=1.04 (close to one), a forward voltage drop of $V_F$=1.6 V, a specific on resistance of $R_{on}=2.1m{\Omega}-cm^2$ and a power loss of $P_L=79.6Wcm^{-2}$.

Low temperature growth of Ga2O3 thin films on Si substrates by MOCVD and their electrical characteristics (MOCVD에 의한 Si 기판 위의 Ga2O3 박막 저온 결정 성장과 전기적 특성)

  • Lee, Jung Bok;Ahn, Nam Jun;Ahn, Hyung Soo;Kim, Kyung Hwa;Yang, Min
    • Journal of the Korean Crystal Growth and Crystal Technology
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    • v.32 no.2
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    • pp.45-50
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    • 2022
  • Ga2O3 thin films were grown on n-type Si substrates at various growth temperatures of 500, 550, 600, 650 and 700℃. The Ga2O3 thin films grown at 500℃ and 550℃ were characterized as featureless flat surface. Grown at higher temperatures (600, 650, and 700℃) showed very rough surface morphology. To figure out the annealing effect on the thin films grown at relatively low temperatures (500, 550, 600, 650 and 700℃), the Ga2O3 films were thermally treated at 900℃ for 10 minutes. Crystal structure of the Ga2O3 films grown at 500 and 550℃ were changed from amorphous to polycrystalline structure with flat surface. Ga2O3 film grown at 550℃ was chosen for the fabrication of a Schottky barrier diode (SBD). Electrical properties of the SBDs depend on the thermal treatment were evaluated. A MSM type photodetector was made on the low temperature grown Ga2O3 thin film. The photocurrent for the illumination of 266 nm wavelength showed 5.32 times higher than dark current at the operating voltage of 10 V.

In-situ Thermally Curable Hyper-branched 10H-butylphenothiazine

  • Jo, Mi-Young;Lim, Youn-Hee;Ahn, Byung-Hyun;Lee, Gun-Dae;Kim, Joo-Hyun
    • Bulletin of the Korean Chemical Society
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    • v.33 no.2
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    • pp.492-498
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    • 2012
  • A hyper branched 10-butylphenothiazine with in-situ thermally curable methacrylate (1,3,5-tris-[$\{$10-Butyl-3-(4-(2-methyl-acryloyloxy)-phenyl)-7-yl-10H-phenothiazine$\}$]-benzene, (tris-PTMA)) was synthesized successfully. From the TGA thermogram of tris-PTMA was thermally stable up to $336^{\circ}C$. In the first heating scan of DSC thermogram, tris-PTMA showed glass transition temperature (Tg) at $140^{\circ}C$ and broad endothermic process in the region of $144-179^{\circ}C$, which is thermally curing temperature. In the second heating process, $T_g$ exhibited at $158.7^{\circ}C$ and endothermic process was not observed. Thermally cured tris-PTMA showed no big change in the UV-visible spectrum after washing with organic solvent such as methylene chloride, chloroform, toluene, indicating that thermally cured film was very good solvent resistance. Thermally cured tris-PTMA was electrochemically stable and the HOMO energy level of tris-PTMA was -5.54 eV. The maximum luminance efficiency of double layer structured polymer light-emitting diode based on in-situ thermally cured tris-PTMA was 0.685 cd/A at 16.0 V, which was higher than that of the device without thermally cured tris-PTMA (0.348 cd/A at 15.0 V).

Contact Resistance and Leakage Current of GaN Devices with Annealed Ti/Al/Mo/Au Ohmic Contacts

  • Ha, Min-Woo;Choi, Kangmin;Jo, Yoo Jin;Jin, Hyun Soo;Park, Tae Joo
    • JSTS:Journal of Semiconductor Technology and Science
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    • v.16 no.2
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    • pp.179-184
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    • 2016
  • In recent years, the on-resistance, power loss and cell density of Si power devices have not exhibited significant improvements, and performance is approaching the material limits. GaN is considered an attractive material for future high-power applications because of the wide band-gap, large breakdown field, high electron mobility, high switching speed and low on-resistance. Here we report on the Ohmic contact resistance and reverse-bias characteristics of AlGaN/GaN Schottky barrier diodes with and without annealing. Annealing in oxygen at $500^{\circ}C$ resulted in an increase in the breakdown voltage from 641 to 1,172 V for devices with an anode-cathode separation of $20{\mu}m$. However, these annealing conditions also resulted in an increase in the contact resistance of $0.183{\Omega}-mm$, which is attributed to oxidation of the metal contacts. Auger electron spectroscopy revealed diffusion of oxygen and Au into the AlGaN and GaN layers following annealing. The improved reverse-bias characteristics following annealing in oxygen are attributed to passivation of dangling bonds and plasma damage due to interactions between oxygen and GaN/AlGaN. Thermal annealing is therefore useful during the fabrication of high-voltage GaN devices, but the effects on the Ohmic contact resistance should be considered.

Accelerated Degradation Stress of High Power Phosphor Converted LED Package (형광체 변환 고출력 백색 LED 패키지의 가속 열화 스트레스)

  • Chan, Sung-Il;Jang, Joong-Soon
    • Journal of the Microelectronics and Packaging Society
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    • v.17 no.4
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    • pp.19-26
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    • 2010
  • We found that saturated water vapor pressure is the most dominant stress factor for the degradation phenomenon in the package for high-power phosphor-converted white light emitting diode (high power LED). Also, we proved that saturated water vapor pressure is effective acceleration stress of LED package degradation from an acceleration life test. Test conditions were $121^{\circ}C$, 100% R.H., and max. 168 h storage with and without 350 mA. The accelerating tests in both conditions cause optical power loss, reduction of spectrum intensity, device leakage current, and thermal resistance in the package. Also, dark brown color and pore induced by hygro-mechanical stress partially contribute to the degradation of LED package. From these results, we have known that the saturated water vapor pressure stress is adequate as the acceleration stress for shortening life test time of LED packages.

Effect of the low level light irradiation to NTacSam:SD tissue cell culture (NTacSam:SD의 조직세포 배양에 저출력 광원의 효과)

  • Kim, Tae-Gon;Kim, Toung-Pyo;Park, No-Bong;Lee, Ho-Sic;Park, Yong-Pil;Cheon, Min-Woo
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2009.06a
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    • pp.423-423
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    • 2009
  • Currently, lasers are one of the most popular light sources in use for medical treatment. Many studies on low power lasers are being done in cell culture or through animal tests and most report different findings, making it difficult to verify their true effects. There are shifts in trends of studies from laser and LED that are expensive and generate heat problem to LED that are economically effective and safe. Its near infrared rays can penetrate deep into skin or muscle, up to 23 cm, without causing thermal damage or impairing neighboring tissues. This study verified the performance and effectiveness of an LED irradiator that was designed to emit similar wavelengths to that of a laser and thus could be used instead of a low level laser therapy in experiments on animals. And then, each experiment was performed to irradiation group and non-irradiation group for NTacSam:SD tissue cells. MIT assay method was chosen to verify the cell increase of two groups and the effect of irradiation on cell proliferation was examined by measuring 590nm transmittance of ELISA reader. As a result, the cell increase of NTacSam:SD tissue cells was verified in irradiation group as compared to non-irradiation group. The fact that specific wavelength irradiation has an effect on cell vitality and proliferation is known through this study.

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