• Title/Summary/Keyword: Ga source

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Investigation of Device Characteristics on the Mechanical Film Stress of Contact Etch Stop Layer in Nano-Scale CMOSFET (Nano-Scale CMOSFET에서 Contact Etch Stop Layer의 Mechanical Film Stress에 대한 소자특성 분석)

  • Na, Min-Ki;Han, In-Shik;Choi, Won-Ho;Kwon, Hyuk-Min;Ji, Hee-Hwan;Park, Sung-Hyung;Lee, Ga-Won;Lee, Hi-Deok
    • Journal of the Institute of Electronics Engineers of Korea SD
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    • v.45 no.4
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    • pp.57-63
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    • 2008
  • In this paper, the dependence of MOSFET performance on the channel stress is characterized in depth. The tensile and compressive stresses are applied to CMOSFET using a nitride film which is used for the contact etch stop layer (CESL). Drain current of NMOS and PMOS is increased by inducing tensile and compressive stress, respectively, due to the increased mobility as well known. In case of NMOS with tensile stress, both decrease of the back scattering ratio ($\tau_{sat}$) and increase of the thermal injection velocity ($V_{inj}$) contribute the increase of mobility. It is also shown that the decrease of the $\tau_{sat}$ is due to the decrease of the mean free path ($\lambda_O$). On the other hand, the mobility improvement of PMOS with compressive stress is analyzed to be only due to the so increased $V_{inj}$ because the back scattering ratio is increased by the compressive stress. Therefore it was confirmed that the device performance has a strong dependency on the channel back scattering of the inversion layer and thermal injection velocity at the source side and NMOS and PMOS have different dependency on them.

Characterization of carbon microspheres grown by HVPE (HVPE 방법에 의해 성장된 탄소 마이크로구의 특성)

  • Lee, Chanmi;Jeon, Hunsoo;Park, Minah;Lee, Chanbin;Yang, Min;Yi, Sam Nyung;Ahn, Hyung Soo;Kim, Suck-Whan;Yu, Young Moon;Shin, Keesam;Bae, Jong Seong;Lee, Hyo Suk;Sawaki, Nobuhiko
    • Journal of the Korean Crystal Growth and Crystal Technology
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    • v.25 no.2
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    • pp.62-67
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    • 2015
  • The carbon microspheres of a core-shell type were grown by the method of mixed-source hydride vapor phase epitaxy (HVPE). The surface and the cross section of the carbon microsphere grown by a new method were observed by scanning electron microscope (SEM). The characteristics of the carbon microsphere were investigated by X-ray photoelectron spectroscopy (XPS) and a high resolution-transmission electron microscope (HR-TEM). From these measurements, the diameters of carbon sphere were about few hundred micrometers. Furthermore, we show that the carbon microsphere of the core-shell type by mixed-source HVPE method can be grown successfully with the larger size than those of the existing one. This mixed-source HVPE method is proposed a new method for making of carbon microsphere.

Seismic Amplitude and Frequency Characteristics of Gas hydrate Bearing Geologic Model (가스 하이드레이트 지층 모델의 탄성파 진폭 및 주파수 특성)

  • Shin, Sung-Ryul;Lee, Sang-Cheol;Park, Keun-Pil;Lee, Ho-Young;Yoo, Dong-Geun;Kim, Young-Jun
    • Geophysics and Geophysical Exploration
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    • v.11 no.2
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    • pp.116-126
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    • 2008
  • In gas hydrate survey, seismic amplitude and frequency characteristics play a very important role in determining whether gas hydrate exists. According to the variation of source frequency and scatterer size, we study seismic amplitude characteristics using elastic modeling applied at staggered grids. Generally speaking, scattering occurs in proportion to the square of source frequency and the scatterer volume, which has an effect on seismic amplitude. The higher source frequency is, the more scattering occurs in gas hydrate bearing zone. Therefore, BSR is hardly observed in high frequencies. On the other side, amplitude blanking zone and BSR is clearly observed in lower frequencies although the resolution is poor as a whole. Seismic reflections traveling through free-gas layer below gas hydrate bearing zone decay so severely a high frequency component that a low frequency term is dominant. Amplitude anomaly of BSR result from high acoustic impedance contrast due to free-gas, which is a very crucial factor to estimate gas hydrate bearing zone. Seismic frequency analysis is carried out using wavelet transform method that frequency component could be decomposed with time variation. In application of wavelet transform to the seismic physical experiments data, we can observe that reflections traveling through air layer, which corresponds to the free-gas layer, decay a high frequency component.

Analysis on Characteristics of Pigments Manufactured with Various Neorok Produced from Mt. Gwangjeongsan, Pohang (포항 광정산 일대 산출 뇌록으로 제조한 안료의 특성 분석)

  • Mun, Seong Woo;Kang, Young Seok;Kim, Ji Sun;Hwang, Ga-Hyun;Park, Ju Hyun;Lee, Sun Myung;Jeong, Hye Young
    • Journal of Conservation Science
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    • v.36 no.6
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    • pp.533-540
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    • 2020
  • Mt. Neoseongsan (NSS) is the only natural Neorok source in Korea. The geological, historical, and cultural values of NSS were recognized in 2013, and NSS has since been designated and maintained as a natural monument (No. 547), which has restricted the research and utilization of NSS Neorok. The limited NSS Neorok supply has hindered the restoration research of traditional pigments. Recently, a large amount of Neorok has been mined from Mt. Gwangeongsan (GJS) and is expected to be the main supply source of Neorok for restoring traditional pigments. Therefore, this study analyzed the characteristics of NSS- and GJS-Neorok-based pigments to evaluate the feasibility of substituting GJS Neorok for NSS Neorok in pigments. The NSS Neorok was mostly comprised of celadonite, whereas the GJS Neorok included minerals containing glassy phases such as celadonite, cristobalite, tridymite, etc. Because both Neorok samples were vitrified under identical conditions, the GJS Neorok grains were larger than the NSS Neorok ones. The GJS Neorok pigment showed that the chromaticity, grain size, oil absorption, and stability varied depending on the mineral types and contents. In particular, GJS-2 and NSS Neorok showed similar mineral compositions, physical properties, and stabilities, suggesting that GJS-2 can be substituted for NSS Neorok, which has been difficult to source and utilize ever since NSS was designated as a natural monument.

Photocurrent study on the splitting of the valence band and growth of $ZnIn_{2}Se_{4}$ single crystal thin film by hot wall epitaxy (Hot wall epitaxy(HWE)법에 의한 $ZnIn_{2}Se_{4}$ 단결정 박막 성장과 가전자대 갈라짐에 대한 광전류 연구)

  • Hong, Kwang-Joon
    • Journal of the Korean Crystal Growth and Crystal Technology
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    • v.18 no.5
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    • pp.217-224
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    • 2008
  • A stoichiometric mixture of evaporating materials for $ZnIn_2Se_4$ single crystal thin films was prepared from horizontal electric furnace. To obtain the single crystal thin films, $ZnIn_2Se_4$ mixed crystal was deposited on thoroughly etched semi-insulating GaAs(100) substrate by the Hot Wall Epitaxy (HWE) system. The source and substrate temperatures were $630^{\circ}C$ and $400^{\circ}C$, respectively. The crystalline structure of the single crystal thin films was investigated by the photoluminescence and double crystal X-ray diffraction (DCXD). The carrier density and mobility of $ZnIn_2Se_4$ single crystal thin films measured from Hall effect by van der Pauw method are $9.41\times10^{16}cm^{-3}$ and $292cm^2/v{\cdot}s$ at 293 K, respectively. The temperature dependence of the energy band gap of the $ZnIn_2Se_4$ obtained from the absorption spectra was well described by the Varshni's relation, $E_g(T)=1.8622eV-(5.23\times10^{-4}eV/K)T^2/(T+775.5K)$. The crystal field and the spin-orbit splitting energies for the valence band of the $ZnIn_2Se_4$ have been estimated to be 182.7 meV and 42.6 meV, respectively, by means of the photocurrent spectra and the Hopfield quasicubic model. These results indicate that the splitting of the ${\Delta}so$ definitely exists in the ${\Gamma}_5$ states of the valence band of the $ZnIn_2Se_4/GaAs$ epilayer. The three photo current peaks observed at 10 K are ascribed to the $A_{1}-$, $B_{1}-exciton$ for n = 1 and $C_{27}-exciton$ peaks for n = 27.

Optical Properties of InAs Quantum Dots Grown by Changing Arsenic Interruption Time (As 차단 시간 변화에 의한 InAs 양자점의 광학적 특성)

  • Choi, Yoon Ho;Ryu, Mee-Yi;Jo, Byounggu;Kim, Jin Soo
    • Journal of the Korean Vacuum Society
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    • v.22 no.2
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    • pp.86-91
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    • 2013
  • The optical properties of InAs quantum dots (QDs) grown on GaAs substrates grown by molecular beam epitaxy have been studied using photoluminescence (PL) and time-resolved PL measurements. InAs QDs were grown using an arsenic interruption growth (AIG) technique, in which the As flux was periodically interrupted by a closed As shutter during InAs QDs growth. In this study, the shutter of As source was periodically opened and closed for 1 (S1), 2 (S2), or 3 s (S3). For comparison, an InAs QD sample (S0) without As interruption was grown in a pure GaAs matrix for 20 s. The PL intensity of InAs QD samples grown by AIG technique is stronger than that of the reference sample (S0). While the PL peaks of S1 and S2 are redshifted compared to that of S0, the PL peak of S3 is blueshifted from that of S0. The increase of the PL intensity for the InAs QDs grown by AIG technique can be explained by the reduced InAs clusters, the increased QD density, the improved QD uniformity, and the improved aspect ratio (height/length). The redshift (blueshift) of the PL peak for S1 (S3) compared with that for S0 is attributed to the increase (decrease) in the QD average length compared to the average length of S0. The PL intensity, PL peak position, and PL decay time have been investigated as functions of temperature and emission wavelength. S2 shows no InAs clusters, the increased InAs QD density, the improved QD uniformity, and the improved QD aspect ratio. S2 also shows the strongest PL intensity and the longest PL decay time. These results indicate that the size (shape), density, and uniformity of InAs QDs can be controlled by using AIG technique. Therefore the emission wavelength and luminescence properties of InAs/GaAs QDs can also be controlled.

Inhibitory Effects of Ethanol Extracts from Polygoni multiflori radix and Cynanchi wilfordii radix on Melanogenesis in Melanoma Cells (하수오와 백하수오의 에탄올 추출물에 의한 B16/F10 Melanoma 세포주의 멜라닌 생성 억제효과)

  • Seo, Hee;Seo, Geun-Young;Ko, Su-Zie;Park, Young-Hyun
    • Journal of the Korean Society of Food Science and Nutrition
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    • v.40 no.8
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    • pp.1086-1091
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    • 2011
  • Anti-oxidative activity and tyrosinase inhibitory activity of various ethanol extracts of Polygoni multiflori radix (PMR) and Cynanchi wilfordii radix (CWR) were compared to identify an anti-oxidant and whitening agent source from nature. We conducted an investigation into the anti-oxidant activities of PMR and CWR ethanol extracts by measuring total polyphenol content, total flavonoid content, and ABTS radical capacity. The total polyphenol contents of PMR and CWR were 17.31${\pm}$0.54 mg GA/eq g, and 2.75${\pm}$0.22 mg GA/eq g, respectively. The total flavonoid contents of PMR and CWR were 6.38${\pm}$0.39 mg naringine/eq g, and 1.34${\pm}$0.09 mg naringine/eq g, respectively. The 2,2'-azino-bis(3-ethylbenzthiazoline-6-sulphonic acid) radical decolorization of PMR and CWR were 96.89${\pm}$0.21% at 1 mg/mL and 93.49${\pm}$0.76% at 50 mg/mL. Melanoma cells were cultured with the PMR and CWR ethanol extracts for 48 hr, and total melanin content as a final product and the activity of tyrosinase, a key enzyme, in melanogenesis, were estimated. The PMR and CWR ethanol extracts increased melanin content and tyrosinase activity in a dose-dependent manner. These results suggest that PMR and CWR ethanol extracts could be useful as a skin whitening agent.

Anti-inflammatory and Anti-bacterial Activities of Artemisia iwayomogi Kitamura Extract Fractions (한인진 분획물의 항염증, 항균 효과)

  • Sin, Seung Mi;Jeong, Won Min;Kil, Young Sook;Lee, Dong Yeol;Kim, Sang Gon;Goo, Young-Min
    • Journal of Life Science
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    • v.30 no.1
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    • pp.40-44
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    • 2020
  • This study investigated the anti-bacterial and anti-inflammatory activities of Artemisia iwayomogi Kitamura for medical and food additive applications. A 70% methanol extract of A. iwayomogi Kitam. was fractionated with a series of solvents in order of increasing polarity; these fractionated extracts showed high 2,2-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt (ABTS) scavenging activity in the ethyl acetate fractions and high 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activity in both the ethyl acetate and chloroform fractions. Levels of total phenolics and flavonoids were highest in the ethyl acetate fraction extracts. Eight bacteria were then treated with the A. iwayomogi Kitam. extract fractions and most showed similar or lower levels of anti-bacterial activity when compared to the control group, except for Staphylococcus aureus. In addition, the anti-oxidant activities of the ethyl acetate fractions of the A. iwayomogi Kitam. extract were higher than those of the other fractions. To confirm the anti-inflammatory activity of the extract fractions, we applied them to RAW 264.7 cells using LPS, and the results indicate that an ethyl acetate fraction at 250 ㎍/ml concentration inhibits nitric oxide production. This study demonstrates that an ethyl acetate fraction of A. iwayomogi Kitam. extract inhibits bacterial and inflammatory activities and could be useful as a potential source of bioactive compounds.

Distributed Amplifier with Control of Stability Using Varactors (가변 커패시터를 이용하여 안정도를 조절할 수 있는 Distributed Amplifier)

  • Chu Kyong-Tae;Jeong Jin-Ho;Kwon Young-Woo
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
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    • v.16 no.5 s.96
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    • pp.482-487
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    • 2005
  • In this paper, we propose the control method of output impedance of each cascode unit cell of distributed amplifier by connecting varactors in the gate-terminal of common gate. Compared to common source unit cell, cascode unit cell has many advantages such as high gain and high output impedance as well as negative resistance loading. But if the transistor model which is used in design is inaccurate and process parameter is changed, oscillation sometimes can occur at band edge in which the gain start to drop. Therefore, we need control circuit which can prevent oscillation, although the circuit has already fabricated, and varactor connected to gate-terminal of common gate of cascode gain cell can play that part. Measured result of fabricated distributed amplifier shows the capability of contol of gain characteristic by adjusting of value of varactors, this can guarantee the stability of the circuit. The gain is $8.92\pm0.82dB$ over 49 GHz, the group delay is $\pm9.3 psec$ over 41 GHz. All transistor which has $0.15{\mu}m$ gate length is GaAs based p-HEMT, and distributed amplifier is put together with 4 stages.

Growth and optical characterization of $CuInSe_2$ single crystal thin film for solar cell application (태양전지용 $CuInSe_2$단결정 박막 성장과 광학적 특성)

  • 백승남;홍광준
    • Journal of the Korean Crystal Growth and Crystal Technology
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    • v.12 no.4
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    • pp.202-209
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    • 2002
  • The stochiometric mix of evaporating materials for the $CuInSe_2$single crystal thin films was prepared from horizontal furnace. To obtain the single crystal thin films, $CuInSe_2$compound crystal was deposited on thoroughly etched semi-insulating GaAs(100) substrate by the Hot Wall Epitaxy (HWE) system. The source and substrate temperature were $620^{\circ}C$ and $410^{\circ}C$, respectively. The crystalline structure of single crystal thin films was investigated by the photoluminescence and double crystal X-ray diffraction (DCXD). The carrier density and mobility of $CuInSe_2$single crystal thin films measured from Hall effect by van der Pauw method. From the photocurrent spectrum by illumination of perpendicular light on the c-axis of the $CuInSe_2$single crystal thin film, we have found that the values of spin orbit splitting $\Delta$So and the crystal field splitting $\Delta$Cr. From the photoluminescence measurement on $CuInSe_2$single crystal thin film, we observed free exciton ($E_x$) existing only high quality crystal and neutral bound exciton ($A^{\circ}$, X) having very strong peak intensity. Then, the full-width-at-half-maximum (FWHM) and binding energy of neutral donor bound exciton were 7 meV and 5.9 meV, respectivity. By haynes rule, an activation energy of impurity was 59 meV.