• Title/Summary/Keyword: electron temperature measurement

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A study on radiation degradation of LDPE by using ESR (ESR을 이용한 저밀도 폴리에틸렌의 방사선 열화에 관한 연구)

  • Kim, Ki-Yup;Kim, Jin-Ah;Lee, Chung;Kim, Pyeong-Jong;Ryu, Boo-Hyung
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2004.07a
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    • pp.473-476
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    • 2004
  • This study has investigated radiation degradation of low density polyethylene(LDPE). Samples were irradiated using a $Co^{60}\;\gamma-ray$ and ray up to 800 kGy at a dose rate of 5 kGy/hr in the presence of air atmosphere at room temperature. After irradiation, free radical measurement of LDPE has established by electron spin resonance(ESR). Then, each sample was stored for 2 weeks. ESR measurement showed that free radical concentration(FRC) was increased with radiation dose and changed from alkyl, allyl radical to peroxy radical with time.

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Detection and Manipulation of Spin state of Single Molecule Magnet: Kondo resonance and ESR-STM

  • Komeda, T.;Isshiki, H.;Zhang, Y.F.;Katoh, K.;Yoshida, Y.;Yamashita, M.;Miyasaka, H.;Breedlove, B.K.
    • Proceedings of the Korean Vacuum Society Conference
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    • 2010.02a
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    • pp.16-17
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    • 2010
  • Molecular spintronics has attracted attentions, which combines molecular electronics with the spin degree of freedom in electron transport. Among various molecules as candidates of the molecular spintronics, single molecule magnet (SMM) is one of the most promising material. SMM molecules show a ferromagnetic behavior even as a single molecule and hold the spin information even after the magnetic field is turned off. Here in this report, we show the spin behavior of SMM molecules adsorbed on the Au surface by combining the observation of Kondo peak in the STS and ESR-STM measurement. Kondo resonance state is formed near the Fermi level when degenerated spin state interacts with conduction electrons. ESR-STM detects the Larmor frequency of the spin in the presence of a magnet field. The sample include $MPc_2$ and $M_2Pc_3$ molecules ($M\;=\;Tb^{3+}$, $Dy^{3+}$, and $Y^{3+}$ Pc=phthalocyanine) whose critical temperature as a ferromagnet reaches 40 K. A clear Kondo peak was observed which is originated from an unpaired electron in the ligand of the molecule, which is the first demonstration of the Kondo peak originated from electron observed in the STS measurement. We also observed corresponding peaks in ESR-STM spectra. [1] In addition we found that the Kondo peak intensity shows a clear variation with the conformational change of the molecule; namely the azimuthal rotational angle of the Pc planes. This indicates that the Kondo resonance is correlated with the molecule electronic state. We examined this phenomena by using STM manipulation technique, where pulse bias application can rotate the relative azimuthal angle of the Pc planes. The result indicates that an application of ~1V pulse to the bias voltage can rotate the Pc plane and the Kondo peaks shows a clear variation in intensity by the molecule's conformational change.

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Oxygen Plasma Effect on AlGaN/GaN HEMTs Structure Grown on Si Substrate

  • Seo, Dong Hyeok;Kang, Sung Min;Lee, Dong Wha;Ahn, Du Jin;Park, Hee Bin;Ahn, Youn Jun;Kim, Min Soo;Kim, Yu Kyeong;Lee, Ho Jae;Song, Dong Hun;Kim, Jae Hee;Bae, Jin Su;Cho, Hoon Young
    • Proceedings of the Korean Vacuum Society Conference
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    • 2013.02a
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    • pp.420-420
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    • 2013
  • We investigated oxygen plasma effect on defect states near the interface of AlGaN/GaN High Electron Mobility Transistor (HEMT) structure grown on a silicon substrate. After the plasma treatment, electrical properties were evaluated using a frequency dependant Capacitance-Voltage (C-V) and a temperature dependant C-V measurements, and a deep level transient spectroscopy (DLTS) method to study the change of defect densities. In the depth profile resulted from the temperature dependant C-V, a sudden decrease in the carrier concentration for two-dimensional electron gas (2DEG) nearby 250 K was observed. In C-V measurement, the interface states were improved in case of the oxygen-plasma treated samples, whereas the interface was degraded in case of the nitrogen-plasma treated sample. In the DLTS measurement, it was observed the two kinds of defects well known in AlGaN/GaN structure grown on sapphire substrate, which have the activation energies of 0.15 eV, 0.25 eV below the conduction band. We speculate that this defect state in AlGaN/GaN on the silicon substrate is caused from the decrease in 2DEG's carrier concentrations. We compared the various DLTS signals with filling pulse times to identify the characteristics of the newly found defect. In the filling pulse time range under the 80 us, the activation energies changed as the potential barrier model. On the other hand, in the filling pulse time range above the 80 us, the activation energies changed as the extended potential model. Therefore, we suggest that the found defect in the AlGaN/GaN/Si structure could be the extended defect related with AlGa/N/GaN interface states.

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Nonstoichiometric Addition of ZrO2 and NiO to the Ba(Zn1/3Ta2/3)O3 Microwave Dielectrics (Ba(Zn1/3Ta2/3)O3 마이크로파 유전체에서 ZrO2와 NiO의 비화학양론적 첨가)

  • Nam, Kyung-Deog;Kang, Sung-Woo;Kim, Tae-Heui;Sim, Soo-Man;Choi, Sun-Hee;Kim, Joo-Sun
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.24 no.12
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    • pp.955-961
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    • 2011
  • We investigated the physical properties of stoichiometric and non-stoichiometric oxide doped complex perovskite, $Ba(Zn_{1/3}Ta_{2/3})O_3$ ceramics and their impacts on the microwave dielectric performances using various characterization techniques such as X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and network analyzer. According to the measurement of lattice constant changes, anomalous lattice volume contraction of $ZrO_2$ doped $Ba(Zn_{1/3}Ta_{2/3})O_3$ sample only showed the dielectric quality factor enhancements, which was due to the lattice volume contraction as well as the 1:2 B-site cation ordering. In addition, NiO doping was useful to the stabilization of temperature coefficient of resonance frequency.

Growth of $In_{0.53}Ga_{0.47}As$ Iattice matched to Inp substrate by low pressure metalorganic chemical vapor deposition (저압 유기금속 화학증착법을 이용한 InP 기판에 격자 일치된 $In_{0.53}Ga_{0.47}As$ 에피층의 성장)

  • 박형수;문영부;윤의준;조학동;강태원
    • Journal of the Korean Vacuum Society
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    • v.5 no.3
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    • pp.206-212
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    • 1996
  • $In_{1-x}Ga_xAs$ epitaxial layers were grown at 76 Torr by low pressure metalorganic chemical vapor deposition (LP-MOCVD). Growth rate did not change much with growth temperature. Surface morphology of $In_{1-x}Ga_xAs$ epitaxial layer was affected by lattice mismatch, growth temperature and $AsH_3/(TMIn+TMGa)$ ratio. A high quality epilayer showed a full width at half maximum of 2.8 meV by photoluminescence measurement at 5K. The composition of the $In_{1-x}Ga_xAs$ was determined by the relative gas phase diffusion of TMIn and TMGa. Lattice mismatch and growth temperature were the most important variables that determine the electrical properties of $In_{1-x}Ga_xAs$ epitaxial layers. At optimized growth condition, it was possible to obtain a high quality $In_{1-x}Ga_xAs$ epilayers with a electron concentration as low as $8{\times}10^{14}/cm^3$ and an electron mobility as high as 11,000$\textrm{cm}^2$/Vsec at room temperature.

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Temperature dependence of Heteroeptaxial $Y_2O_3$ films grown on Si by ionized cluster beam deposition

  • Cho, M.-H.;Ko, D.-H.;Whangbo, S.W.;Kim, H.B.;Jeong, K.H.;Whang, C.N.;Choi, S.C.;Cho, S.J.
    • Journal of the Korean Vacuum Society
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    • v.7 no.s1
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    • pp.57-77
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    • 1998
  • Heteroepitaxial $Y_2O_3$ films were grown on a Si(111) substrate by ionized cluster beam deposition(ICBD) in ultra high vacuum, and its qualities such as crystllitnity, film stress, and morphological characteristics were investigated using the various measurement methods. The crystallinity was investigated by x-ray diffraction (XRD) and reflection high energy electron diffraction (RHEED). Interface crystallinity was also examined by Rutherford backscattering spectroscopy(RBS) channeling, transmission electron microscopy(TEM). The stress of the films was measured by RBS channeling and XRD. Surface and interface morphological characteristics were investigated by atomic force microscopy (AFM) and x-ray scattering method. Comparing the interface with the surface characteristics, we can conclude that many defects at the interface region were generated by interface reaction between the yttrium metal and SiO2 layer and by ion beam characteristic such as shallow implantation, so that they influenced the film qualities. The film quality was dominantly depended on the characteristic temperature range. In the temperature range from $500^{\circ}C$ to $600^{\circ}C$, the crystallinity was mainly improved and the surface roughness was drastically decreased. On the other hand, in the temperature range from $600^{\circ}C$ to $700^{\circ}C$, the compressive stress and film density were dominantly increased, and the island size was more decreased. Also the surface morphological shape was transformed from elliptical shape to triangular. The film stress existed dominantly at the interface region due to the defects generation.

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A Study on the Effect of Plasma Deuterium Treatment on Reliability of Poly-Silicon Thin Film Transistors (중수소 프라즈마 처리가 다결정 실리콘 TFT의 안정성에 미치는 영향에 관한 연구)

  • Sohn Song Ho;Bae S. C.;Kim Donghwan
    • Korean Journal of Materials Research
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    • v.14 no.7
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    • pp.516-521
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    • 2004
  • We applied a deuterium plasma treatment to the surface of polycrystalline silicon films using PECVD and observed the change with AFM, XRD, ET-IR, and SIMS measurement. A bias temperature stressing (BTS) test was carried out to evaluate the reliability of the thin-film transistors (TFT). TFTs with channel lengths as small as 2 ${\mu}m$ were electrically stressed fer up to 1000 sec at room temperature. From the parameter variation such as s-factor, leakage current and on/off ratio, we suggest that the deuterium plasma treatment suppress the hot carrier effect and improve the stability of TFTs.

Crystallization of Passivation Glass for Electronic Devices (전자장치용 Passivation 유리의 결정화에 관한 연구)

  • 손명모;박희찬;이헌수
    • Journal of the Korean Ceramic Society
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    • v.30 no.2
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    • pp.107-114
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    • 1993
  • Zinc-Borosilicate(ZnO 65.0wt%, B2O3 21.5wt%, SiO2 9.0wt%, PbO or tiO2 4wt%) passivation glasses were studied using differential thermal analysis(DTA), scanning electron microscopy(SEM) observations, X-ray diffraction (XRD) patterns and measurement of thermal expansion coefficients. Passivation glasses containing 4wt% TiO2 and 4wt% PbO had crystallization temperature of 680~73$0^{\circ}C$ and major crystalline phases were identified by X-ray diffraction as $\alpha$-ZnO.B2O3 and $\alpha$-5ZnO.2B2O3. As increasing firing temperature, the size of crystalline phases increased by observation of SEM. The thermal expansion coefficient of crystallized glass frits was smaller than that of unfired glass.

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Surface Potential Properties of CuPc/Au Interface with Varying Temperature (CuPc/Au 계면에서의 온도 변화에 따른 표면전위 특성)

  • Lee, Ho-Shik;Park, Yong-Pil
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.21 no.10
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    • pp.934-937
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    • 2008
  • Organic field-effect transistors (OFETs) are of interest for use in widely area electronic applications. We fabricated a copper phthalocyanine (CuPc) based field-effect transistor with different metal electrode. So we need the effect of the substituent group attached to the phthalocyanine on the surface potential was investigated by Kelvin probe method with varying temperature of the substrate. We were obtained the positive shift of the surface potential for CuPc thin film. We observed the electron displacement at the interface between Au electrode and CuPc layer and we were confirmed by the surface potential measurement.

Metal-Mold Reaction and Surface Roughness Measurement of Pure Titanium Casting Specimens with Mold Temperatures (순수 티타늄 주조체의 주형온도에 따른 용탕반응성 및 표면거칠기)

  • Cha, Sung-Soo;Song, Young-Ju;Park, Soo-Chul
    • Journal of Technologic Dentistry
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    • v.32 no.4
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    • pp.297-305
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    • 2010
  • Purpose: The purpose of this study was to observe the change of metal-mold reaction and surface roughness in titanium casting specimens for phosphate-silica alumina bonded investment with mold temperatures. Methods: The metal-phosphate silica alumina bonded mold interface reaction and surface roughness of titanium casting specimens according to mold temperatures were investigated. The Specimens were analysed by scanning electron microscopy and surface roughness tester. Results: The oxidation behavior indicated by the growth of oxide thickness. The titanium-oxide layer were consisted two layer of a porous external and a dense internal one. The reaction layer and surface roughness increased with increasing investment material temperature. Conclusion: In this work, The most suitable mold temperature in casting of pure titanium was $200^{\circ}C$.