• Transactions on Electrical and Electronic Materials
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• 제12권5호
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• pp.200-203
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• 2011

In this research, nitrogen (N)-doped zinc oxide (ZnO) thin films have been grown on a sapphire substrate by dielectric barrier discharge (DBD) in pulsed laser deposition (PLD). DBD has been used as an effective way for massive in-situ generation of N-plasma under conventional PLD process conditions. Low-temperature photoluminescence spectra of N-doped ZnO thin films provided near-band-edge emission after a thermal annealing process. The emission peak was resolved by Gaussian fitting and showed a dominant acceptor-bound excitation peak ($A^{\circ}X$) that indicated acceptor doping of ZnO with N. The acceptor binding energy of the N acceptor was estimated to be approximately 145 MeV based on the results of temperature-dependent photoluminescence (PL) measurements.

• JSTS:Journal of Semiconductor Technology and Science
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• 제3권2호
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• pp.96-101
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• 2003

Direct evidence on the incorporation of high concentration of oxygen into undoped AlGaN layers for the AlGaN/GaN heterostuctures is provided by scanning photoemission microscopy using synchrotron radiation. In-situ annealing at $1000^{\circ}C$ resulted in a significant increase in the oxygen concentration at the AlGaN surface due to the predominant formation of Al-O bonds. The oxygen incorporation into the AlGaN layers resulting from the high reactivity of Al to oxygen can enhance the tunneling-assisted transport of electrons at the metal/AlGaN interface, leading to the reduction of the Schottky barrier height and the increase of the sheet carrier concentration near the AlGaN/GaN interface.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2010년도 제39회 하계학술대회 초록집
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• pp.84-84
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• 2010

We present an in-situ study of the interaction of a bimetallic Rh50Pd50 bulk crystal with O2, CO, and NO using ambient pressure x-ray photoelectron spectroscopy and compare it to results for 10 nm nanoparticles with the same overall composition. The surface of the bulk crystal has less Rh present under both oxidizing and reducing conditions than the nanoparticles under identical conditions. Segregation and oxidation/reduction proceeds quicker and at lower temperature for nanoparticles than for the bulk crystal. The near surface of the Rh50Pd50 bulk crystal after high temperature vacuum annealing is ca. 9% Rh measured by XPS. Heating in 0.1 Torr O2 to $350^{\circ}C$ increases the Rh surface composition to ca. 40%. The surface can then be reduced by heating in H2 at $150^{\circ}C$, leading to a reduced surface of 30% Rh. Titration of CO from this Rh-rich surface proceeds at a much lower pressure than on the Rh-deficient starting surface.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2013년도 제45회 하계 정기학술대회 초록집
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• pp.131-131
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• 2013

A single-layer graphene has been uniformly grown on a Cu surface at elevated temperatures by thermally processing a poly(methyl methacrylate) (PMMA) film in a rapid thermal annealing (RTA) system under vacuum. The detailed chemistry of the transition from solid-state carbon to graphene on the catalytic Cu surface was investigated by performing in-situ residual gas analysis while PMMA/Cu-foil samples being heated, in conjunction with interrupted growth studies to reconstruct ex-situ the heating process. The data clearly show that the formation of graphene occurs with hydrocarbon molecules vaporized from PMMA, such as methane and/or methyl radicals, as precursors rather than by the direct graphitization of solid-state carbon. We also found that the temperature for vaporizing hydrocarbon molecules from PMMA and the length of time the gaseous hydrocarbon atmosphere is maintained, which are dependent on both the heating temperature profile and the amount of a solid carbon feedstock are the dominant factors to determine the crystalline quality of the resulting graphene film. Under optimal growth conditions, the PMMA-derived graphene was found to have a carrier (hole) mobility as high as ~2,700 cm2V-1s-1 at room temperature, superior to common graphene converted from solid carbon.

• E2M - 전기 전자와 첨단 소재
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• 제10권10호
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• pp.1029-1033
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• 1997

A prototype MFSFET using ferroelectric fluoride BaMgF$_4$as a gate insulator has been successfully fabricated with the help of 2 sheets of metal mask. The fluoride film was deposited in an ultrai-high vacuum system at a substrate temperature of below 30$0^{\circ}C$ and an in-situ post-deposition annealing was conducted for 20 seconds at $650^{\circ}C$ in the same chamber. The interface state density of the BaMgF$_4$/Si(100) interface calculated by a MFS capacitor fabricated on the same wafer was about 8$\times$10$^{10}$ /cm$^2$.eV. The I$_{D}$-V$_{G}$ characteristics of the MFSFET show a hysteresis loop due to the ferroelectric nature of the BaMgF$_4$film. It is also demonstrated that the I$_{D}$ can be controlled by the “write” plus which was applied before the measurements even at the same “read”gate voltage.ltage.

• The Korean Journal of Ceramics
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• 제6권2호
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• pp.91-95
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• 2000

Powder mixtures of $\beta$-SiC-TiC in a weight ratio of 2:1 containing 5-20 wt% additives ($Al_2O_3$-$Y_2O_3$) were liquid-phase sintered at $1830^{\circ}C$ for 1h by hot-pressing and subsequently annealed at $1950^{\circ}C$ for 6h to enhance grain growth. The annealed specimens revealed a microstructure of \"in situ-toughened composite\" as a result of the $\beta$longrightarrow$\alpha$ phase transformation of SiC during annealing. The increase of the content of additives accelerated the growth of elongated $\alpha$-SiC grains with higher aspect ratio and improved fracture toughness. The fracture toughness of SiC-TiC composite containing 20 wt% additive was 6.2 MPa.$m^{1/2}$.2}$.

• 한국전기전자재료학회논문지
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• 제15권7호
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• pp.576-582
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• 2002

Nonvolatile semiconductor memory devices with reoxidized nitrided oxide(RONO) gate dielectrics were fabricated, and nitrogen distribution and bonding species which contribute to memory characteristics were analyzed. Also, memory characteristics of devices depending on the anneal temperatures were investigated. The devices were fabricated by retrograde twin well CMOS processes with $0.35\mu m$ design rule. The processes could be simple by in-situ process in growing dielectric. The nitrogen distribution and bonding states of gate dielectrics were investigated by Dynamic Secondary Ion Mass Spectrometry(D-SIMS), Time-of-Flight Secondary Ion Mass Spectrometry(ToF-SIMS), and X-ray Photoelectron Spectroscopy(XPS). As the nitridation temperature increased, nitrogen concentration increased linearly, and more time was required to form the same reoxidized layer thickness. ToF-SIMS results showed that SiON species were detected at the initial oxide interface which had formed after NO annealing and $Si_2NO$ species within the reoxidized layer formed after reoxidation. As the anneal temperatures increased, the device showed worse retention and degradation properties. It could be said that nitrogen concentration near initial interface is limited to a certain quantity, so the excess nitrogen is redistributed within reoxidized layer and contribute to electron trap generation.

• 한국안광학회지
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• 제5권2호
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• pp.207-210
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• 2000

일축가압 소결 및 열처리하여 SiC-TiC 안경렌즈 절삭용 재료를 제조하였다. TiC의 함량은 0, 10, 20, 30wt%이었다. 일축가압소결 후 열처리한 안경렌즈 절삭용 복합재료의 미세구조는 TiC의 양에 크게 의존하였다. TiC의 함량이 증가할수록 파괴인성값이 증가됨을 알 수 있었다. 광학현미경과 X-ray 회질분석을 통하여 미세구조와 상분석을 하였다. 시편의 미세구조는 길게자란 SiC입자와 기지형의 TiC입자로 구성되었다. 본 연구에서 연구된 안경렌즈 절삭용 시편의 대표적인 경도와 파괴인성은 각각 14.9GPa과 $5.7MPa{\cdot}m^{1/2}$이었다.

• 한국표면공학회지
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• 제29권5호
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• pp.415-423
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• 1996

Thin film technologies for fabricating SQUIDs involve etching and deposition procedures with the proper substrate materials and $YBa_2Cu_3O_{7-d}$ (YBCO) as the high $T_c$ superconductor. YBCO were prepared on various substrates of MgO, $SrTiO_3$, and $LaAlO_3$ by using off-axis magnetron sputtering methods and annealing in-situ. The parameters of film fabrication processes had been optimized to yield good quality films in terms of the critical temperature $T_c$ and the critical current density $J_c$. The optimized processes yielded $T_C$>90K along with $J_c$>$10_6A$$extrm{cm}^2$ at 77K and>$2\times10_7A/Cm^2$ at 5K. We fabricated step-edge type dc-SQUIDs and directly coupled magnetometers, producing step edges on MgO(100) substrates by etching with Ar-ion beam, depositing YBCO material on them, then patterning them by using ion-milling technique. Circuitizing washer-shape SQUIDs to possess a pair of step-edge junctions of 2-5$\mu$ line width with a high angle>$50^{\circ}C$ , we examined their I-V characteristics thoroughly and Shapiro steps clearly as we irradiate microwaves of 8-20 GHz frequency.

• 한국자기학회지
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• 제14권3호
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• pp.89-94
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• 2004

본 연구에서는 InP(2${\times}$4) 재구성된 표면 위에 원자층 단위로 증착된 Co 박막의 특성을 표면 자기광 커 효과(surface magneto-optical Kerr effect, SMOKE) 시스템, 반사 고에너지 전자 회절(reflection high energy electron diffraction), 주사 터널링 현미경(scanning tunneling microscope)이 장착된 초고진공 챔버를 이용하여 조사하였다. 실시간(in situ) SMOKE 연구 결과, Co 박막이 InP(2${\times}$4) 재구성된 표면 위에 성장할 때, Co박막의 두께에 따라 자성 특성이 대조적으로 구분되는 세 가지 두께 영역이 존재함을 확인할 수 있었다. 즉, Co 박막 두께가 7 단층(monolayer, ML)보다 작은 두께 영역에서는 가로 방향(longitudinal)과 수직방향(polar) 측정에서 모두 SMOKE신호를 관찰할 수 없었다. 8$m\ell$에서 15$m\ell$까지의 Co두께 영역에서는 수평 자기 이방성과 수직 자기 이방성이 공존하는 준안정상(metastable phase)을 관찰할 수 있었다. 그리고 마지막 영역은 16$m\ell$이상의 두께를 갖는 영역으로 수평 자기 이방 강자성을 확인할 수 있었다.