• 대한전기학회:학술대회논문집
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• 대한전기학회 1990년도 추계학술대회 논문집 학회본부
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• pp.85-87
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• 1990

Silicon nitride film was deposited on a silicon wafer using a laser CVD(LCVD) technique, which is based on direct photolysis of $SiH_4/NH_3$ gas mixture by ArF laser beam(${\lambda}=193\;nm$). The refractive index of deposited SiN film is 1.9 at the temperature of $300^{\circ}C$, pressure of 5 torr. The breakdown field strength of LCVD SiN film was 10MV/cm. In IR spectrum, the absorption peak of Si-H, N-H, and Si-N is detected and it is shown that hydrogen is included in SiN film. From analysis of absorption band. it is calculated that density of Si-H, N-H bond is higher than $5{\times}10^{22}cm^{-3}$. LCVD MIS capacitor and PECVD MIS capacitor have injection-type hysteresis but it is known that hysteresis loss of LCVD MIS capacitor is smaller than that of PECVD MIS capacitor. It means that Interface state density of LCVD capacitor is smaller than that of PECVD capacitor. In addition, the flatband voltage($V_{FB}$) of LCVD is smaller than that of PECVD capacitor. And it means that fixed charged density($Q_{FIX}$) of LCVD capacitor is smaller than that of PECVD MIS capacitor.

• 한국진공학회지
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• 제10권3호
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• pp.321-327
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• 2001

Radio frequency magnetron sputtering방법으로 타켈의 Ti/si 조성과 $N_2$ 유량을 변화시켜 증착한 다양한 조성비의 Ti-Si-N 박막의 비저항 변화와 확산방지능력을 조사하였다. 높은 Si 함량을 포함한 Ti-Si-N박막내의 Si은 주로 비정질의 $Si_3N_4$ 형태로 존재하였으며 $N_2$의 양이 증가함에 따라 비저항도 증가하였다. 반면, 낮은 Si 함량을 포함한 Ti-Si-N박막은 낮은 $N_2$ 유량에서도 결정질의 TiN이 형성되었고 낮은 비저항을 나타내었다. 또한, 박막내의 N의 양이 증가함에 따라, 높은 박막의 밀도와 압축응력을 갖는 Ti-Si-N이 형성되었으며, 이는 박막 내의 N의 함량이 확산방지능력에 영향을 미치는 가장 중요한 요소 중 하나로 판단된다. 결과적으로, 29~49 at.%, Ti, 6~20 at.% Si, 45~55 at.% N 범위의 조성을 갖는 Ti-Si-N박막이 우수한 확산 억제 능력을 보유하면서 또한 낮은 비저항 특성을 나타내는데 적합한 조성 범위로 나타났다.

• 한국전자통신학회논문지
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• 제8권4호
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• pp.549-554
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• 2013

CVD를 이용하여 Cu 시편에 그래핀의 합성을 보이고, Cu 시편의 grain 크기와 방향성에 따른 그래핀의 성장거동을 보이고자 한다. 동일한 온도 및 압력 하에서도 사용하는 분위기 가스의 종류에 따라서 Cu의 확산에 영향을 주게 되고, 그래핀 합성 시 사용되는 $H_2$와 $CH_4$ 가스 분위기 하에서 Cu grain의 성장에도 영향을 미치는 것을 알 수 있었으며, 결과적으로 Cu grain의 성장이 그래핀의 합성과 성장에 직접적인 관련이 있음을 보이고자 하였다. 부식 저항성은 상온에서 동전위 분극실험를 통하여 분석하였으며, 부식속도 비교에서 그래핀 코팅된 Cu 시편의 경우가 그래핀의 화학적 안정성에 기인하여 순수 Cu 시편의 경우보다 동일한 부식 환경에서 약 10배 정도 안정적인 것으로 관찰이 되었다. 또한, grain boundary를 포함, 결함이 없는 그래핀의 균일한 성장의 가능성을 보이고, 이의 합성을 통한 공학적인 활용이 그 최종적인 목적이 될 것이다.

• Bulletin of the Korean Chemical Society
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• 제23권2호
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• pp.225-228
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• 2002

Amorphous $Ga_2O_3$ films have been grown on Si(100) substrates by metal organic chemical vapor deposition (MOCVD) using gallium isopropoxide, $Ga(O^iPr)_3$, as single precursor. Deposition was carried out in the substrate temperature range 400-800 $^{\circ}C$. X-ray photoelectron spectroscopy (XPS) analysis revealed deposition of stoichiometric $Ga_2O_3$ thin films at 500-600 $^{\circ}C$. XPS depth profiling by $Ar^+$ ion sputtering indicated that carbon contamination exists mostly in the surface region with less than 3.5% content in the film. Microscopic images of the films by scanning electron microscopy (SEM) and atomic force microscopy (AFM) showed formation of grains of approximately 20-40 nm in size on the film surfaces. The root-mean-square surface roughness from an AFM image was ${\sim}10{\AA}$. The interfacial layer of the $Ga_2O_3$/Si was measured to be ${\sim}35{\AA}$ thick by cross-sectional transmission electron microscopy (TEM). From the analysis of gaseous products of the CVD reaction by gas chromatography-mass spectrometry (GC-MS), an effort was made to explain the CVD mechanism.

• 대한기계학회논문집B
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• 제24권11호
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• pp.1535-1539
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• 2000

A sonic nozzle is used as a reference flow meter in the area of gas flow rate measurement. The critical pressure ratio of sonic nozzle is an important factor in maintaining its operating condition. ISO9300 suggested the critical pressure ratio of sonic nozzle as a function of area ratio. In this study, 13 sonic nozzles were made by the design of ISC9300 with different half diffuser angles of 2。 to 8。 and throat diameters of 0.28 to 4.48 mm. The test results of half diffuser angles below 8。 ar quite similar to those of ISO9300. On the other hand, the critical pressure ratio for the nozzle of 8。 decreases by 5.5% in comparison with ISO9300. However, ISO9300 does not predict the critical pressure ratio at lower Reynolds numbers than 10(sup)5. Therefore, it is found that it is a better way for the flow of low Reynolds number to express the critical pressure ratio of sonic nozzle as a function of Reynolds number than area ratios. A correlation equation of critical pressure is introduced with uncertainty $\pm$3.2 % at 95% confidence level.

• Journal of Welding and Joining
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• 제33권2호
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• pp.8-13
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• 2015

This study was carried out to evaluate mechanical properties of the jointed Al6061/HT590 alloys by friction stir welding (FSW). FSW was conducted under the conditions with tool rotating speed of 500 RPM and traveling speed of 300 mm/min., where Ar gas was introduced to prevent the materials from corrosion during the welding process. Electron back-scattering diffraction (EBSD) was used to characterize microstructures such as grain size, misorientation angle and crystal orientation. Evolution of intermetallic compounds in Al6061 during the process were examined in terms of morphology, size and aspect ratio at three distinct zones Al base material, heat affected zone and stir zone, where transmission electron microscope (TEM) was used. It was revealed that FSW gave rise to refinement of grains as well as growth of intermetallic compounds in Al6061. The morphological changes of intermetallic compounds exerted an influence on mechanical properties, resulting in occurrence of fracture in the part of the base material instead of the jointed parts (heat affected zone and stir zone). This study systematically evaluated the microstructural evolutions during the FSW for joining Al6061 with HT590 and their effect on mechanical properties.

• 한국재료학회:학술대회논문집
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• 한국재료학회 2011년도 추계학술발표대회
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• pp.17.2-17.2
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• 2011

Double-walled carbon nanotubes (DWCNTs) were grown with vertical alignment on a Si wafer by using catalytic thermal chemical vapor deposition. This study investigated the effect of pre-annealing time of catalyst on the types of CNTs grown on the substrate. The catalyst layer is usually evolved into discretely distributed nanoparticles during the annealing and initial growth of CNTs. The 0.5-nm-thick Fe served as a catalyst, underneath which Al was coated as a catalyst support as well as a diffusion barrier on the Si substrate. Both the catalyst and support layers were coated by using thermal evaporation. CNTs were synthesized for 10 min by flowing 60 sccm of Ar and 60 sccm of H2 as a carrier gas and 20 sccm of C2H2 as a feedstock at 95 torr and $750^{\circ}C$. In this study, the catalyst and support layers were subject to annealing for 0~420 sec. As-grown CNTs were characterized by using field emission scanning electron microscopy, high resolution transmission electron microscopy, Raman spectroscopy, and atomic force microscopy. The annealing for 90~300 sec caused the growth of DWCNTs as high as ~670 ${\mu}m$ for 10 min while below 90 sec and over 420 sec 300~830 ${\mu}m$-thick triple and multiwalled CNTs occurred, respectively. Several radial breathing mode (RBM) peaks in the Raman spectra were observed at the Raman shifts of 112~191 cm-1, implying the presence of DWCNTs, TWCNTs, MWCNTs with the tube diameters 3.4, 4.0, 6.5 nm, respectively. The maximum ratio of DWCNTs was observed to be ~85% at the annealing time of 180 sec. The Raman spectra of the as-grown DWCNTs showed low G/D peak intensity ratios, indicating their low defect concentrations. As increasing the annealing time, the catalyst layer seemed to be granulated, and then grown to particles with larger sizes but fewer numbers by Ostwald ripening.

• 한국재료학회:학술대회논문집
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• 한국재료학회 2011년도 추계학술발표대회
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• pp.16.2-16.2
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• 2011

Graphene has attracted significant attention due to its unique characteristics and promising nanoelectronic device applications. For practical device applications, it is essential to synthesize high-quality and large-area graphene films. Graphene has been synthesized by eloborated mechanical exfoliation of highly oriented pyrolytic graphite, chemical reduction of exfoliated grahene oxide, thermal decomposition of silicon carbide, and chemical vapor deposition (CVD) on metal substrates such as Ni, Cu, Ru etc. The CVD has advantages over some of other methods in terms of mass production on large-areas substrates and it can be easily separated from the metal substrate and transferred to other desired substrates. Especially, plasma-enhanced CVD (PECVD) can be very efficient to synthesize high-quality graphene. Little information is available on the synthesis of graphene by PECVD even though PECVD has been demonstrated to be successful in synthesizing various carbon nanostructures such as carbon nanotubes and nanosheets. In this study, we synthesized graphene on $Ni/SiO_2/Si$ and Cu plate substrates with CH4 diluted in $Ar/H_2$ (10%) by using an inductively-coupled PECVD (ICPCVD). High-quality graphene was synthesized at as low as $700^{\circ}C$ with 600 W of plasma power while graphene layer was not formed without plasma. The growth rate of graphene was so fast that graphene films fully covered on substrate surface just for few seconds $CH_4$ gas supply. The transferred graphene films on glass substrates has a transmittance at 550 nm is higher 94%, indicating 1~3 monolayers of graphene were formed. FETs based on the grapheme films transferred to $Si/SiO_2$ substrates revealed a p-type. We will further discuss the synthesis of graphene and doped graphene by ICPVCD and their characteristics.

• 한국재료학회지
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• 제24권12호
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• pp.694-699
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• 2014

We report the chemical vapor deposition growth characteristics of graphene on various catalytic metal substrates such as Ni, Fe, Ag, Au, and Pt. 50-nm-thick metal films were deposited on $SiO_2/Si$ substrates using dc magnetron sputtering. Graphene was synthesized on the metal/$SiO_2$/Si substrates with $CH_4$ gas (1 SCCM) diluted in mixed gases of 10% $H_2$ and 90 % Ar (99 SCCM) using inductively-coupled plasma chemical vapor deposition (ICP-CVD). The highest quality of graphene film was achieved on Ni and Fe substrates at $900^{\circ}C$ and 500 W of ICP power. Ni substrate seemed to be the best catalytic material among the tested materials for graphene growth because it required the lowest growth temperature ($600^{\circ}C$) as well as showing a low ICP power of 200W. Graphene films were successfully grown on Ag, Au, and Pt substrates as well. Graphene was formed on Pt substrate within 2 sec, while graphene film was achieved on Ni substrate over a period of 5 min of growth. These results can be understood as showing the direct CVD growth of graphene with a highly efficient catalytic reaction on the Pt surface.

• 한국재료학회지
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• 제28권4호
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• pp.208-213
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• 2018

Epitaxial ($11{\bar{2}}0$) a-plane GaN films were grown on a ($1{\bar{1}}02$) R-plane sapphire substrate with photoresist (PR) masks using metal organic chemical vapor deposition (MOCVD). The PR mask with striped patterns was prepared using an ex-situ lithography process, whereas carbonization and heat treatment of the PR mask were carried out using an in-situ MOCVD. The heat treatment of the PR mask was continuously conducted in ambient $H_2/NH_3$ mixture gas at $1140^{\circ}C$ after carbonization by the pyrolysis in ambient $H_2$ at $1100^{\circ}C$. As the time of the heat treatment progressed, the striped patterns of the carbonized PR mask shrank. The heat treatment of the carbonized PR mask facilitated epitaxial lateral overgrowth (ELO) of a-plane GaN films without carbon contamination on the R-plane sapphire substrate. Thhe surface morphology of a-plane GaN films was investigated by scanning electron microscopy and atomic force microscopy. The structural characteristics of a-plane GaN films on an R-plane sapphire substrate were evaluated by ${\omega}-2{\theta}$ high-resolution X-ray diffraction. The a-plane GaN films were characterized by X-ray photoelectron spectroscopy (XPS) to determine carbon contamination from carbonized PR masks in the GaN film bulk. After $Ar^+$ ion etching, XPS spectra indicated that carbon contamination exists only in the surface region. Finally, the heat treatment of carbonized PR masks was used to grow high-quality a-plane GaN films without carbon contamination. This approach showed the promising potential of the ELO process by using a PR mask.