• 한국결정성장학회지
• /
• 제9권3호
• /
• pp.303-308
• /
• 1999

As a semiconductor material for electronic devices operated under extreme environmental conditions, silicon carbides(SiCs) have been intensively studied because of their excellent electrical, thermal and other physical properties. The growth characteristics of single-crystalline 4H-SiC homoepitaxial layers grown by a thermal chemical vapor deposition (CVD) were investigated. Especially, the successful growth condition of 4H-SiC homoepitaxial layers using a SiC-uncoated atmospheric pressure chamber and carried out using off-oriented substrates prepared by a modified Lely method. In order to investigate the crystallinity of grown epilayers, Nomarski optical microscopy, Raman spectroscopy, photoluninescence(PL), scanning electron microscopy(SEM) and other techniques were utilized. The best quality of 4H-SiC homoepitaxial layers was observed in conditions of growth temperature $1500^{\circ}C$ and C/Si flow ratio 2.0 of $C_{3}H_{8}\;0.2\;sccm\;&\;SiH_{4}\;0.3\;sccm$. The growth rate of epilayers was about $1.0\mu\textrm{m}/h$ in the above growth condition.

• 한국결정성장학회지
• /
• 제17권3호
• /
• pp.91-94
• /
• 2007

Vapor liquid solid 기구에 의한 열화학기상증착법을 이용하여 Si (001) 기판 위에 $SnO_2$ 나노와이어를 성장시켰다. Au 박막 (3 nm)을 성장을 위한 촉매로 사용하여 Si(001) 기판 이에 순수 SnO powder (purity, 99.9%)를 반응 원료로 대기압 하 $950{\sim}100^{\circ}C$ 온도 범위, $750{\sim}800\;sccm$ 아르곤 분위기에서 $SnO_2$ 나노와이어를 성장시켰다. X-ray diffraction 분석을 통해 성장한 $SnO_2$ 나노와이어가 tetragonal rutile 구조임을 확인하였고, transmission electron microscopy 분석을 통해 단일 나노와이어의 결정 특성을 분석하였다. 또한, 상온 photoluminescence 분석을 통해 나노와이어 샘플로부터 600 nm 부근에서 나타나는 defect level 천이에 의한 넓은 emission band를 확인함으로써 성장한 나노와이어 $SnO_2$임을 확인하였다.

• 한국결정성장학회지
• /
• 제12권3호
• /
• pp.120-125
• /
• 2002

Si-wafers for solar cells were cast in a size of $50{\times}46{\times}0.5{\textrm}{mm}^3$ by vacuum casting method. The graphite mold coated by BN powder, which was to prevent the reaction of carbon with the molten silicon, was used. Without coating, the wetting and reaction of Si melt to graphite mold was very severe. In the case of BN coating, SiC was formed in the shape of tiny islands at the surface of Si wafer by the reaction between Si-melt and carbon of the graphite mold on the high temperature. The grain size was about 1 mm. The efficiency of Si solar cell was lower than that of Si solar cell fabricated on commercial single and poly crystalline Si wafer. The reason of low efficiency was discussed.

• 한국재료학회지
• /
• 제8권7호
• /
• pp.621-627
• /
• 1998

단결정 Si(100) 기판과 비정질 Si 기판위에 Co/Zr 이중층을 이용하여 형성시킨 Co 실리사이드의 성장 거동에 대하여 연구하였다. 전자빔 증착기를 사용하여 단결정과 비정질 Si 기판위에 Zr $50\AA$과 Co $100\AA$을 차례로 증착한 박막을 50$0^{\circ}C$부터 $800^{\circ}C$까지 $100^{\circ}C$ 간격으로 질소 분위기에서 30초 동안 급속열처리를 하여 Co 실리사이드를 형성시켰다. 각 온도에서 열처리된 시편의 상형성, 화학적 조성, 계면의 형상, 전기적 특성을 XRD, AES, RBS, TEM, HRTEM 등으로 분석하였다. 분석 결과 $CoSi_2$ 상이 단결정 기판에서는 $700^{\circ}C$ 이상에서 기판과 정합성장을 하였고 비정질 기판에서는 다결정 성장을 하였으며 Co 실리사이드의 상형성 온도는 단결정 기판에서보다 비정질 기판에서 $100^{\circ}C$정도 낮아졌다. $CoSi_2$와 같은 Co rich 중간상은 두 기판 모두 형성되지 않았으며 초기 Co 실리사이드의 상형성 온도는 Co 단일층으로 상을 형성시킬 때 보다 더 높았다. Co 실리사이드와 Si 기판의 계면의 형상은 단결정 기판의 경우보다 비정질 기판에서 더 균질하였다. 박막의 면저항은 $600^{\circ}C$이하의 열처리 온도에서는 비정질 기판에서 형성된 Co 실리사이드 박막이 더 낮은 값을 나타내었고 그 이상의 열처리 온도에서는 단결정 기판에서 형성된 박막의 면저항값이 더 낮은 값을 나타내었으며 두가지 기판에서 형성된 박막 모두$ 800^{\circ}C$에서 가장 낮은 면저항 값을 보였다.TEX>$10^{-8}$ A/$\textrm{cm}^2$로 양질의 SrTiO$_3$박막을 제조하였다.는 과정에서 전세계 수준에서 멸종위기 식물을 목록화가 필요하다. 특히, 목록 작업이 완성되면 해당 분류군에 대한 기본적인 자료 수집과 장단기 조사과정으로서, 해당 분류군에 대한 멸종위협 요인을 수집하고, 이 자료를 근간으로 정량적으로 IUCN 적색목록 평가방식이 추진할 필요가 있다.he oscillations are active in the derived unit hydrograph. 3)The parameter estimates are validated by extending the model to the Soyang river Dam site with elimination of the autocorrelation in the disturbances. Finally, this paper illustrates the application of the multiple regression model to drive an optimal unit hydrograph dealing with the multicollinearity and the autocorrelation which cause some problems. 우선적으로 고려하여 사용할 농약을 선택해야 할 것으로 보이나, 그 외 약제의 잔류성, 사용량, 사용시기와 함께 기후조건, 토양의 투수성, 토층이 깊이, 지하수 깊이 등의 지역적인 특성들이 농약의 용탈잠재성에 미치는 영향도 더욱 구체적으로 파악되어야 할 것이며 농약의 선택 과정에서도 이러한 특성들이 앞으로 고려되어야 할 것이다.calenol 및 citrostadienol 등이 함유(含有)되어 있었다. 6. 4-desmethylsterol fraction에 는 sitosterol (74.6%)이

• 한국태양에너지학회:학술대회논문집
• /
• 한국태양에너지학회 2008년도 춘계학술발표대회 논문집
• /
• pp.252-256
• /
• 2008

Photovoltaic (PV) modules output changes noticeable with variations in temperature and irradiance. In general it is has been shown that a $1^{\circ}C$ increase in temperature results in a 0.5% drop in output. In this paper, seven PV module types are analyzed for variation in temperature and irradiance, and the resulting output characteristics examined. The 7 modules types utilized are as follows; 3 poly crystalline modules, 2 single crystalline modules, 1 back contact single crystalline module and 1 HIT module. 3 groups of experiments are then conducted on the modules; tests with varying irradiance values, tests with module temperature varying under $25^{\circ}C$ and tests with module temperature varying over $25^{\circ}C$. The experiments results show that as temperature rises the follow is observed; Pmax decreases by 0.6%, Voc decreases by about 0.4%, and Isc increasing by between 0.03%${\sim}$0.08%. In addition, an irradiance decrease of 100 w/m2 translates into a 10% drop in Pmax.

• Corrosion Science and Technology
• /
• 제9권2호
• /
• pp.81-86
• /
• 2010

The mechanisms of selective oxidation of intercritically annealed CMnAl TRIP steels in a Continuous Galvanizing Line (GCL) were studied by cross-sectional observation of the surface and sub-surface regions by means of High Resolution Transmission Electron Microscopy (HR-TEM). The selective oxidation and nitriding of an intercritically annealed CMnAl TRIP steel in a controlled dew point 10%$H_2+N_2$ atmosphere resulted in the formation of c-xMnO.$MnO_2$ (1${\leq}$x<3) and c-xMnO.$Al_2O_3$ ($x{\geq}1$) particles on the steel surface. Single crystal c-xMnO.$SiO_2$ ($2{\leq}x{\leq}4$) oxide particles were also observed on the surface. A thin film of crystalline c-xMnO.$SiO_2$ (2${\leq}$x<3) and c-xMnO.$Al_2O_3$ ($x{\geq}1$) was present between these particles. In the sub-surface region, internal oxidation, nitriding and intermetallic compound formation were observed. In the first region, large crystalline c-xMnO.$SiO_2$ ($1{\geq}x{\geq}2$) and c-xMnO.$Al_2O_3$ ($x{\geq}1$) oxides particles were present. In the second region, c-AlN particles were observed, and in a third region, small $MnAl_x$ (x>1) intermetallic compound particles were observed.

• 대한전기학회논문지:전기물성ㆍ응용부문C
• /
• 제48권5호
• /
• pp.396-401
• /
• 1999

In this study, $Ar^+$ ion laser etching process of single/poly-crystalline Si with $CCl_2F_2$ gas is investigated for MEMS applications. In general, laser direct etching process is useful in microelectronic process, fabrication of micro sensors and actuators, rapid prototyping, and complementary processing because of the advantages of 3D micromachining, local etching/deposition process, and maskless process with high resolution. In this study, a pyrolytic method, in which $CCl_2F_2$ gasetches molten Si by the focused laser, was used. In order to analyze the temperature profile of Si by the focused laser, the 3D heat conduction equation was analytically solved. In order to investigate the process parameters dependence of etching characteristics, laser power, $CCl_2F_2$ gas pressure, and scanning speed were varied and the experimental results were observed by SEM. The aspect ratio was measured in multiple scanning and the simple 3D structure was fabricated. In addition, the etching characteristics of $6\mum$ thick poly-crystalline Si on the insulator was investigated to obtain flat bottom and vertical side wall for MEMS applications.

• 대한금속재료학회지
• /
• 제46권3호
• /
• pp.159-168
• /
• 2008

Thermally-evaporated 10 nm-Ni/1 nm-Ru/(30 nm or 70 nm-poly)Si structures were fabricated in order to investigate the thermal stability of Ru-inserted nickel monosilicide. The silicide samples underwent rapid thermal anne aling at $300{\sim}1,100^{\circ}C$ for 40 seconds. Silicides suitable for the salicide process were formed on the top of the single crystal and polycrystalline silicon substrates mimicking actives and gates. The sheet resistance was measured using a four-point probe. High resolution X-ray diffraction and Auger depth profiling were used for phase and chemical composition analysis, respectively. Transmission electron microscope and scanning probe microscope(SPM) were used to determine the cross-sectional structure and surface roughness. The silicide, which formed on single crystal silicon and 30 nm polysilicon substrate, could defer the transformation of $Ni_2Si $i and $NiSi_2 $, and was stable at temperatures up to $1,100^{\circ}C$ and $1,100^{\circ}C$, respectively. Regarding microstructure, the nano-size NiSi preferred phase was observed on single crystalline Si substrate, and agglomerate phase was shown on 30 nm-thick polycrystalline Si substrate, respectively. The silicide, formed on 70 nm polysilicon substrate, showed high resistance at temperatures >$700^{\circ}C$ caused by mixed microstructure. Through SPM analysis, we confirmed that the surface roughness increased abruptly on single crystal Si substrate while not changed on polycrystalline substrate. The Ru-inserted nickel monosilicide could maintain a low resistance in wide temperature range and is considered suitable for the nano-thick silicide process.

• 한국세라믹학회지
• /
• 제37권7호
• /
• pp.665-672
• /
• 2000

The ferroelectric YMnO3 thin films were prepared by MOD(metal-organic decomposition) method with Y- and Mn-acetylacetonate as starting materials. Thin films were grown on various substrates by spin-coating technique. The crystalline phases of the thin films were identified by X-ray diffractometer as a function of heat-treatment temperature, pH of coating solution and substrate. In addition, the effect of Mn/Y molar ratio(0.8~1.2) on the formation of hexagonal-YMnO3 phase was investigated. In forming highly c-axisoriented hexagonal-YMnO3 single phase, the Pt coated Si substrate was more effective than the bare Si substrate, and the optimum heat-treatment condition was at 82$0^{\circ}C$ for 30 min. Higher Mn/Y molar ratio within 0.8~1.2 and pH of YMnO3 precursor solution within 0.5~2.5 favored formation of ferroelectric hexagonal phase rather than orthorhombic phase. Leakage current density of the hexagonal-YMnO3 thin film formed on Pt(111)/TiO2/SiO2/Si substrate was low enough as 0.4~4.0$\times$10-8(A/$\textrm{cm}^2$) at 5 V and its remanent polarization(Pr), calculated from the P-E hysteresis loop, was 3 nC/$\textrm{cm}^2$.

• Bulletin of the Korean Chemical Society
• /
• 제25권4호
• /
• pp.480-484
• /
• 2004

$LiGaO_2$ films have been grown on Si (100) substrates using a new single precursor $[Li(OCH_2CH_2OCH_3)_2-Ga(CH_3)_2]_2$ under high vacuum conditions $(5{\times}10^{-6}Torr)$. The $[Li(OCH_2CH_2OCH_3)_2Ga(CH_3)_2]_2$ was synthe-sized and characterized by using spectroscopic methods and single-crystal X-ray diffraction analysis. The chemical composition, crystalline structure, and morphology of the deposited films were investigated by X-ray photoelectron spectroscopy, X-ray diffraction, and scanning electron microscopy. The results show that polycrystalline $LiGaO_2$ films preferentially oriented in the [010] direction can be deposited on Si (100) at 500-550$^{\circ}C$ by metal organic chemical vapor deposition (MOCVD). The single precursor $[LiOCH_2CH_2OCH_3)_2-Ga(CH_3)_2]_2$ has been found suitable for chemical vapor deposition of $LiGaO_2$ thin films on Si substrates.