• 한국결정성장학회지
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• 제7권2호
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• pp.197-206
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• 1997

6H-SiC 위에 SiC 에피층이 화학 기상 증착(CVD)에 의하여 성장되었다. 성장된 SiC 에피층의 결정구조는 X-선 회절과 Raman 분광을 사용하여 조사되었으며, 이 에피층은 6H-SiC로서 성장되었음을 확인하였다. 수정된 Lely법으로 성장된 한 SiC 결정 분말의 결정구조를 확인하기 위하여 전형적인 SiC polytype들의 X-선 회절상을 계산하였으며, 측정된 X-선 회절상과 비교하여 이 SiC 결정에는 15R-SiC가 약간 혼재되어 있음을 확인하였다.

• Macromolecular Research
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• 제17권2호
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• pp.104-109
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• 2009

Solid-state facilitated, olefin transport membranes were prepared by complexation of poly(styrene-b-iso-prene-b-styrene) (SIS) block copolymer and silver salt. Facilitated olefin transport was not observed up to a silver mole fraction of 0.14, representing a threshold concentration, above which transport increased almost linearly with increasing silver salt concentration. This was because firstly the silver ions were selectively coordinated with the C=C bonds of PI blocks up to a silver mole fraction of 0.20, and secondly the coordinative interaction of the silver ions with the aliphatic C=C bond was stronger than that with the aromatic C=C bond, as confirmed by FT-Raman spectroscopy. Small angle X-ray scattering (SAXS) analysis showed that the cylindrical morphology of the neat SIS block copolymer was changed to a disordered structure at low silver concentrations ($0.01{\sim}0.02$). However, at intermediate silver concentrations ($0.15{\sim}0.20$), disordered-ordered structural changes occurred and finally returned to a disordered structure again at higher silver concentrations (>0.33). These results demonstrated that the facilitated olefin transport of SIS/silver salt complex membrancs was significantly affected by their coordinative interactions and nano-structural morphology.

• Journal of Magnetics
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• 제19권4호
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• pp.333-339
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• 2014

Single crystal growth of $BaFe_{12}O_{19}$ by the solid state crystal growth method was attempted. Seed crystals of ${\alpha}-Fe_2O_3$ were pressed into pellets of $BaFe_{12}O_{19}$ + 2 wt% $BaCO_3$ and heat-treated at temperatures between $1150^{\circ}C$ and $1250^{\circ}C$ for up to 100 hours. Instead of single crystal growth taking place on the seed crystal, BaO diffused into the seed crystal and reacted with it to form a polycrystalline reaction layer of $BaFe_{12}O_{19}$. The microstructure, chemical composition and structure of the reaction layer were studied using scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS), x-ray Diffraction (XRD) and micro-Raman scattering and confirmed to be that of $BaFe_{12}O_{19}$. XRD showed that the reaction layer shows a strong degree of orientation in the (h00)/(hk0) planes in the sample sintered at $1200^{\circ}C$. $BaFe_{12}O_{19}$ layers with a degree of orientation in the (hk0) planes could also be grown by heat-treating an ${\alpha}-Fe_2O_3$ seed crystal buried in $BaCO_3$ powder.

• 한국정보통신학회논문지
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• 제7권5호
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• pp.1032-1037
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• 2003

보론 도핑된 CdS 박막을 chemical bath deposition법으로 증착하고, 도핑농도에 따른 박막의 구조적, 광학적 특성을 조사하였다. 보론 도핑된 CdS 박막은 XRD 분석 결과 (002)면 방향으로 강한 우선성장 방위를 가지며 육방정(hexagonal) 구조로 성장하였다 보론 도핑에 관계없이 모든 시편은 2.3 eV(녹색 발광) 및 1.6 eV(적색 발광) 부근에서 PL peak을 가지며, 도핑 농도가 증가함에 따라 피크 세기는 감소하였다. 보론 도핑에 따라 CdS 박막의 가시광 영역에서의 광투과율은 향상되었고, 밴드 갭은 증가하였다.

• 한국광물학회지
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• 제30권2호
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• pp.59-70
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• 2017

$SiO_2$는 지각과 맨틀을 구성하는 풍부한 물질로 고압 상태의 $SiO_2$ 원자구조를 결정짓는 전자구조적 특성에 대한 상세한 이해는 지구 내부의 탄성과 열역학적 성질에 대한 통찰을 제공한다. $SiO_2$처럼 경원소(low-z)로 이루어진 지구 물질의 고압상 전자구조는 in situ 고압 XRS (x-ray Raman scattering) 실험을 통해 연구되어 왔다. 하지만 기존의 고압 실험 방법으로는 물질의 국소 원자구조와 XRS 스펙트럼 간 상관관계를 밝히는데 한계가 있다. 이를 극복하고 더 높은 압력에서 존재하는 $SiO_2$에 대한 XRS 정보를 얻기 위해 밀도 범함수 이론(density functional theory; DFT)에 기반을 둔 제1원리(ab initio) 계산법을 이용한 XRS 스펙트럼 계산 연구들이 진행되고 있다. 비탄성 X-선 산란에 의하여 원자핵 주변 1s 오비탈에 만들어지는 전자-정공(core-hole)은 경원소 물질의 국소 전자구조에 크게 영향을 미치기 때문에 O K-edge XRS 스펙트럼 형태를 계산할 때 중요하게 고려해야 한다. 본 연구에서는 온-퍼텐셜 선형보충파(full-potential linearized augmented plane wave; FP-LAPW) 방법론에 기반하는 WIEN2k 프로그램을 사용하여 ${\alpha}-quartz$, ${\alpha}-cristobalite$ 그리고 $CaCl_2$-구조를 갖는 $SiO_2$에 대한 O 원자 전자 오비탈의 부분 상태밀도(partial density of states; PDOS)와 O K-edge XRS 스펙트럼을 계산하였다. 또한, $CaCl_2$-구조를 갖는 $SiO_2$의 O 원자 PDOS의 전자-정공 효과의 적용 여부에 따른 차이를 비교하여, 원자핵 부근 전자구조 변화에 따른 PDOS의 피크 세기와 위치 변화가 크게 나타났다는 사실을 확인할 수 있었다. 또한 계산된 각 $SiO_2$ 구조의 O K-edge XRS 스펙트럼이 각 $SiO_2$ 구조에서 계산된 O 원자의 $p^*$ 오비탈의 PDOS 결과와 매우 유사한 형태를 갖고 있음을 확인하였다. 이는 O K-edge XRS 스펙트럼이 갖는 대부분의 특징적인 피크들이 O 원자의 점유 1s 오비탈에서 $2p^*$ 오비탈로의 전자전이에 기인하기 때문이다. 본 연구의 결과는 $SiO_2$에 대한 정확한 O K-edge XRS 스펙트럼을 계산하는데 있어 전자-정공 효과를 고려해야 한다는 사실을 보여준다. 또한, 실험적으로는 재현이 어려운 고압 환경에 존재하는 $CaCl_2$-구조를 갖는 $SiO_2$ (~63 GPa)에 대한 O K-edge XRS 스펙트럼 계산을 통해, 제1원리 계산이 고압상 물질의 물성 연구에 이용될 수 있다는 사실을 보여준다.

• 한국전기전자재료학회논문지
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• 제19권8호
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• pp.732-736
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• 2006

This paper describes the physical characterizations of polycrystalline 3C-SiC thin films heteroepitaxially grown on Si wafers with thermal oxide, In this work, the 3C-SiC film was deposited by LPCVD (low pressure chemical vapor deposition) method using single precursor 1, 3-disilabutane $(DSB:\;H_3Si-CH_2-SiH_2-CH_3)\;at\;850^{\circ}C$. The crystallinity of the 3C-SiC thin film was analyzed by XPS (X-ray photoelectron spectroscopy), XRD (X-ray diffraction) and FT-IR (fourier transform-infrared spectometers), respectively. The surface morphology was also observed by AFM (atomic force microscopy) and voids or dislocations between SiC and $SiO_2$ were measured by SEM (scanning electron microscope). Finally, residual strain was investigated by Raman scattering and a peak of the energy level was less than other type SiC films, From these results, the grown poly 3C-SiC thin film is very good crystalline quality, surface like mirror, and low defect and strain. Therefore, the polycrystalline 3C-SiC is suitable for harsh environment MEMS (Micro-Electro-Mechanical-Systems) applications.

• Bulletin of the Korean Chemical Society
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• 제28권4호
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• pp.533-537
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• 2007

This paper describes the heteroepitaxial growth of single-crystalline 3C-SiC (cubic silicon carbide) thin films on Si (100) wafers by atmospheric pressure chemical vapor deposition (APCVD) at 1350 oC for micro/nanoelectromechanical system (M/NEMS) applications, in which hexamethyldisilane (HMDS, Si2(CH3)6) was used as a safe organosilane single-source precursor. The HMDS flow rate was 0.5 sccm and the H2 carrier gas flow rate was 2.5 slm. The HMDS flow rate was important in obtaing a mirror-like crystalline surface. The growth rate of the 3C-SiC film in this work was 4.3 μm/h. A 3C-SiC epitaxial film grown on the Si (100) substrate was characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), reflection high energy electron diffraction (RHEED), atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS) and Raman scattering, respectively. These results show that the main chemical components of the grown film were single-crystalline 3C-SiC layers. The 3C-SiC film had a very good crystal quality without twins, defects or dislocations, and a very low residual stress.

• Transactions on Electrical and Electronic Materials
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• 제9권5호
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• pp.209-212
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• 2008

We developed a simple and effective purification method to obtain high-purity single-walled carbon nanotubes (SWCNTs) with low surface damage. The purification process consists of oxidization at $430^{\circ}C$ for 1 h in a furnace system of air atmosphere and homogenization in dilute hydrochloric acid solution for extremely short time. The role of homogenizer was examined during purification process in terms of purity and quality of purified SWCNTs. High-purity and low surface damage of SWCNT products was obtained using homogenizer which was operated at 8500 rpm for 10 min in the environment of 7 % HCI solution. From XRD spectra, we observed that metal catalysts were thoroughly removed. Raman spectra showed that the intensity values of crystallization ($I_{G}/I_{D}$) of purified SWCNTs were very similar with that of pristine SWCNTs. Moreover, the structure damage of purified SWCNTs was hard to find from electron microscopy. Consequently, homogenizing, which is a quick and simple manner, can be promising method for obtaining final SWCNTs with clearly high purity and crystallinity.

• 한국전기전자재료학회논문지
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• 제32권6호
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• pp.458-461
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• 2019

The facile synthesis of shape-controlled Pd nanoparticles (PdNPs) with ascorbic acid as a reducing agent and cetyltrimethylammonium bromide (CTAB) as a capping agent is presented in this study. The synthesized PdNPs were characterized by UV-vis spectroscopy, transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray diffraction (XRD), and Raman Spectroscopy. The prepared PdNPs show efficient surface-enhanced Raman scattering (SERS) properties. SERS studies on the adsorption characteristics of 1,4-phenylene diisocyanide (1,4-PDI) on colloidal PdNPs have revealed that the relative peak intensity of the $(NC)_{free}$ and $(NC)_{bound}$ modes distinctly depends on the 1,4-PDI concentration as well as the shape of the PdNPs. Furthermore, we found that the PdNPs are also efficient photoelectron emitters such that the SERS spectrum of 4-nitrobenzenethiol (4-NBT) on PdNPs is readily converted to that of 4-aminobenzenethiol (4-ABT) under 632.8 nm radiation.

• Journal of Korean Vacuum Science & Technology
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• 제6권2호
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• pp.71-75
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• 2002

GaAs polycrystalline thin films with good performance were prepared on conducting glass by hot wall epitaxy (HWE), which were used for solar cell. Electron probe micro-analyzer (EPMA) was applied for the composition, morphology of surface and cross-section of grown films, and X-ray diffraction (XRD) for their phase structure; Raman scattering spectum (RSS) and photoluminescence (PL) were used for evaluating their optical characteristics. The results show that, there is textured structure on the surface of grown GaAs polycrystalline films, which is greatly promised to be suitable for the candidate of solar cell with low cost and high efficiency. It is concluded that the source and substrate at temperature of 900 ~ 930 $\^{C}$ and 500 $\^{C}$ respectively would be beneficial for such films.