• 한국전기전자재료학회논문지
• /
• 제11권12호
• /
• pp.1122-1127
• /
• 1998

Group II-AF_2$films such as $CaF_2$, $SrF_2$, and $BaF_2$ have been commonly used many practical applications such as silicon on insulatro(SOI), three-dimensional integrated circuits, buffer layers, and gate dielectrics in filed effect transistor. This paper presents electrical and structural properties of fluoride films as a gate dielectric layer. Conventional gate dielectric materials of TFTs like oxide group exhibited problems on high interface trap charge density($D_it$), and interface state incorporation with O-H bond created by mobile hydrogen and oxygen atoms. To overcome such problems in conventional gate insulators, we have investigated $CaF_2$ films on Si substrates. Fluoride films were deposited using a high vacuum evaporation method on the Si and glass substrate. $CaF_2$ films were preferentially grown in (200) plane direction at room temperature. We were able to achieve a minimum lattice mismatch of 0.74% between Si and $CaF_2$ films. Average roughness of $CaF_2$ films was decreased from 54.1 ${\AA}$ to 8.40 ${\AA}$ as temperature increased form RT and $300^{\circ}C$. Well fabricated MIM device showed breakdown electric field of 1.27 MV/cm and low leakage current of $10^{-10}$ A/$cm^2$. Interface trap charge density between $CaF_2$ film and Si substrate was as low as $1.8{\times}10^{11}cm^{-2}eV^{-1}$.

• 한국전기전자재료학회:학술대회논문집
• /
• 한국전기전자재료학회 2003년도 하계학술대회 논문집 Vol.4 No.1
• /
• pp.139-142
• /
• 2003

Microwave dielectric properties of $Ca(Li_{1/4}Nb_{3/4})O_3-CaTiO_3$ ceramic systems were investigated with calcination temperatures and amounts of $CaTiO_3$ in the range of 0.2 to 0.4mol. $Ca(Li_{1/4}Nb_{3/4})O_3$ ceramics having orthorhombic crystal structure could be synthesized at $750^{\circ}C$ and sintered well at $1250^{\circ}C$. They showed the dielectric constant of 26, quality factor($Q{\times}f_o$) of 13,000 and temperature coefficient of resonant frequency(${\tau}_f$) of $-49{\pm}2ppm/^{\circ}C$ With adding the $CaTiO_3$ amount the dielectric constant and ${\tau}_f$ increased due to the solute of $CaTiO_3$ but the quality factor decreased. The 0.7$Ca(Li_{1/4}Nb_{3/4})O_3-0.3CaTiO_3$ ceramic showed the dielectric constant of 44, quality factor($Q{\times}f_o$) of 12,000 and ${\tau}_f$ of $-9{\pm}1ppm/^{\circ}C$.

• The Korean Journal of Physiology and Pharmacology
• /
• 제14권1호
• /
• pp.51-57
• /
• 2010

It was hypothesized that NaF induces calcium sensitization in $Ca^{2+}$-controlled solution in permeabilized rat mesenteric arteries. Rat mesenteric arteries were permeabilized with $\beta$-escin and subjected to tension measurement. NaF potentiated the concentration-response curves to $Ca^{2+}$ (decreased $EC_{50}$ and increased $E_{max}$). Cumulative addition of NaF (4.0, 8.0 and 16 mM) also increased vascular tension in $Ca^{2+}$-controlled solution at pCa 7.0 or pCa 6.5, but not at pCa 8.0. NaF-induced vasocontraction and $GTP{\gamma}S$-induced vasocontraction were not additive. NaF-induced vasocontraction at pCa 7.0 was inhibited by pretreatment with Rho kinase inhibitors H1152 or Y27632 but not with a MLCK inhibitor ML-7 or a PKC inhibitor Ro31-8220. NaF induces calcium sensitization in a $Ca^{2+}$ dependent manner in $\beta$-escin-permeabilized rat mesenteric arteries. These results suggest that NaF is an activator of the Rho kinase signaling pathway during vascular contraction.

• 한국결정성장학회:학술대회논문집
• /
• 한국결정성장학회 1998년도 PROCEEDINGS OF THE 15TH KACG TECHNICAL MEETING-PACIFIC RIM 3 SATELLITE SYMPOSIUM SESSION 4, HOTEL HYUNDAI, KYONGJU, SEPTEMBER 20-23, 1998
• /
• pp.3-7
• /
• 1998

The rare-earth ions (R3+, R=Nd, Er) doped CaF2 layers have been grown on CaF2(111) substrate by molecular beam epitaxy. The epitaxial relationship and the crystallinity of CaF2:R3+ layers depending on the concentration of R3+ were studied by reflection high-energy electron diffraction (RHEED). In aspect of application as buffer layer in semiconductor-related hybrid structure, the lattice displacement between CaF2:R3+ layers and CaF2(111) substrate was investigated by X-ray rocking curve analysis.

• 한국결정성장학회지
• /
• 제6권4호
• /
• pp.595-599
• /
• 1996

결정입계를 갖는 $CaF_{2}$ 결정을 annealing할 때, 내부에 존재하는 bubbles의 거동을 결정학적으로 분석하였다. 이들 bubbles는 결정 내에서 일어나는 slip 현상처럼 $CaF_{2}$ 결정구조에 의존하여 특정한 방향으로 배향되어 있음이 확인되었다. 또한, AFM(atomic force microscope)으로 분석한 결과, 이들의 움직임은 negative grain growth에 의한 S-surface를 형성하고 있음이 관찰되었다.

• 한국세라믹학회지
• /
• 제48권3호
• /
• pp.246-250
• /
• 2011

Effects on sintering and electrical properties of $La_{0.7}Ca_{0.3}Cr_{0.9}Co_{0.1}O_{3-{\delta}}$ system, a interconnect material for cylindrical and flat tubular solid oxide fuel cells (SOFC), have been investigated by Ca-source when using $CaCO_3$ and $CaF_2$. When using $CaCO_3$ and $CaF_2$ was mixing as Ca-source, single phased perovskite solid solution was observed for each sample. The sintering temperature was decreased by $CaF_2$ contents was increased. When using 0.1 mole $CaF_2$ was densely sintered at $1400^{\circ}C$ and relative density was 93.8%. Also, electrical conductivity in oxidation and reducing atmosphere was 47, 4.3 S/cm, respectively, due to $F^-$ ion enhance the electrical conductivity in reducing atmosphere.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 1999년도 하계학술대회 논문집 D
• /
• pp.1514-1516
• /
• 1999

This paper covers our efforts to improve the low carrier mobility and light instability of hydrogenated amorphous silicon (a-Si:H) films with microcrystalline silicon $({\mu}c-Si)$ films. We successfully prepared ${\mu}c-Si$ films on $CaF_2$/glass substrate by decomposition of $SiH_4$ in RPCVD system. The $CaF_2$ films on glass served as a seed layer for ${\mu}c-Si$ film growth. The XRD analysis on $CaF_2$/glass illustrated a (111) preferred $CaF_2$ grains with the lattice mismatch less than 5 % of Si. We achieved ${\mu}c-Si$ films with a crystalline volume fraction of 61 %, (111) and (220) crystal orientations. grain size of $706\AA$, activation energy of 0.49 eV, and Photo/dark conductivity ratio of 124. By using a $CaF_2$/glass structure. we were able to achieve an improved ${\mu}c-Si$ films at a low substrate temperature of $300^{\circ}C$.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 2003년도 하계학술대회 논문집 C
• /
• pp.1589-1591
• /
• 2003

The microwave dielectric properties of $TiTe_3O_8-CaF_2$ ceramics were investigated. All sample of $TiTe_3O_8-CaF_2$ ceramics were prepared by the conventional mixed oxide method, and sintered in the temperature of $730^{\circ}C{\sim}750^{\circ}C$. The structural properties of $TiTe_3O_8-CaF_2$ ceramics were investigated by the X-ray diffractor meter. According to the X-ray diffraction patterns of $TiTe_3O_8-CaF_2$ ceramics, the major phase of the cubic $TiTe_3O_8$ were presented. In the case of $1molTiTe_3O_8-0.1molCaF_2$ ceramics sintered at $740^{\circ}C$ for 5hr., the bulk density, dielectric constant, quality factor were $2.8g/cm^3$, 39.1, 36.100GHz, respectively.

• 전자공학회논문지D
• /
• 제36D권10호
• /
• pp.31-36
• /
• 1999

질소 화합물의 새로운 형광체를 개발하기 위하여 $CaSiN_2:Eu,\;CaSiN_2:Tb$ 형광체를 합성한 후, 빛 발광 (photoluminescence, PL) 및 전계 발광(electroluminescence, EL) 특성을 평가하였다. $Ca_3N_2$, $Si_3N_4$ 및 $EuF_3$ 또는 $TbF_3$의 미분말을 혼합, 성형 및 소결하여 질소 화합물 형광체를 합성하였다. 합성된 $CaSiN_2:Eu,\;CaSiN_2:Tb$ 형광체의 PL 특성이 각각 Eu, Tb 이온에 의한 고유한 발광 파장과 일치하여 형광체로의 활용 가능성을 확인하였다. 스퍼터링 방법으로 제작된 $CaSiN_2:Eu$ 박막 전계 발광(thin-film electroluminescence, TFEL) 소자의 문턱 전압과 280 V에서의 발광 휘도는 각각 90 V, 1.62 $cd/m^2$ 임을 알 수 있었다. 또한 change-voltage(Q-V) 및 transferred charge-phosphor Field($Q_t-F_p$)의 전기적 특성도 함께 측정되었다.

• 한국결정성장학회지
• /
• 제32권6호
• /
• pp.219-224
• /
• 2022

광학 윈도우, 프리즘, 렌즈 등에 사용되는 CaF₂ 단결정은 3개의 부격자를 가진 face-centered cubic(FCC) 구조를 가지고 있으며 밴드갭(12 eV)이 크고 넓은 파장영역에서 투과율이 우수하고 굴절률이 낮다는 특징이 있다. CaF₂ 단결정 성장은 대표적으로 높은 생산효율과 큰 결정을 만들 수 있는 초크랄스키(Czochralski) 방법으로 생산되고 있다. 이 연구에서는 초크랄스키 방법으로 성장한 일본의 Nikon 사와 미국의 M TI 사 (100)면, (111)면의 CaF₂ 단결정 상용화 웨이퍼의 결정성과 결함밀도를 분석하기 위해 X선 회절(XRD), XRC(X-ray rocking curve) 측정 및 Chemical Etching을 수행하였고 푸리에 변환 적외선 분광법(FT-IR)과 UV-VIS-NIS을 이용하여 CaF₂ 결정의 광학적 특성을 분석하였다. 다양한 분석 결과를 통해 CaF₂ 단결정의 다양한 분야에서의 응용가능성을 체계적으로 살펴보았다.