• Title/Summary/Keyword: $CaF_2$

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Growth of $CaF_{2}:R^{+3}$ (R=Nd, Er) layers by molecular beam epitaxy (Molecular beam epitaxy법에 의한 희토류 이온$(Nd^{3+},\;Er^{3+})$ 첨가 $CaF_{2}$ 박막의 성장)

  • ;Yefen Chen;Tsuguo Fukuda
    • Journal of the Korean Crystal Growth and Crystal Technology
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    • v.9 no.1
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    • pp.1-5
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    • 1999
  • The rare-earth ions ($R^{3+}$, R=Nd, Er) doped $CaF_{2}$ layers have been grown on $CaF_{2}$ (111) substrate by molecular beam epitaxy. The surface structure and the crystallinity of $CaF_{2}:R^{3+}$ layers depending on the doping concentration of $R^{3+}$ and layer thickness 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 $CaF_{2}:R^{3+}$ layers and $CaF_{2}$ (111) substrate was investigated by X-ray rocking curve analysis.

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Optical Characteristics of ZnS/CaF2/ZnS/Cu with Different Optical Thickness of CaF2 Layer (CaF2 두께 변화에 따른 ZnS/CaF2/ZnS/Cu 다층 박막의 광특성)

  • Kim, Jun-Sik;Jang, Gun-Eik
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.22 no.7
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    • pp.584-588
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    • 2009
  • Layered ZnS/$CaF_2$/ZnS/Cu film was deposited on glass substrate by using evaporation method. ZnS and $CaF_2$ were chosen as high and low refractive materials. Cu was used as mid-reflective layer. Reflectance with different optical thickness of $CaF_2$ ranging from $0.25{\lambda}\;to\;0.5{\lambda}$ were systematically investigated by using spectrophotometer. In order to expect the experimental results, the simulation program, the Essential Macleod Program(EMP) was adopted and compared with the experimental data. Based on the results taken by spectrophotometer, the ZnS/$CaF_2$/ZnS/Cu multi-layered thin film show the maximum reflectance of 80% at 625nm $(0.25{\lambda}\;in\;CaF_2)$ and 42% at 660nm $(0.5{\lambda}\;in\;CaF_2)$ respectively. As compared with the experimental results and simulation data, it was confirmed the experimental data is well matched with the EMP data.

Dissociative adsorption and self-assembly of $CaF_2$ on the Si(001)-$4^{\circ}$ off surface

  • Kim, Hui-Dong;Dugerjav, Otgonbayar;Arvishataar, Amarmunkh;Motlak, Moaaed;Seo, Jae-Myeong
    • Proceedings of the Korean Vacuum Society Conference
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    • 2012.02a
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    • pp.132-132
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    • 2012
  • Depositing $CaF_2$[0.6% lattice-mismatch] on the Si(001)-$4^{\circ}$ off surface [composed of a single (001) domain with regularly-arrayed double-layer DB steps and located between (1 1 19) and (1 1 21)] held at $700^{\circ}C$, $CaF_2$ molecules are preferentially adsorbed on the dimers and dissociated to Ca and F atoms. Dissociated Ca atoms form a silicide layer of a $2{\times}3$ structure on the (001) terrace, while F atoms are desorbed from the surface. Once the terrace is covered with a calcium silicide layer, CaF starts to be adsorbed selectively on the steps, as shown in Fig. (a). With $CaF_2$ deposition exceeding 1 ML, the (1 1 17) surface having 1-D $CaF_2$ nanodots are formed as shown in Fig. (b). By the present STM study, it has been clearly disclosed that the calcium silicide interfacial layer is preformed prior to adsorption of $CaF_2$ on vicinal Si(001) surface.

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Behavior of $CaF_2$ at the Initial Adsorption Stage on Si(114)

  • Dugerjav, Otgonbayar;Duvjir, Ganbat;Li, Huiting;Kim, Hui-Dong;Seo, Jae-Myeong
    • Proceedings of the Korean Vacuum Society Conference
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    • 2012.02a
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    • pp.242-242
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    • 2012
  • From the combined studies of STM and synchrotron photoemission, it has been found that a $CaF_2$ molecule is dissociated to Ca and F atoms on the $Si(114)-2{\times}1$ held at $500^{\circ}C$ at the initial adsorption stage. The Ca atoms form isolated and unique shapes of silicide molecules as shown in Fig. (a), while the F atoms are desorbed from the surface. On the other hand, beyond a $CaF_2$ coverage of 0.3 monolayer, as shown in Fig. (b), in addition to these silicide molecules, a 1-D facet [composed of (113) and (115) faces] adjacent to an etch pit has been observed, and F atoms are also detected from photoemission. These results imply that F atoms act as an etchant on Si(114) and CaF is adsorbed selectively on the (113) face of this facet. From the present studies, it has been concluded that, an insulating $CaF_2$ layer like that on Si(111) cannot be formed on Si(114), but a CaF-decorated nanofacet with a high aspect-ratio can be grown.

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High Frequency Dielectric Properties of $CaF_2$ filled Glass-Composites ($CaF_2$가 Filler로 첨가된 유리복합체의 고주파 유전특성)

  • Kim, Sun-Young;Lee, Kyoung-Ho;Kim, Sung-Won
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2003.05c
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    • pp.277-281
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    • 2003
  • Effects of $CaF_2$ addition as a filler on the high frequency dielectric properties and sintering of CaO-$Al_2O_3-SiO_2-B_2O_3$(CASB) and ZnO-MgO-$B_2O_3-SiO_2$(ZMBS) glass composites were investigated. The optimal glass composition in the CASB system was 33.0CaO-$17.0Al_2O_3-35.0SiO_2-15.0B_O_3$(in wt%). The corresponding dielectric properties were k=8.1 and $Q{\times}fo$=1,200GHz. The sintering temperature was $800{\mu}m$. In case of 2MBS system, 25.0ZnO-25.0MgO-20.0$B_2O_3-30.0SiO_2$(in wt%) glass showed k=6.8 and $Q{\times}fo$=5,200GHz when it was sintered at $750^{\circ}C$. The maximum amount of $CaF_2$ in the CASB and 2MBS glass system without any detrimental effect on the sintering was 25.0 v/o and 15.0 v/o, respectively. The addition of $CaF_2$ in the glass systems improved the high frequency dielectric properties. In case of CASB+$CaF_2$ composite, k was 7.1 and $Q{\times}fo$ was 2,300GHz. And in case of 2MBS+$CaF_2$ composite, k was 5.9 and $Q{\times}fo$ was 8,100GHz. $CaF_2$ addition also reduced sintering temperature. Effects of $CaF_2$ on the dielectric and sintering properties was analyzed in terms of viscosity and crystallization behavior changes due to the interaction between $CaF_2$ and the glass systems.

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Recovery of An, Ag, and Ni from PCB Wastes by CaF2-containing Slag (형우(螢右) 함유(含有) 슬래그 노이(盧理)를 통한 PCB 스크랩으로부터 Au, Ag, Ni의 회수(回收)에 관한 연구(班究))

  • Park, Joo-Hyun
    • Resources Recycling
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    • v.20 no.4
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    • pp.58-64
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    • 2011
  • Recovery of novel metals such as Au, Ag and Ni from wastes PCB was investigated by slag treatments. The CaO-$Al_2O_3$(-$SiO_2$) and CaO-$SiO_2$-$CaF_2$ slags were employed in the present study. The PCB/Cu ratio is recommended to be lower than unity. The use of CaO-$SiO_2$-$CaF_2$ slag provided the more higher yield of Au, Ag and Ni than the CaO-$Al_2O_3$(-$SiO_2$) slag did, which was mainly due to the lower melting point and the viscosity of $CaF_2$-containing slag. The terminal descending velocity of metal droplets in the slag phase increased with decreasing slag viscosity.

A study on the electrolytic properties of $CaF_2$ crystals with $YF_3$ addition ($YF_3 $ 첨가에 따른 $CaF_2 $ 결정의 고체전해질 특성에 관한 연구)

  • Cha, Y.W.;Park, D.C.;Orr, K.K.
    • Journal of the Korean Crystal Growth and Crystal Technology
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    • v.4 no.1
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    • pp.21-32
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    • 1994
  • $CaF_2$ crystals were grown with various growth rates by Bridgman method, and the electrical properties of these were studied to examine the changes of ionic conductivities with growth rates by AC Impedance Analyzer. As the growth rates were higher, $CaF_2$ crystals were grown to polycrystals from single crystal. And as grain boundaries and various defects were altered, the ionic conductivities were changed dramatically. $YF_3$ added to $CaF_2$ for disorderizing $CaF_2$ structure and improving the number of $F^-$ carriers and vacancies in $CaF_2$ crystals. Then $Ca_{1-x}Y_XF_{2+X}$ crystals were gained. And the ionic conductivities of $Ca_{1-x}Y_XF_{2+X}$ crystals were investigated with $YF_3$ addition. The ionic conductivities of $CaF_2$ and $Ca_{1-x}Y_XF_{2+X}$ crystals with temperatures were compared. In addition, the effects of clusterings and defects on the electrical properties of solid electrolytes were researched.

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Extraction of Aluminum from Coal Fly Ash with Sulfuric Acid and Calcium Fluoride (석탄 비산회로부터 황산과 $CaF_2$에 의한 알루미늄의 추출)

  • 구현정;이재천;윤인주;정진기;임남웅
    • Resources Recycling
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    • v.6 no.1
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    • pp.11-16
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    • 1997
  • The extraction of aluminum from coal fly nsh wa studied using H,SO, and CaF, as leachants Aluminum was effectively extracted by HF formed &om the reaction of H,SO, and CaF, which decomposed the mullite in fly ash. The cffeas of H,SO' and CaFi concentration, reaction temperature, and reacliou time on aluminum extraction were investigated. 97% of aluminum was extracted by 4 M H:SO, and 0.5 M CaF, at 106$^{\circ}$C for 10 houci.

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Free Energy of Formation of BaThO3 from E.M.F. Measurement

  • Park, S. H.;H. D. Baek;J. S. Hwang;Park, C. O.
    • The Korean Journal of Ceramics
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    • v.4 no.3
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    • pp.204-206
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    • 1998
  • The Gibbs free energy of formation of $BaThO_3$ from elemental oxides has been measured at temperatures between 853 and 903 K using a $CaF_2$ solid electrolyte galvanic cell. The galvanic cell consisted of Pt, $O_2, CaO+CaF_2 \parallel CaF_2 \parallelBaThO_3+ThO_2+BaF_2, O_2$, Pt EMF gave the standard Gibbs free energy for the reaction $CaF_2+BaThO_3=CaO+BaF_2+ThO_3$ as $\DeltaG^o$,/TEX>=124111.031-117.597 T(J/mol).

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Eelctrical and Structural Properties of $CaF_2$Films ($CaF_2$ 박막의 전기적, 구조적 특성)

  • 김도영;최석원;이준신
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.11 no.12
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    • pp.1122-1127
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    • 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 $1.8{\times}10^{11}cm^{-2}eV^{-1}$.

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