• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.13 no.11
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• pp.959-962
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• 2000

We have fabricated good quality superconducting YBa$_2$Cu$_3$$O_{7-x}$(YBCO) thin films on Hastelloy(Ni-Cr-Mo alloys) metallic substrates with CeO$_2$and BaTiO$_3$buffer layers in-situ by pulsed laser deposition in a multi-target processing chamber. YBCO film with CeO$_2$single buffer layer shows T$_{c}$ of 71.64 K and the grain size less than 0.1${\mu}{\textrm}{m}$. When BaTiO$_3$ is used as a single buffer layer, the grain size of YBCO is observed to be larger than that of YBCO/CeO$_2$by 200 times and the transition temperature of the film is enhanced to be about 84 K. CeO$_2$/BaTiO$_3$double buffer layer has been adopted to enhance the superconducting properties, which results in the enhancement of the critical temperature and the critical current density to be about 85 K and 8.4$\times$10$^4$ A/$\textrm{cm}^2$ at 77 K, respectively mainly due to the enlargement of the grain size of YBCO film.ilm.

• Progress in Superconductivity and Cryogenics
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• v.6 no.4
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• pp.1-4
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• 2004

Three group samples with difference thickness of $CeO_2$ capping layer deposited by PLD were studied. Among them, one group $CeO_2$ films were deposited on stainless steel tape coated with IBAD- YSZ and $CeO_2$ buffer layer ($CeO_2$/IBAD-YSZ/SS); other two groups of $CeO_2 YSZ Y_2O_3$multi-layer were deposited on NiW substrates for fabrication of YBCO coated conductor through RABiTS approach. The pulsed laser deposition (PLD) and DC magnetron sputtering were employed to deposit these buffer layers. On the top of buffer layer, YBCO film was deposited by PLD. The effect of thickness of $CeO_2$ film on the texture of $CeO_2$ film and critical current density ($J_c$) of YBCO film were analyzed. For the case $CeO_2$ on $CeO_2$/IBAD-YSZ/SS, there was a self-epitaxy effect with the increase of $CeO_2$ film. For $YSZ/Y_2O_3$ NiW which was deposited by PLD or DC magnetron sputtering, there is not self-epitaxy effect. However, the capping layer of $CeO_2$ film deposited by PLD improved the quality of buffer layer for $YSZ/Y_2O_3$ which was deposited by DC magnetron sputtering, therefore increased the $J_c$ of YBCO film.

• Progress in Superconductivity
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• v.7 no.2
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• pp.120-129
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• 2006

We comparatively studied the epitaxial growth conditions of $CeO_2$ and $Y_2O_3$ thin buffers on textured Ni tapes using rf magnetron sputtering and investigated the feasibility of getting a single mixture layer or sequential layers of $CeO_2$ and $Y_2O_3$ for more simplified buffer architecture. All the buffer layers were first deposited using the reducing gas of $Ar/4%H_2$ and subsequently the reactive gas mixture of Ar and $O_2$, The crystalline quality and biaxial alignment of the films were investigated using X-ray diffraction techniques (${\Theta}-2{\Theta},\;{\phi}\;and\;{\omega}\;scans$, pole figures). The $CeO_2$ single layer exhibited well developed (200) epitaxial growth at the condition of $10%\;O_2$ below an $450^{\circ}C$, but the epitaxial property was decreased with increasing the layer thickness. $Y_2O_3$ seldom showed optimum condition for (400) epitaxial growth. The sequential architecture of $CeO_2/Y_2O_3/CeO_2$ having good epitaxial property was achieved by sputtering at a temperature of $700^{\circ}C$ on the initial $CeO_2$ bottom layer sputtered at $400^{\circ}C$. Cracking of the sputtered buffer layers was seldom observed except the double layer structure of $CeO_2/Y_2O_3$.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.06a
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• pp.261-262
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• 2006

High temperature superconducting coated conductor has multi-layer structure of protecting layer/superconducting layer/buffer layer/metallic substrate. The buffer layer consists of multi layer, and the architecture most widely used in RABiTS approach is $CeO_2$(cap layer)/YSZ(diffusion barrier layer)/$CeO_2$(seed layer). Multi-buffer layer deposition required many times and process. Therefore single buffer layer deposition study reduce 2G HTS manufacture efforts. Evaporation technique for single buffer deposition method is used for the $CeO_2$ layer. $CeO_2$ single buffer film could be achieved in the chamber. Detailed deposition conditions (temperature and partial gas pressure of deposition) were investigated for the rapid growth of high quality $CeO_2$ single buffer film.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.16 no.10
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• pp.865-870
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• 2003

The MFIS (Metal-Ferroelectric-Insulator-Semiconductor) capacitors were fabricated using a metalorganic decomposition method. Thin layers of CeO$_2$ were deposited as a buffer layer on Si substrate and BLT thin films were used as a ferroelectric layer. The electrical and structural properties of the MFIS structure were investigated. X -ray diffraction was used to determine the phase of the BLT thin films and the quality of the CeO$_2$ layer. The morphology of films and the interface structures of the BLT and the CeO$_2$ layers were investigated by scanning electron microscopy. The width of the memory window in the C-V curves for the MFIS structure is 2.82 V. The experimental results show that the BLT-based MFIS structure is suitable for non-volatile memory FETs with large memory window.

• Progress in Superconductivity and Cryogenics
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• v.8 no.4
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• pp.8-11
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• 2006

High temperature superconducting coated conductor has various buffer structures on Ni-W alloy. We comparatively studied the growth conditions of a multi buffer layer $(CeO_2/YSZ/CeO_2)$ and a single buffer layer$(CeO_2)$ on textured Ni-W alloy tapes. XRD data showed that the qualities of in-plane and out-of-plane textures of the two type buffer structures were good. Also, we investigated the properties of SmBCO superconducting layer that was deposited on the two type buffer structure. The SmBCO superconducting properties on the single and multi buffer structure showed different critical current values and surface morphologies. FWHM of In-plane and out-of-plane textures were $7.4^{\circ},\;5.0^{\circ}$ in the top CeO2 layer of the multi-buffer layers of $CeO_2/YSZ/CeO_2$, and $7.3^{\circ},\;5.1^{\circ}$ in the $CeO_2$ single buffer layer. $1{\mu}m-thick$ SmBCO superconducting layers were deposited on two type buffer layer. $I_c$ of SmBCO deposited on single and multi buffer were 90 A/cm, 150 A/cm and corresponding $J_c$ were $0.9MA/cm^2,\;1.5MA/cm^2$ at 77K in self-field, respectively.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.07a
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• pp.790-793
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• 2000

We have fabricated good quality superconducting YBa$_2$Cu$_3$$O_{7-x}$(YBCO) thin films on Hastelloy(Ni-Cr-Mo alloys) metallic substrates with CeO$_2$and BaTiO$_3$buffer layers in-situ by pulsed laser deposition in a multi-target processing chamber. YBCO film with CeO$_2$ single buffer layer shows T$_{c}$ of 71.64 K and the grain size less than 0.1 ${\mu}{\textrm}{m}$. When BaTiO$_3$is used as a single buffer layer, the grain size of YBCO is observed to be larger than that of YBCO/CeO$_2$by 200 times and the transition temperature of the film is enhanced to be about 84 K. CeO$_2$/BaTiO$_3$double buffer layer has been adopted to enhance the superconducting properties, which results in the enhancement of the critical temperature and the critical current density to be about 85 K and 8.4 $\times$ 10$^4$ A/cm$^2$ at 77 K, respectively mainly due to the enlargement of the grain size of YBCO film.ilm.

• Proceedings of the KIEE Conference
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• 1999.11d
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• pp.873-875
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• 1999

We have fabricated good quality superconducting $YBa_{2}Cu_{3}O_{7-\delta}$ thin films on Hastelloy(Ni-Cr-Mo alloys) metallic substrate with $CeO_2$ and $BaTiO_3$ buffer layers in-situ by pulsed laser deposition in a multi-target processing chamber. We have chosen $CeO_2$ as a buffer layer which has cubic structure of $5.41{\AA}$ lattice parameter and only 0.2% of lattice mismatch with YBCO. $CeO_2$ layer may be helpful for power transmission due to its conducting property. In order to enhance the crystallization of YBCO films on metallic substrates. we deposited $CeO_2$ and $BaTiO_3$ buffer layers at various temperatures. The YBCO superconducting tape fabricated with $BaTiO_3$ and $CeO_2$ buffer layers shows 85K of transition temperature and about $8.4{\times}10^4A/cm^2$ of critical current density at 77K.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1999.05a
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• pp.469-472
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• 1999

CeO$_2$ thin films have used in wide applications such as SOI, buffer layer, antirflection coating, and gate dielectric layer. CeO$_2$takes one of the cubic system of fluorite structure and shows similar lattice constant (a=0.541nm) to silicon (a=0.543nm). We investigated CeO$_2$films as buffer layer material for nonvolatile memory device application of a single transistor. Aiming at the single transistor FRAM device with a gate region configuration of PZT/CeO$_2$ /P-Si , this paper focused on CeO$_2$-Si interface properties. CeO$_2$ films were grown on P-type Si(100) substrates by 13.56MHz RF magnetron sputtering system using a 2 inch Ce metal target. To characterize the CeO$_2$ films, we employed an XRD, AFM, C-V, and I-V for structural, surface morphological, and electrical property investigations, respectively. This paper demonstrates the best lattice mismatch as low as 0.2 % and average surface roughness down to 6.8 $\AA$. MIS structure of CeO$_2$ shows that breakdown electric field of 1.2 MV/cm, dielectric constant around 13.6 at growth temperature of 200 $^{\circ}C$, and interface state densities as low as 1.84$\times$10$^{11}$ cm $^{-1}$ eV$^{-1}$ . We probes the material properties of CeO$_2$ films for a buffer layer of FRAM applications.

• 한국초전도학회:학술대회논문집
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• v.9
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• pp.142-146
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• 1999

CeO$_2$ buffer layers and in-situ YSa$_2Cu_3O_{7-{\delta}}$ (YBCO) thin films were grown by pulsed laser deposition method on R-plane sapphire substrates. Superconducting properties and surface morphologies of YBCO thin films exhibit strong dependence on the crystallinity of CeO$_2$ buffer layer. The best a-axis oriented CeO$_2$ buffer layers could be grown at 800 $^{\circ}C$ of deposition temperature, 1.5 J/ cm$^2$ of laser energy density and 50 mTorr of oxygen pressure. The YBCO thin films on the a-axis CeO$_2$ buffer layer have Tc (R=0) ${\ge}$ 89.5 K, ${\delta}$Tc ${\sim}$ 0.5 K, and Jc ${\ge}$ 3.2 ${\times}$ 10$^6$ A/ cm$^2$ at 77 K.