• Journal of the Korean Crystal Growth and Crystal Technology
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• v.8 no.4
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• pp.599-604
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• 1998

We have investigated Pt and $RuO_2$ as a bottom electrode for ferroelectric capacitor applications. The bottom electrodes were prepared by using an RF magnetron sputtering method. Some of the investigated parameters were a substrate temperature, gas flow rate, RF power for the film growth, and post annealing effect. The substrate temperature strongly influenced the surface morphology and resistivity of the bottom electrodes as well as the film crystallographic structure. XRD results on Pt films showed a mixed phase of (111) and (200) peak for the substrate temperature ranged from RT to $200^{\circ}C$, and a preferred (111) orientation for $300^{\circ}C$. From the XRD and AFM results, we recommend the substrate temperature of $300^{\circ}C$ and RF power 80W for the Pt bottom electrode growth. With the variation of an oxygen partial pressure from 0 to 50%, we learned that only Ru metal was grown with 0~5% of $O_2$ gas, mixed phase of Ru and $RuO_2$ for $O_ 2$ partial pressure between 10~40%, and a pure $RuO_2$ phase with $O_2$ partial pressure of 50%. This result indicates that a double layer of $RuO_2/Ru$ can be grown in a process with the modulation of gas flow rate. Double layer structure is expected to reduce the fatigue problem while keeping a low electrical resistivity. As post anneal temperature was increased from RT to $700^{\circ}C$, the resistivity of Pt and $RuO_2$ was decreased linearly. This paper presents the optimized process conditions of the bottom electrodes for memory device applications.

• Journal of the Korean Vacuum Society
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• v.8 no.3B
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• pp.322-326
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• 1999

We have investigated the growing process of a silicon film on the $CeO_2/Si$ surface. The silicon was deposited by using electron beam deposition method. The $CeO_2$(111) film was grown on a (111)-oriented silicon substrate at $700^{\circ}C$ at oxygen [partial pressure of $5\times10^{-5}$ Torr. To investigate the condition of epitaxial growth of si films on the $CeO_2/Si$ substrate, we deposited Si at various temperature니 The overlayer silicon was characterized by using x-ray diffraction(XRD). double crystal x-ray diffraction (DCXRD), and transmission electron microscopy (TEM). At temperature higher than $690^{\circ}C$, $CeO_2$ layer was observed at the $CeO_2/Si$ interface, which was formed by chemical reaction with silicon and oxygen dissociated from $CeO_2$. When silicon was deposited on the $CeO_2/Si$ at $620^{\circ}C$, silicon grew epitaxially along the (111)-direction.

• The Korean Journal of Ceramics
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• v.4 no.2
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• pp.141-145
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• 1998

The electrical properties of the mixed conducting yttria(8 mol%) stabilized zirconia(YSZ)-nickel oxide(NiO) composites were examined by a.c. impedance, 4-probe d.c. conductivity between 400 and $1000^{\circ}C$. The oxygen partial pressure dependence of conductivity, and electromotive force measurement of galvanic cell enabled to determine the electronic contribution to the conduction. Up to 6 vol% NiO addition, the conductivity decreased since the electronic NiO acted as an insulator in ionic matrix. However the ionic transport was dominant until NiO content reaches 26 vol%. Mixed conduction was observed between 26 and 68 vol% of NiO. The effect of composition on the electrical property was explained by the microstructure and thus by the distribution of two phases.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2010.06a
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• pp.370-370
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• 2010

The effects of adding higher-valence impurities on the bipolar resistive switching characteristics of Pt/$NiO_{1+x}$/TiN MIM stacks and physical properties were investigated. $NiO_{1+x}$ films with 14% W deposited at 20% oxygen partial pressure exhibited the bipolar resistance switching characteristics in Pt/$NiO_{1+x}$/TiN MIM stacks, while $NiO_{1+x}$ films with 8.2% W show unipolar resistance switching behavior. The relationship of W-doping and the crystallinity was studied by X-ray diffraction. The metallic Ni contents and $WO_x$ binding states with W amount was investigated by XPS. Our result showed that the metallic Ni, $WO_x$ binding states, and crystallinity in $NiO_{1+x}$ played an important role on the bipolar resistive switching.

• Journal of the Korean institute of surface engineering
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• v.40 no.1
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• pp.39-43
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• 2007

The pure CrN powders oxidized to $Cr_2O_3$ noticeably above $850^{\circ}C$ in air. When these powders were sintered into bulk samples at $1500^{\circ}C$ under 40 atm of $N_2$ pressure, the CrN phase partly changed into the $Cr_2N$ phase, owing to the partial loss of nitrogen from CrN. When the bulk sample was heated at $1000-1200^{\circ}C$ for 100 hr under vacuum, the CrN phase also progressively changed into $Cr_2N$. At the same time, a relatively thin $Cr_2O_3$ layer formed on the bulk sample due to the reaction of chromium with residual oxygen in vacuum.

• Transactions of the Korean hydrogen and new energy society
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• v.18 no.4
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• pp.356-364
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• 2007

The partial reduction and water splitting properties of metal substituted ferrite mediums for two-step thermochemical hydrogen production, were carried out by TPR/O(Temperature programmed reduction/oxidation) method at a temperature of below 1173 K and under atmospheric pressure. $ZrO_2$ was added to the ferrite as a binder to prevent the sintering. As the results, the reactivity of the metal species added to the ferrite mediums decreased in the order of Cu>Co>Ni>Mn, on the basis of water-splitting temperature. It was also found that the produced hydrogen amounts in the water-splitting step on partial reduced mediums were corresponding to the consumed hydrogen amounts in the previously partial reduction step.

• Proceedings of the KIEE Conference
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• 2000.07c
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• pp.1646-1648
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• 2000

This paper investigated structural and electrical properties of $Y_{2}O_3$ as a buffer layer of sin91r transistor FRAM (ferroelectric RAM). $Y_{2}O_3$ buffer layers were deposited at a low substrate temperature below 400$^{\circ}C$ and then RTA (rapid thermal anneal) treated. Investigated parameters are substrate temperature, $O_2$ partial pressure, post- annealing temperature, and suppression of interfacial $SiO_2$ layer generation. for a well-fabricated sample, we achieved that leakage current density ($J_{leak}$) in the order of $10^{-7}A/cm2$, breakdown electric field ($E_{br}$) about 2 MV/cm for $Y_{2}O_3$ film. Capacitance versus voltage analysis illustrated dielectric constants of 7.47. We successfully achieved an interface state density of $Y_{2}O_3$/Si as low as $8.72{\times}10^{10}cm^{-2}eV^{-1}$. The low interface states were obtained from very low lattice mismatch less than 1.75%.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.07a
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• pp.47-50
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• 2000

This paper investigated structural and electrical properties of $Y_2$ $O_3$ as a buffer layer of single transistor FRAM (ferroelectric RAM). $Y_2$ $O_3$ buffer layers were deposited at a low substrate temperature below 40$0^{\circ}C$ and then RTA (rapid thermal anneal) treated. Investigated parameters are substrate temperature, $O_2$ partial pressure, post-annealing temperature, and suppression of interfacial $SiO_2$ layer generation. For a well-fabricated sample, we achieved that leakage current density ( $J_{leak}$) in the order of 10$^{-7}$ A/$\textrm{cm}^2$, breakdown electric field ( $E_{br}$ ) about 2 MV/cm for $Y_2$ $O_3$ film. Capacitance versus voltage analysis illustrated dielectric constants of 7.47. We successfully achieved an interface state density of $Y_2$ $O_3$/Si as low as 8.72x1010 c $m^{-2}$ e $V^{-1}$ . The low interface states were obtained from very low lattice mismatch less than 1.75%.

• Progress in Superconductivity
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• v.7 no.1
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• pp.52-57
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• 2005

[ $YBa_{2}Cu_{3}O_y$ ] superconducting films were prepared on $LaAlO_3$(100) single crystal substrate by spray pyrolysis method. The precursor solution was prepared by dissolving nitrate powders in de-ionized water. Both of ultrasonic and concentric nebulizers were used in order to generate fine droplets of precursor solution. C-axis oriented films were obtained at deposition temperature of $750\~850^{\circ}C$ and working pressure of 100 Torr and 500 Torr. In case of ultrasonic nebulizer, films showed rough and porous surface morphology due to formation of enormous droplets, while smooth and dense films were obtained for concentric nebulizer. A transport $J_c$ value of $0.43\;MA/cm^2$ at 77 K and self field was achieved on $LaAlO_3$(100) single crystal substrate.

• Journal of Magnetics
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• v.1 no.1
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• pp.46-50
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• 1996

Highly oriented ${BaFe_{12}{O_{19}$ films were obtained by a KrF excimer laser ablation technique using (110)$(012){Al_2}{O_3}$(001)$(012){Al_2}{O_3}$ and $(012){Al_2}{O_3}$ substrates, respectively.The degree of alignment of more than 95% were achieved for (100) on (110)$(012){Al_2}{O_3}$ and (001)$(001){Al_2}{O_3}$ planes, and heteroepitaxial films of (114) on (012)$(012){Al_2}{O_3}$were possible to be grown with a lasing energy density of 6.67 J/$cm^2$ at an oxygen partial pressure ${PO_2}$ of 900 mTorr. The best magnetic properties were obtained from the as-deposited films at the substrate temperature of $700^{\circ}C$, and post annealing treatment was not needed to enhance the magnetic properties. Experimentally saturated magnetization ($4_pi M_S$) of 3600~3800 Gauss and coercivities $(H_c)$ of 3050~3080 Oe, which approach 85% of those of Ba-ferrite bulk composed of single domain particles, were obtained in this study.