• 한국전기화학회:학술대회논문집
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• 2001.06a
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• pp.33-36
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• 2001

• Journal of the Korean Magnetics Society
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• v.27 no.4
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• pp.123-128
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• 2017

The magnetic isotropy property from the magnetoresistance (MR) curve and magnetization (MH) loop for the PtMn based spin valve (SV) multilayer films fabricated with different the bottom structure after post-annealing treatment was investigated. The exchange biased coupling field ($H_{ex}$), coercivity ($H_c$), and MR ratio of Glass/Ta(10 nm)/CoFe(6 nm)/Cu(2.5 nm)/CoFe(3 nm)/Ta(4 nm) SV multilayer film without antiferromagnetic PtMn layer are 0 Oe, 25 Oe, and 3.3 %, respectively. MR curve for the Glass/Ta(10 nm)/CoFe(6 nm)/Cu(2.5 nm)/CoFe(3 nm)/PtMn(6 nm)/Ta(4 nm) SV multilayer film showed $H_{ex}=2Oe$, $H_c=316Oe$, and MR (%) = 4.4 % with one butterfly MR curve having by the effect of antiferromagnetic PtMn layer. MR curve for the dualtype Glass/Ta(10 nm)/CoFe(6 nm)/Cu(2.5 nm)/CoFe(3 nm)/PtMn(6 nm)/CoFe(3 nm)/Cu(2.5 nm)/CoFe(6 nm)/Ta(4 nm) SV multilayer film showed $H_c=37.5Oe$ and 386 Oe, MR = 3.5 % and 6.5 % with two butterfly MR curves and square-like hysteresis MH loops. The anisotropy property in CoFe spin valve-PtMn multilayer is neglected by the effects of a very small value of $H_{ex}$ and a very slightly shape magnetic anisotropy. This result is possible to explain the effect of magnetization configuration spin array of the bottom SV film and the top SV film of PtMn layer.

• Bulletin of the Korean Chemical Society
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• v.31 no.7
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• pp.1968-1972
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• 2010

Pt-Co alloy nanowire array was directly synthesized by electrochemical deposition with polycarbonate template at -1.0V and subsequent chemical etching of the template. The use of Pt-Co alloy nanowire array-modified electrode (Pt-Co NAE) for the determination of morphine (MO) is described. The morphology of the Pt-Co alloy nanowire array has been investigated by scanning electron microscopy (SEM) and energy disperse X-ray spectroscopy (EDS) analysis), respectively. The resulting Pt-Co NAE offered a linear amperometric response for morphine ranging from $2.35\times10^{-5}$ to $2.39\times10^{-3}$ M with a detection limit of $7.83\times10^{-6}$ M at optimum conditions. This sensor displayed high sensitivity and long-term stability.

• Proceedings of the KIEE Conference
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• 1998.07d
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• pp.1349-1351
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• 1998

Platinum-Cobalt alloy thin films were deposited on $Al_2O_3$ substrates by r.f. cosputtering for RTD temperature sensors. We made Pt-Co alloy resistance patterns on the $Al_2O_3$ substrates by lift-off method and investigated the physical and electrical characteristics of these films under various conditions (the input power, working vacuum, annealing temperature, thickness of thin films) and also after annealing these films. At input power of Pt : $4.4 W/cm^2$. Co:6.91W/$cm^2$. working vacuum of 10 mTorr and annealing conditions of $1000^{\circ}C$ and 60 min, the resistivity and sheet resistivity of Pt-Co thin films was $15{\mu}{\Omega}{\cdot}cm$ and $0.5{\Omega}/{\square}$, respectively. The TCR value of Pt-Co alloy thin films was measured with various thickness of thin films and annealing conditions. The optimum TCR value is gained under conditions $3000{\AA}$ of thin films thickness and $1000^{\circ}C$ of annealing temperature. These results indicate that Pt-Co alloy thin films have potentiality for the high resolution RTD temperature sensors.

• Bulletin of the Korean Chemical Society
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• v.33 no.6
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• pp.1993-1997
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• 2012

Mg-doped ZnO one-dimensional (1D) nanostrutures were synthesized by using a thermal evaporation technique. The morphology, crystal structure, and sensing properties of the Mg-doped ZnO nanostructures functionalized with Pt to CO gas at $100^{\circ}C$ were examined. The diameters of the 1D nanostructures ranged from 80 to 120 nm and that the lengths were up to a few tens of micrometers. The gas sensors fabricated from multiple networked Mg-doped ZnO nanowires functionalized with Pt showed enhanced electrical response to CO gas. The responses of the nanowires were improved by approximately 70, 69, 111, and 81 times at CO concentrations of 10, 25, 50, and 100 ppm, respectively. Both the response and recovery times of the nanowire sensor for CO gas sensing were not nearly changed by Pt functionalization. It also appeared that the Mg doping concentration did not influence the sensing properties of ZnO nanowires as strongly as Pt-functionalization. In addition, the mechanism for the enhancement in the CO gas sensing properties of Mg-doped ZnO nanowires by Pt functionalization is discussed.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.02a
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• pp.246-246
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• 2012

Smart catalyst design though novel catalyst preparation methods can improve catalytic activity of transition metals on reducible oxide supports such as titania by enhancement of metal oxide interface effects. In this work, we investigated Pt nanoparticles/titania catalysts under CO oxidation reaction by using novel preparation methods in order to enhance its catalytic activity by optimizing metal oxide interface. Arc plasma deposition (APD) and metal impregnation techniques are employed to achieve Pt metal deposition on titania supports which are prepared by multi-target sputtering and Sol-gel techniques. In order to tailor metal-support interface for catalytic CO oxidation reaction, Pt nanoparticles and thin films are deposited in varying surface coverages on sputtered titania films using APD. To assess the role of oxide support at the interface, APD-Pt is deposited on sputtered and Sol-gel prepared titania films. Lastly, characteristics of APD-Pt process are compared with Pt impregnation technique. Our results show that activity of Pt nanoparticles is improved when supported over Sol-Gel prepared titania than sputtered titania film. It is suggested that this enhanced activity can be partly ascribed to a very rough titania surface with the higher free metal surface area and higher number of sites at the interface between the metal and the support. Also, APD-Pt shows superior catalytic activity under CO oxidation as compared to Pt impregnation on sputtered titania support. XPS results show that bulk oxide is formed on Pt when deposited through impregnation and has higher proportion of oxidized Pt in the form of $Pt^{2+/4+}$ oxidation states than Pt metal. APD-Pt shows, however, mild oxidation with large proportion of active Pt metal. APD-Pt also shows trend of increasing CO oxidation activity with number of shots. The activity continues to increase with surface coverage beyond 100%, thus suggesting a very rough and porous Pt films with higher active surface metal sites due to an increased surface area available for the reactant CO and $O_2$ molecules. The results suggest a novel approach for systematic investigation into metal oxide interface by rational catalysts design which can be extended to other metal-support systems in the future.

• Journal of Magnetics
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• v.9 no.4
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• pp.121-124
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• 2004

NiO thickness dependences of perpendicular magnetic anisotropy (PMA) in the $NiO/[CoFe/Pt]_5$ multilayers for exchange biasing and $[CoFe/Pt]_4/Pt/[CoFe/Pt]_4$ for interlayer exchange coupling were investigated. Perpendicular magnetization curve was obtained by out-of-plane extraordinary Hall measurement. Magnetic force microscopy (MFM) has been used for the investigation of magnetic domains on thin films. We confirmed that the interlayer exchange coupling (IEC) as a function of NiO thickness at room temperature existed with a period of two monolayers.

• Applied Chemistry for Engineering
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• v.29 no.6
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• pp.657-662
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• 2018

In this study, the effect of $Pt/TiO_2$ catalysts on the CO oxidation reaction at room temperature was investigated using various $TiO_2$ supports with different physical properties to compare and evaluate $Pt/TiO_2$ catalysts. Physicochemical properties of the catalyst were alanyzed using XPS, CO-chemisorption, BET, and CO-TPD. As a result, when the active particle diameter was smaller, while the metal dispersion and surface area were larger, the CO room temperature oxidation reaction was better. These physical properties increased the number of active sites, causing the target material to increase the adsorption amount of CO. In addition, when the $O_2$-consumption increased, the CO-room temperature oxidation reaction activity increased due to the excellent oxygen-transferring ability.

• Journal of Magnetics
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• v.5 no.4
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• pp.143-146
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• 2000

In this study, the magnetic properties of CoCrPt films (far longditudinal recording) on a novel VMn underlayer were measured and compared with similar films on conventional Cr underlayers. It was found that the VMn film had (200) preferred orientation and the lattice constant was about 0.2967 nm, which is slightly larger than that of the Cr film, 0.2888 m. The grain size of the VMn film was 9.8 nm at 30 m thickness, about 39% smaller than that of a similarly deposited Cr. The CoCrPt/VMn films showed higher coercivity in comparison with the CoCrPt/Cr films. The coercivity increase is attributed to the increased Co (11.0) texture, improved lattice matching between Co (11.0) and VMn (200), and lower stacking fault density. V or Mn must have diffused into the CoCrPt magnetic layer uniformly rather than preferentially along grain boundaries. This reduced Ms at higher substrate temperature.

• Transactions of the Korean hydrogen and new energy society
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• v.23 no.6
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• pp.581-587
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• 2012

Thermal aging effect on NSR kinetics was studied over Pt/Co/Fe/Ba/$Al_2O_3$ catalyst. The amount of $NO_x$ uptake over Pt/Co/Fe/Ba/$Al_2O_3$ calcined at $400^{\circ}C$ increased with increasing NSR temperature from $200^{\circ}C$ to $400^{\circ}C$, where amount of $NO_x$ uptake is the highest at $400^{\circ}C$ with mol ratio of $NO_x$/Ba = 0.5. Thereafter, the amount of $NO_x$ uptake at $400^{\circ}C$ decreased with the higher calcination temperature, where Pt/Co/Fe/Ba/$Al_2O_3$ catalyst calcined at $700^{\circ}C$ showed an amount of $NO_x$ uptake with the mol ratio of $NO_x$/Ba=0.062. Result of XRD and NSR showed that Fe addition into Pt/Co/Fe/Ba/$Al_2O_3$ suppressed sintering of Pt crystallites and make $NO_x$ uptake larger, compared to no addition of Fe into Pt/Co/Fe/Ba/$Al_2O_3$ catalyst. From BET result, it was found that the change of specific surface area was relatively small by the thermal aging process. Therefore, it was found that the sintering of Pt crystallites caused the decrease of $NO_x$ uptake during NSR reaction and Fe played a role to suppress the sintering process of Pt crystallites caused by thermal aging.