• Bulletin of the Korean Chemical Society
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• v.34 no.7
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• pp.2056-2062
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• 2013

The dihydroxy naphthalene/$TiO_2$ complexes with different substitution patterns were prepared by surface modification. X-ray diffraction, UV-Vis spectroscopy, photoluminescence, and X-ray photoelectron spectroscopy were used to characterize the prepared composite materials. The results indicated that the surface modification did not influence the crystallization of $TiO_2$. The visible-light absorbances of prepared dihydroxy naphthalene/$TiO_2$ complexes could be assigned to the ligand-to-metal charge transfer. The obtained catalyst exhibited outstanding photocatalytic activity and stability under visible light. A linear relationship existed between the percentages of hydroxynaphthalenes coordinated on $TiO_2$ surface and $H_2$ production ability. The substitution pattern of dihydroxy naphthalene and $CH_3OH$ content could also influence the photocatalytic performance remarkably. The photocatalytic $H_2$ production ability was further improved after loading with ultra low concentration of Pt, 0.02 wt %. The possible mechanism was proposed.

• Korean Journal of Crystallography
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• v.11 no.2
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• pp.95-101
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• 2000

Ferroelectric SrBi2Ta2O9 (SBT) thin films of Pt/Ti/SiO2 electrode were fabricated using a sintered SBT target with various Bi2O3 content by rf magnetron sputtering. Good hysteresis loop characteristics were observed in the SBT thin films deposited with 50mol% excess Bi target. SBT thin films crystallized from 650℃ however, good hysteresis loop can be obtained in the film annealed above 700℃. pt/TiO2/SiO2 and Pt/SiO2 electrodes were also used to investigate the Pt electrode dependence of SBT thin films. SBT thin films showed random oriented polycrystalline structure and similar morphology regardless of electrodes with quite different surface morphology. A 0.2㎛ thick SBT film annealed at 750℃ exhibited the remanent polarization (2Pr) of μC/㎠ and coercive voltage(Vc) of 1V at an applied voltage of 5V.

• Analytical Science and Technology
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• v.18 no.2
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• pp.120-129
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• 2005

Volatile organic compounds (VOCs) have been recognized as major contributor to air pollution. The catalytic oxidationis is one of the most important processes for VOCs destruction due to the possibility getting high efficiency at low temperature. In this study, monometallic Pt, Ir and bimetallic Pt-Ir were supported to $TiO_2$. In order to distribute metals uniformly, $H_2O-H_2$ treatment method was used. Xylene, toluene and MEK were used as reactants. The monometallic or bimetallic catalysts were prepared by the excess wetness impregnation method and characterized by XRD, XPS, and TEM analysis. Pt catalyst showed higher conversion than Ir catalyst and Pt-Ir bimetallic catalyst showed the highest conversion. The catalysts prepared by $H_2O-H_2$ treatment had better VOC's conversion than that of nothing treatment. In the VOCs oxidation, Pt-Ir bimetallic catalysts had multipoint active sites, so it improved the range of Pt metal state. Therefore, bimetallic catalysts showed higher conversion of VOCs than monometallic ones. $H_2O-H_2$ treatment effected an uniform distribution of Pt particles. In VOCs oxidation was found to follow first order reaetion kinetics. The activation energy of $H_2O-H_2$ treatment catalysts was lower than that of untreated ones. In this study, the a small amount of Ir was used with Pt to promote the oxidation conversion of VOCs.

• Proceedings of the Korean Society Of Semiconductor Equipment Technology
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• 2006.10a
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• pp.170-173
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• 2006

Ferroelectric $Bi_{3.35}Sm_{0.65}Ti_3O_{12}(BST)$ thin films were deposited on $Pt(111)/Ti/SiO_2/Si(100)$ substrates by a sol-gel spin-coating process. In this experiments, $Bi(TMHD)_3$, $Sm_5(O^iPr)_{13}$, $Ti(O^iPr)_4$ were used as precursors, which were dissolved in 2-methoxyethanol. Thereafter, the thin films with the thickness, of 240nm were annealed from 600 to $720^{\circ}C$ in oxygen atmosphere for 1 hr, and post-annealed in oxygen atmosphere for 1 hr after deposition of Pt electrode to enhance the electrical properties. The remanent polarization and coercive voltage of the BST thin films annealed at $720^{\circ}C$ were $19.48\;{\mu}C/cm^2$ and 3.40 V, respectively, and a fatigue-free characteristics. As a result, Sm-substituted bismuth titanate films with good ferroelectric properties and excellent fatigue resistance are useful candidates for ferroelectric memory applications.

• Proceedings of the KIEE Conference
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• 2001.11a
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• pp.9-11
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• 2001

차세대 고속 DRAM기술에 사용될 금속인 Cu의 확산 방지막(diffusion harrier) 물질로는 Ta 또는 W 같은 Refractory metal 이 융점(melting point)이 높고 저항값이 낮아 많이 연구 보고되고 있으나, 본 논문에서는 초고주파 소자에서 Au의 확산 방지 막으로 많이 사용되고 있으며. 선택적 증착이 용이한 Pt과 Ni를 MOS 소자의 Cu 확산 방지 막으로 적용하며 어닐링한 후 소자의 게이트 산화막 누설전류($I_{leak}$), 그리고. Si/$SiO_2$ 계면의 trap density 등의 변이를 측정하여 Cu가 소자의 특성 열화에 미치는 영향을 연구하였다. 실험 결과 Pt/Ti($200{\AA}/100{\AA}$)를 적용한 경우 소자 측성 열화가 가장 적었으며. 이는 Copper의 확산 방지막으로 Pt/Ti를 사용하여 전기적 특성 및 계면 특성을 개선시킬 수 있음을 보여 주었다. 이는 SIMS Profile을 통해서도 확인하였다.

• Proceedings of the Materials Research Society of Korea Conference
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• 2007.11a
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• pp.66.2-66.2
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• 2007

• Korean Journal of Materials Research
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• v.22 no.7
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• pp.342-345
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• 2012

The dielectric properties and phase transformation of poled <001>-oriented $Pb(Mg_{1/3}Nb_{2/3})O_3-x%PbTiO_3$(PMN-x%PT) single crystals with compositions of x = 20, 30, and 35 mole% are investigated for orientations both parallel and perpendicular to the [001] poling direction. An electric-field-induced monoclinic phase was observed for the initial poled PMN-30PT and PMN-35PT samples by means of high-resolution synchrotron x-ray diffraction. The monoclinic phase appears from $-25^{\circ}C$ to $100^{\circ}C$ and from $-25^{\circ}C$ to $80^{\circ}C$ for the PMN-30PT and PMN-35PT samples, respectively. The dielectric constant (${\varepsilon}$)-temperature (T) characteristics above the Curie temperature were found to be described by the equation$(1/{\varepsilon}-1/{\varepsilon}_m)^{1/n}=(T-T_m)/C$, where ${\varepsilon}_m$ is the maximum dielectric constant and $T_m$ is the temperature giving ${\varepsilon}_m$, and n and C are constants that change with the composition. The value of n was found to be 1.82 and 1.38 for 20PT and 35PT, respectively. The results of mesh scans and the temperature-dependence of the dielectric constant demonstrate that the initial monoclinic phase changes to a single domain tetragonal phase and a to paraelectric cubic phase. In the ferroelectric tetragonal phase with a single domain state, the dielectric constant measured perpendicular to the poling direction was dramatically higher than that measured in the parallel direction. A large dielectric constant implies easier polarization rotation away from the polar axis. This enhancement is believed to be related to dielectric softening close to the morphotropic phase boundary.

• Journal of the Korean Magnetics Society
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• v.17 no.6
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• pp.221-225
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• 2007

The effects of $Ga^+$ ion irradiation on the magnetic properties of the $Co_{73}Pt_{27}-TiO_2$ perpendicular magnetic recording media were investigated. As $Ga^+$ ion dose increased from $1\times10^{15}ions/cm^2\;to\;30\times10^{15}ions/cm^2$, the perpendicular magnetic anisotropy was degraded and no longer observed above $20\times10^{15}ions/cm^2$ dose. The deterioration of the perpendicular magnetic anisotropy and ferromagnetic properties can be attributed to the concentration profile change due to Ga+ ion implantation. The magnetic islands of $70\times70nm^2\;and\;100\times100nm^2$ size were successfully fabricated with $Ga^+$ ion irradiation.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.16 no.3
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• pp.195-201
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• 2003

The (Ba,Bi,Sr)TiO$_3$[BBST] thin films were fabricated on Pt/Ti/SiO$_2$ /Si substrate by RF sputtering method. The effects of Ar/O$_2$ ratio on the structural and dielectric properties of BBST thin films were investigated. Increasing the Ar/O$_2$ ratio, the intensity of BaBi$_4$Ti$_4$O$_{15}$ and Bi$_4$Ti$_3$O$_{12}$ peaks were increased but (Ba$_{0.5}$Sr$_{0.5}$)TiO$_3$ peak was decreased. In the BBST thin films deposited with condition of Ar/O$_2$(90/10) ratio, the composition ratio of the Ba, Bi and Sr atoms were 0.35, 0.25 and 0.4 respectively. The Bi and Ti atoms were diffused into the Pt layers. Increasing the Ar/O$_2$ ratio, the dielectric constant of the BBST thin films were increased but the dielectric loss of the BBST thin films were decreased. The dielectric constant and dielectric loss of the BBST deposited at 90/10 of Ar/O$_2$ ratio were 319 and 2.2%. respectively . Increasing the applied voltage, the capacitance of the BBST thin films were decreased.reased.

• Journal of the Korean Solar Energy Society
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• v.23 no.4
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• pp.29-35
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• 2003

We studied the water splitting into $H_2$ and $O_2$ using two different semiconductor photo catalysts and redox mediator, mimicking the Z-scheme mechanism of the photosynthesis, $H_2$ evolution took place on a Pt-$SrTiO_2$ (Cr-Ta doped) photocatalyst using $I^-$ electron donor under the visible light irradiation. The Pt-$WO_3$ photocatalyst showed an excellent activity of the $O_2$ evolution using $IO_3^-$ electron acceptor under visible light. $H_2$ and $O_2$ gases evolved in the stoichiometric ratio($H_2/O_2$=2) under visible light using a mixture of the Pt-$WO_3$ and Pt-$SrTiO_3$ (Cr-Ta doped) suspended in NaI aqueous solution. We proposed a two-step photo-excitation mechanism using redox mediator under the visible irradiation.