• Bulletin of the Korean Chemical Society
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• 제34권7호
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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.

• 한국결정학회지
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• 제11권2호
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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.

• 분석과학
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• 제18권2호
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• pp.120-129
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• 2005

VOC는 대기오염의 주원인으로서 인식되어왔다. 촉매산화는 저온에서 높은 효율을 나타내기 때문에 VOCs 제거를 위한 가장 중요한 처리기술중 하나이다. 이 연구에서는 $TiO_2$ 담체에 Pt, Ir 그리고 Pt-Ir을 담시지켜 촉매를 제조하였다. 금속 분산에 따르면 $H_2O-H_2$ 처리방법이 사용되었고, 반응물로서 Xylene,Toluene 그리고 MEK을 사용하였다. 단일 또는 두 가지 이상의 촉매들은 함침법에 의해 준비하였고, XRD, XPS, TEM 분석을 통하여 특성화하였다. 그 결과 Pt 촉매는 Ir 촉매에 비해 더 높은 전환율을 나타내었고, Pt-Ir 촉매는 가장 높은 전환율을 나타내었다. $H_2O-H_2$ 처리한 촉매들은 처리하지 않은 것보다 VOCs 전환율이 높았다. VOCs 산화에서, Pt-Ir 촉매는 다양한 활성점을 나타내었고 그것은 Pt의 metal 영역을 강화시켰다. 따라서 두 가지 금속으로 이루어진 촉매가 단일 금속으로 이루어진 촉매에 비해 VOCs 전환율이 더 높았다. $H_2O-H_2$ 처리가 Pt 입자의 분산에서 형태에 영향을 미쳤다. 동역학적으로 VOCs 산화는 1차 반응이다. $H_2O-H_2$ 처리한 촉매들의 활성화에너지가 처리하지 않은 것들보다 낮았다. 이 연구에서 Pt에 Ir을 소량첨가함으로써 VOCs 산화반응에 효과적이었다.

• 한국반도체및디스플레이장비학회:학술대회논문집
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• 한국반도체및디스플레이장비학회 2006년도 추계학술대회 발표 논문집
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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.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2001년도 추계학술대회 논문집 전기물성,응용부문
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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.

• 한국재료학회:학술대회논문집
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• 한국재료학회 2007년도 추계학술발표대회 및
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• pp.66.2-66.2
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• 2007

• 한국재료학회지
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• 제22권7호
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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.

• 한국자기학회지
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• 제17권6호
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• pp.221-225
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• 2007

[ $Co_{73}Pt_{27}-TiO_2$ ] 수직자기 기록매체에 대해 집속이온빔(FIB)을 이용한 $Ga^+$ 이온 조사에 따른 자기적 특성의 변화를 조사하였다. $Ga^+$ 이온 도즈량을 $1\times10^{15}ions/cm^2$에서 $30\times10^{15}ions/cm^2$까지 증가시켰을 때 도즈량 $20\times10^{15}ions/cm^2$ 이상에서 수직자기이방성 및 강자성 특성이 사라지는 것이 관찰되었으며, 이는 스퍼터링 효과에 따른 수직자기 기록층의 두께 감소보다는 $Ga^+$ 이온 주입에 따른 수직자기 기록매체내의 조성 분포의 변화에 따른 것으로 보인다. $Ga^+$ 이온 조사법을 이용하며 $70\times70nm^2,\;100\times100nm^2$ 크기의 자기구조체 패턴을 형성하였다.

• 한국전기전자재료학회논문지
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• 제16권3호
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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.

• 한국태양에너지학회 논문집
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• 제23권4호
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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.