• 한국세라믹학회지
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• 제54권2호
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• pp.137-140
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• 2017

A $TiO_2$ nanofilm was deposited on ${\alpha}-Fe_2O_3$ nanopowders using the atomic layer deposition method. The $TiO_2$ film was prepared at $300^{\circ}C$ using $Ti(N(CH_3)_2)_4$ and $H_2O$ as the precursor and reactant gas, respectively. The thickness and composition of the $TiO_2$ surface were characterized by TEM and EDS measurements. The TEM results showed that the growth rate of the film was about $0.12{\AA}/cycle$. The EDS and SAED analyses showed the presence of titanium oxide on the surface of the ${\alpha}-Fe_2O_3$ nanopowders, confirming the deposition of the $TiO_2$ nanofilm. The Zeta potential and sedimentation test results showed that the dispersibility of the coated nanopowders was higher than that of the uncoated nanopowders. This is attributed to the electrostatic repulsion between the $TiO_2$-coated layers on the surface of the ${\alpha}-Fe_2O_3$ nanopowders. The results revealed that the $TiO_2$-coated layers modified the surface characteristics of the ${\alpha}-Fe_2O_3$ nanopowders and improved their dispersibility.

• 한국재료학회지
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• 제12권6호
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• pp.482-487
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• 2002

A $TiO_2$ film for photocatalyst was prepared by anodic oxidation at 180V in acidic electrolyte and film formation mechanism was studied. The major part of anodic $TiO_2$ film consisted of anatase type structure and surface morphology exhibited a porous cell structure. The thickness growth rate of the oxide film with anodization time revealed two-stage slope corresponds to the surface morphology between anodic films. The growth of pores on cell structure and the growth rate of film with two-stage slope are related to the constant formation rate of the $TiO_2$ layer.

• 한국분말야금학회:학술대회논문집
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• 한국분말야금학회 2006년도 Extended Abstracts of 2006 POWDER METALLURGY World Congress Part2
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• pp.1110-1111
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• 2006

[ $Ti_3SiC_2$ ] was coated with $Al_2O_3$, MgO and $SiO_2$ respectively by sol-gel method and cured at 900 and $1200^{\circ}C$. The coated oxides did not react with $Ti_3SiC_2$ at $900^{\circ}C$ but reacted with it to form $TiC_x$ at $1200^{\circ}C$. The specimen coated with $SiO_2$ at $900^{\circ}C$ formed a dense protecting layer and showed the best oxidation resistance at $800^{\circ}C$ in air. However, the dense protecting layers did not form in $Al_2O_3$ and MgO coated specimens cured even at $900^{\circ}C$. MgO coated specimen showed the worst improvement in the oxidation resistance because the reactivity of MgO with $Ti_3SiC_2$ was highest. On the other hand, the electrical conductivities were measured in MgO and $Al_2O_3$ coated specimens to have TiCx but could not be measured in the $SiO_2$ coated ones because of the nonconductive dense protected layers.

• 한국전기전자재료학회논문지
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• 제11권6호
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• pp.436-441
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• 1998

$Pt/SrTiO_3/Pb_x(Zr_{0.52}, Ti_{0.48})O_3/SrTiO_3/Si$ structure was prepared by rf-magnetron sputtering method for use in nondestructive read out ferroelectric RAM(NDRO-FEAM). PBx(Zr_{0.52}Ti_{0.48})O_3}$(PZT) and $SrTiO_3$(STO) films were deposited respectively at the temperatures of $300^{\circ}C and 500^{\circ}C$on p-Si(100) substrate. The role of the STO film as a buffer layer between the PZT film and the Si substrate was studied using X-ray diffraction (XRD), Auger electron spectroscopy (ASE), and scanning electron microscope(SEM). Structural analysis on the interfaces was carried out using a cross sectional transmission electron microscope(TEM). For PZT/Si structure, mostly Pb deficient pyrochlore phase was formed due to the serious diffusion of Pb into the Si substrate. On the other hand, for STO/PZT/STO/Si structure, the PZT film had perovskite phase and larger grain size with a little Pb interdiffusion. the interfaces of the PZT and the STO film, of the STO film and the interface layer and $SiO_2$, and of the $SiO_2$ and the Si substate had a good flatness. Across sectional TEM image showed the existence of an amorphous layer and $SiO_2$ with 7nm thickness between the STO film and the Si substrate. The electrical properties of MIFIS structure was characterized by C-V and I-V measurements. By 1MHz C-V characteristics Pt/STO(25nm)/PZT(160nm)/STO(25nm)/Si structure, memory window was about 1.2 V for and applied voltage of 5 V. Memory window increased by increasing the applied voltage and maximum voltage of memory window was 2 V for V applied. Memory window decreased by decreasing PZT film thickness to 110nm. Typical leakage current was abour $10{-8}$ A/cm for an applied voltage of 5 V.

• 한국안광학회지
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• 제5권1호
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• pp.7-11
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• 2000

ITO, $TiN_xW_y$, Ag 등의 전도성 흡수층으로 무반사, 무정전 광학박막을 Essential Macleod 프로그램을 이용하여 설계했다. 그 결과 [공기 ${\mid}SiO_2{\mid}TiN_xW{\mid}$ 유리] 층은 단 두층코팅막으로 가시광선 파장영역(45~700nm)에서 넓게 무반사 코팅이 되었다. 이 때 반사률과 투과률은 각각 0.5% 미만과 약 75%이다. [공기 $SiO_2{\mid}TiO_2{\mid}SiO_2{\mid}ITO {\mid}$ 유리] 층은 약 0.5% 미만의 반사률이 있는 무반사 코팅이 되며 투과률은 97% 이상이며, 450nm 파장 영역부근에서 투과률이 비교적 낮은 것은 ITO의 흡수계수 영향 때문이다. 또한 [공기 $SiO_2{\mid}TiO_2{\mid}SiO_2{\mid}Ag{\mid}$ 유리] 층은 반사률이 1~2%인 AR코팅이며 투과률은 96% 이상이다.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2011년도 제41회 하계 정기 학술대회 초록집
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• pp.109-109
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• 2011

CO oxidaition reacitvity of bare and $TiO_2$ -coated NiO/$Ni(OH)_2$ nanoparticles was studied. For the deposition of $TiO_2$ atomic layer deposition was used, and formation of three-dimensional island of $TiO_2$ on NiO/$Ni(OH)_2$ could be identified. Based on the data of X-ray Photoelectron Spectroscopy, we suggest that only $Ni(OH)_2$ existed on the surface, whereas NiO disappeared upon $TiO_2$ deposition. Both CO adsorption and CO oxidation took place on NiO/$Ni(OH)_2$ surfaces under our experimental conditions. CO adsorption was completely suppressed after $TiO_2$ deposition, whereas CO oxidation activity was maintained to large extent. It is proposed that bare NiO can uptake CO under our experimental condition, whereas hydroxylated surface of NiO can be active for CO oxidation.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2008년도 추계학술대회 논문집 Vol.21
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• pp.444-444
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• 2008

For the polymer tandem cell, simple and advantaged solution-based method to electron transport intermediate layer is presented which are composed $TiO_2$ nanoparticles. Device were based on a regioregular Poly(3-hexylthiophene)(P3HT) and [6,6]-phenyl $C_{61}$ butyric acid methyl ester($PC_{60}BM$) blend as a donor and acceptor bulk-heterojunction. For the middle electrode interlayer, the $TiO_2$ nanoparticles were well dispersed in ethanol solution and formed thin layer on the P3HT:PCBM charge separation layer by spin coating. The layer serves as the electron transport layer and divides the polymer tandem solar cell. The open-circuit voltage (Voc) for the polymer tandem solar cells was closed to the sum of those of individual cells.

• 한국재료학회지
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• 제31권10호
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• pp.552-561
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• 2021

For the purpose of manufacturing a high efficiency TiO₂ photocatalyst, B-doped TiO₂ photocatalysts are synthesized using a plasma electrolytic oxidation method in 0.5 M H₂SO₄ electrolyte with different concentrations of H₃BO₃ as additive. For the B doped TiO₂ layer fabricated from sulfuric electrolyte having a higher concentration of H₃BO₃ additive, the main XRD peaks of (101) and (200) anatase phase shift gradually toward the lower angle direction, indicating volume expansion of the TiO₂ anatase lattice by incorporation of boron, when compared with TiO₂ layers formed in sulfuric acid with lower concentration of additive. Moreover, XPS results indicate that the center of the binding energy peak of B1s increases from 191.45 eV to 191.98 eV, which suggests that most of boron atoms are doped interstitially in the TiO₂ layer rather than substitutionally. The B doped TiO₂ catalyst fabricated in sulfuric electrolyte with 1.0 M H₃BO₃ exhibits enhanced photocurrent response, and high efficiency and rate constant for dye degradation, which is ascribed to the synergistic effect of the new impurity energy band induced by introducing boron to the interstitial site and the improvement of charge transfer reaction.

• 한국표면공학회지
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• 제29권6호
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• pp.839-846
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• 1996

Epitaxial (La, Sr)$CoO_3/Pb(Zr,\;Ti)O_3/(La,\;Sr)CoO_3$by pulsed laser deposition for ferroelectric field effect transistor. Epitaxial $LaCoO_3/Pb(Zr,\;Ti)O_3/(La,\;Sr)CoO_3$ heterostructures exhibited 70$\mu C/cm^2$ and 17 $\mu C/cm^2$at a positively and negatively poled states, respectively. On the other hand, epitaxial (La, Sr)$CoO_3/Pb(Zr,\;Ti)O_3/LaCoO_3$heterostructures show the remnant polarization states opposite to the $LaCoO_3/Pb(Zr,\;Ti)O_3/(La,\;Sr)CoO_3$ heterostructures. This indicates that the interface between (La, Sr)$CoO_3$ (LSCO) and $Pb(Zr, Ti)O_3(PZT)$ layers affects the asymmetric polarization remanence through electrochemical nature. The resistivity of $LaCoO_3$ (LCO) layer was found to be dependent on an ambient oxygen, primarily the ambient oxygen pressure during deposition. The resistivity of the LCO layer varied in the range of 0.1-100 $\Omega$cm. It is suggested that, with an appropriate resistivity of the LCO layer, the LCO/PZT/LSCO heterostructure can be used as the ferroelectric field effect transistor.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2013년도 제45회 하계 정기학술대회 초록집
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• pp.75.2-75.2
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• 2013

Atomic layer deposition (ALD), utilizing self-limiting surface reactions, could offer promising perspectives for future efficient energy conversion devices. The capabilities of ALD for surface/interface modification and construction of novel architectures with sub-nanometer precision and exceptional conformality over high aspect ratio make it more valuable than any other deposition methods in nanoscale science and technology. In the context, a variety of researches on fabrication of active materials for energy conversion applications by ALD are emerging. Among those materials, one-dimensional nanotubular titanium dioxide, providing not only high specific surface area but also efficient carrier transport pathway, is a class of the most intensively explored materials for energy conversion systems, such as photovoltaic cells and photo/electrochemical devices. The monodisperse, stoichiometric, anatase, TiO2 nanotubes with smooth surface morphology and controlled wall thickness were fabricated via low-temperature template-directed ALD followed by subsequent annealing. The ALD-grown, anatase, TiO2 nanotubes in alumina template show unusual crystal growth behavior which allows to form remarkably large grains along axial direction over certain wall thickness. We also fabricated dye-sensitized solar cells (DSCs) introducing our anatase TiO2 nanotubes as photoanodes, and studied the effect of blocking layer, TiO2 thin films formed by ALD, on overall device efficiency. The photon convertsion efficiency ~7% were measured for our TiO2 nanotubebased DSCs with blocking layers, which is ~1% higher than ones without blocking layer. We also performed open circuit voltage decay measurement to estimate recombination rate in our cells, which is 3 times longer than conventional nanoparticulate photoanodes. The high efficiency of our ALD-grown, anatase, TiO2 nanotube-based DSCs may be attributed to both enhanced charge transport property of our TiO2 nanotubes photoanode and the suppression of recombination at the interface between transparent conducting electrode and iodine electrolytes by blocking layer.