Search Results - (Author, Cooperation:B. H. Park)

2018-11-06

The American Association of Immunologists (AAI)

0022-1767

1550-6606

Medicine

2011-07-02

American Association for the Advancement of Science (AAAS)

0036-8075

1095-9203

Biology

Chemistry and Pharmacology

Computer Science

Medicine

Natural Sciences in General

Physics

2018-11-24

American Association for the Advancement of Science (AAAS)

2375-2548

Natural Sciences in General

2013-10-05

American Association for the Advancement of Science (AAAS)

0036-8075

1095-9203

Biology

Chemistry and Pharmacology

Computer Science

Medicine

Natural Sciences in General

Physics

1077-3118

AIP Digital Archive

Physics

To investigate the role of the perovskite layers on fatigue behaviors, SrBi2Ta2O9(SBT) and Bi3TiTaO9 (BTT) films were prepared by pulsed laser deposition using 15% Bi-excess bulk targets. The SBT and the BTT films grown at the similar deposition conditions showed similar growth behaviors, electrical properties, and retention characteristics. However, these films showed very different fatigue behaviors. The difference should come from the oxygen stability in the perovskite layer. Our work demonstrates that oxygen stability of the perovskite layers, as well as the self-regulating adjustment of the Bi2O2 layers, should be considered in the search for new candidate materials for nonvolatile ferroelectric memory devices. © 1999 American Institute of Physics.

Electronic Resource

1077-3118

AIP Digital Archive

Physics

X-ray photoemission spectroscopy measurements were executed to compare the nature of defects in SrBi2Ta2O9 (SBT) and Bi4Ti3O12 (BTO) films. In the SBT film, it was found that the oxygen ions at the metal–oxygen octahedra were much more stable than those at the Bi2O2 layers. On the other hand, for the BTO film, oxygen vacancies could be induced both at the titanium–oxygen octahedra and at the Bi2O2 layers. We suggested that the difference in stability of the metal–oxygen octahedra should be related to different fatigue behaviors of the SBT and the BTO films. © 1999 American Institute of Physics.

Electronic Resource

1077-3118

AIP Digital Archive

Physics

Using La0.5Sr0.5CoO3 (LSCO) or Pt film as a bottom electrode layer, epitaxial Bi4Ti3O12 (BTO) thin films were grown on MgO(001) substrates by pulsed laser deposition. A symmetric Pt/BTO/Pt capacitor structure shows a surprisingly large asymmetric polarization switching behavior, but a Pt/BTO/LSCO structure has a nearly symmetric P–V hysteresis. The strong asymmetric behavior in the Pt/BTO/Pt was attributed to positive charges resulting from interdiffusion at the bottom BTO/Pt interface. P–V hysteresis studies using numerous top electrode materials and Auger electron spectroscopy depth profile measurement also support formation of interfacial charges. Imprint pulse test shows that such an imprint failure cannot be recovered by applying a dc bias field.© 1997 American Institute of Physics.

Electronic Resource

1077-3118

AIP Digital Archive

Physics

Two kinds of epitaxial Sr–Bi–Ta oxides were grown on La0.5Sr0.5CoO3(001)/LaAlO3(001) substrates by pulsed laser deposition. At a temperature higher than 650 °C, c-axis oriented SrBi2Ta2O9 films could be deposited epitaxially. At 550 °C, an epitaxial film with a cubic fluorite-like phase could be grown. Although the film with the cubic phase does not show ferroelectric properties, it has good electrical properties which are suitable for high capacitance applications. © 1998 American Institute of Physics.

Electronic Resource

1077-3118

AIP Digital Archive

Physics

A torus knot model is presented to analyze the chiral wave propagation of photonic quantum-ring lasers in a three-dimensional Rayleigh–Fabry–Perot toroidal cavity. The Rayleigh–Fabry–Perot cavity gives rise to peculiar multichromatic spectra with nonequal intermode spacings. In particular, the knot model analysis suggests a strange three-dimensional effective index ellipsoid for the cavity with a large birefringence of neff3D(z)−neff2D(x,y)(approximate)0.4–0.5. © 2002 American Institute of Physics.

Electronic Resource

1077-3118

AIP Digital Archive

Physics

We have heteroepitaxially deposited Ba0.6Sr0.4TiO3 (BST) thin films on (001)-oriented MgO substrates using pulsed-laser deposition. By optimizing the deposition temperature and adjusting the film thickness, we have successfully increased the dielectric nonlinearity and decreased the dielectric loss of BST films. BST thin films grown at 750 °C with a thickness of 1.1 μm showed a dielectric constant tunability of greater than 65% and a tunability/loss of 43 at a surface electric field of 80 kV/cm at room temperature. X-ray diffraction and transmission electron microscopy analyses indicated that the tunability and dielectric loss were closely related to the crystallinity of the BST films. © 2000 American Institute of Physics.

Electronic Resource

1077-3118

AIP Digital Archive

Physics

Polycrystalline SrBi2Ta2O9 ferroelectric thin films were grown on Pt/Ti/SiO2/Si substrates using pulsed-laser deposition. By adjusting the laser fluence, we could successfully control remnant polarization of the films. In a narrow fluence range of 1.0–1.5 J/cm2, films with large remnant polarizations (as high as 18.7 μC/cm2) could be obtained. The choice of an optimal laser fluence was found to be very important to control electrical properties of the films. From electron-probe microanalysis, it was demonstrated that the Bi content is closely related with the remnant polarization. © 1999 American Institute of Physics.

Electronic Resource

1077-3118

AIP Digital Archive

Physics

Dielectric Ba0.6Sr0.4TiO3 films doped with different weight percentages of TiO2 were deposited by pulsed-laser deposition. The dielectric constant, dielectric loss, and the dielectric tunability of the films were found to be a strong function of the weight ratio of TiO2/Ba0.6Sr0.4TiO3. Compared to the pure Ba0.6Sr0.4TiO3, the TiO2-doped Ba0.6Sr0.4TiO3 exhibits lower dielectric loss while maintaining a significantly adjustable dielectric constant and desirable capacitance tunability. The change of the dielectric properties of TiO2-doped Ba0.6Sr0.4TiO3 films is closely related to the change in microstructure of the films as revealed by transmission electron microscopy. © 2002 American Institute of Physics.

Electronic Resource

1077-3118

AIP Digital Archive

Physics

Epitaxial rutile-TiO2 and anatase-TiO2 films were grown at 800 °C on Al2O3(1¯102¯) and LaAlO3(001), respectively, using pulsed laser deposition. Both films showed high crystalline quality, evidenced by x-ray diffraction and high-resolution electron microscopy. The formation of different phases on different substrates could be qualitatively explained by the atomic arrangements at the interfaces. We also deposited epitaxial rutile-TiO2 and anatase-TiO2 films on conductive RuO2 and La0.5Sr0.5CoO3 electrodes, respectively. Using a Kelvin probe, we measured the photovoltaic properties of these multilayer structures. A rutile-TiO2 film grown on RuO2 showed a very broad peak in the visible light region. An epitaxial anatase-TiO2 film grown on La0.5Sr0.5CoO3 showed a strong peak with a threshold energy of 3.05 eV. © 2002 American Institute of Physics.

Electronic Resource

1077-3118

AIP Digital Archive

Physics

We present the wave propagation characteristics of photonic quantum ring lasers with clear evidence of the evanescence-propagation crossover behavior. The data obtained from the fiber probe measurements of 15–36 μm disk size lasers show that the Rayleigh's whispering gallery modes always give rise to the propagation mode, with the crossover ranges of 55–80 μm. The three-dimensional but chiral and broken z-axis symmetry nature of the photonic quantum ring cavity appears to guarantee such a crossover to the propagation in general. © 2001 American Institute of Physics.

Electronic Resource

1077-3118

AIP Digital Archive

Physics

We report a systematic study of the microstructure and dielectric properties of barium strontium titanate, Ba1−xSrxTiO3, films grown by laser ablation on LaAlO3 substrates, where x=0.1–0.9 at an interval of 0.1. X-ray diffraction analysis shows that when x〈0.4, the longest unit-cell axis is parallel to the plane of the substrate but perpendicular as x approaches 1. Dielectric constant versus temperature measurements show that the relative dielectric constant has a maximum value and that the peak temperatures corresponding to the maximum relative dielectric constant are about 70 °C higher when x≤0.4 but similar when x〉0.4, compared with the peak temperatures of the bulk Ba1−xSrxTiO3. At room temperature, the dielectric constant and tunability are relatively high when x≤0.4 but start to decrease rapidly as x increases. © 2000 American Institute of Physics.

Electronic Resource

1077-3118

AIP Digital Archive

Physics

We have grown epitaxial anatase-TiO2 (001) films on La0.5Sr0.5CoO3 (001) bottom electrodes using pulsed-laser deposition. The small lattice mismatch (0.5%) between the anatase-TiO2 and the La0.5Sr0.5CoO3 makes it possible to grow anatase-TiO2 films with excellent crystallinity on conductive metal oxides. The photovoltaic properties of the epitaxial anatase-TiO2 on the La0.5Sr0.5CoO3 were characterized using a Kelvin probe. The optical band-gap energy was found to be 3.05 eV. The dielectric properties of the epitaxial anatase-TiO2 films were characterized using a capacitor structure of Au/anatase-TiO2/La0.5Sr0.5CoO3 on a LaAlO3 substrate. The dielectric dispersion exhibited a power-law dependence, and the dielectric constant measured at room temperature and 1 MHz was 38. © 2001 American Institute of Physics.

Electronic Resource

1077-3118

AIP Digital Archive

Physics

We have epitaxially grown Ba0.6Sr0.4TiO3 (BST-0.4) thin films on MgO(001) substrates. By inserting a very thin Ba1−xSrxTiO3 (x=0.1–0.7) interlayer between the MgO substrate and the main layer of BST-0.4, we are able to manipulate the degree of the stress in BST-0.4 films. We have controlled the stress states, i.e., the lattice distortion ratio (D=in-plane lattice constant/out-of-plane lattice constant) of the BST-0.4 films by varying the chemical composition of the interlayers. We have found that small variations of D value can result in significantly large changes of dielectric properties. A BST-0.4 film under small tensile stress, which has a D value of 1.0023, shows the largest dielectric permittivity and tunability. © 2001 American Institute of Physics.

Electronic Resource

1089-7550

AIP Digital Archive

Physics

Epitaxial Bi4Ti3O12 (BTO) thin films were deposited on MgO(001) substrates using Pt layers as top and bottom electrodes. In spite of the apparently symmetric capacitor structure, polarization–voltage measurements revealed strong imprint failures and current–voltage measurements showed rectifying behaviors. Imprint pulse tests with a 5 V dc bias and post-annealing treatments suggested that the asymmetric behaviors should be due to interfacial states induced by thermal processes. To probe the interfacial states, capacitance–voltage (C–V) measurements were performed. By fitting the C–V data with a model which describes the Pt/BTO/Pt structure as a series circuit composed of three capacitors, built-in voltages at the top and the bottom interfaces could be determined. Difference in the built-in voltages could explain the imprint failures and the rectifying behaviors. The interfacial states in the BTO capacitors were controlled by varying electrode materials. © 1998 American Institute of Physics.

Electronic Resource

0005-2736

(V. vulnificus) ; Calcium ion ; Colloid-osmotic hemolysis ; Cytolysin ; Hemolysis ; Inhibition

Elsevier Journal Backfiles on ScienceDirect 1907 - 2002

Biology

Chemistry and Pharmacology

Medicine

Physics

Electronic Resource

1476-4687

Nature Archives 1869 - 2009

Biology

Chemistry and Pharmacology

Medicine

Natural Sciences in General

Physics

[Auszug] Non-volatile memory devices are so named because they retain information when power is interrupted; thus they are important computer components. In this context, there has been considerable recent interest in developing non-volatile memories that use ferroelectric thin ...

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