Search Results - (Author, Cooperation:T. W. Kim)

2011-09-24

American Association for the Advancement of Science (AAAS)

0036-8075

1095-9203

Biology

Chemistry and Pharmacology

Computer Science

Medicine

Natural Sciences in General

Physics

*Air Pollutants ; Atmosphere/*chemistry ; Ecosystem ; Nitrates/*analysis ; Nitrogen/*analysis ; Pacific Ocean ; Phosphorus/analysis ; Seawater/*chemistry

2014-11-29

American Association for the Advancement of Science (AAAS)

0036-8075

1095-9203

Biology

Chemistry and Pharmacology

Computer Science

Medicine

Natural Sciences in General

Physics

Asia ; Humans ; Nitrates/*analysis ; Nitrogen/*analysis ; Pacific Ocean ; Phosphates/analysis ; Seawater/*chemistry ; Water Pollutants, Chemical/*analysis ; *Water Pollution

2014-02-15

American Association for the Advancement of Science (AAAS)

0036-8075

1095-9203

Biology

Chemistry and Pharmacology

Computer Science

Medicine

Natural Sciences in General

Physics

2011-06-15

Nature Publishing Group (NPG)

0028-0836

1476-4687

Biology

Chemistry and Pharmacology

Medicine

Natural Sciences in General

Physics

Arabidopsis/*chemistry/*metabolism ; Arabidopsis Proteins/*chemistry/*metabolism ; Binding Sites ; Brassinosteroids ; Cholestanols/chemistry/*metabolism ; Crystallography, X-Ray ; Enzyme Activation ; Hydrophobic and Hydrophilic Interactions ; Models, Molecular ; Protein Binding ; Protein Folding ; Protein Kinases/*chemistry/*metabolism ; Protein Structure, Tertiary ; Steroids, Heterocyclic/chemistry/*metabolism ; Structure-Activity Relationship ; Substrate Specificity

2016-04-29

Nature Publishing Group (NPG)

0028-0836

1476-4687

Biology

Chemistry and Pharmacology

Medicine

Natural Sciences in General

Physics

Biomimetic Materials/chemistry ; Biomimetics ; Cactaceae/metabolism ; Desiccation ; Dialysis ; Electrochemistry ; Humidity ; Hydrophobic and Hydrophilic Interactions ; *Membranes, Artificial ; *Nanotechnology ; Plant Stomata/metabolism ; Polymers/*chemistry ; Protons ; Surface Properties ; Temperature ; Water/*analysis

2015-02-20

Nature Publishing Group (NPG)

0028-0836

1476-4687

Biology

Chemistry and Pharmacology

Medicine

Natural Sciences in General

Physics

2012-02-07

Nature Publishing Group (NPG)

0028-0836

1476-4687

Biology

Chemistry and Pharmacology

Medicine

Natural Sciences in General

Physics

Arabidopsis/*drug effects/*enzymology/genetics/growth & development ; Arabidopsis Proteins/antagonists & inhibitors/genetics/*metabolism ; Brassinosteroids/*pharmacology ; Glycogen Synthase Kinase 3/antagonists & inhibitors/genetics/*metabolism ; MAP Kinase Kinase Kinases/metabolism ; MAP Kinase Signaling System/*drug effects ; Mitogen-Activated Protein Kinase Kinases/metabolism ; Phosphorylation/drug effects ; Plant Stomata/*drug effects/enzymology/genetics/*growth & development ; Plants, Genetically Modified ; Protein Kinases/genetics/*metabolism ; Protein-Serine-Threonine Kinases/genetics/metabolism ; Receptors, Cell Surface/genetics/metabolism ; Tobacco

2011-01-29

American Association for the Advancement of Science (AAAS)

0036-8075

1095-9203

Biology

Chemistry and Pharmacology

Computer Science

Medicine

Natural Sciences in General

Physics

Amino Acid Sequence ; Animals ; Bacteria/enzymology/*genetics/isolation & purification/metabolism ; Bacterial Proteins/chemistry/genetics/metabolism ; *Biomass ; Carbohydrate Metabolism ; Cattle/*microbiology ; Cellulase/genetics/metabolism ; Cellulases/chemistry/*genetics/metabolism ; Cellulose/*metabolism ; Cellulose 1,4-beta-Cellobiosidase/genetics/metabolism ; Genes, Bacterial ; Genome, Bacterial ; *Metagenome ; Metagenomics/methods ; Molecular Sequence Annotation ; Molecular Sequence Data ; Poaceae/microbiology ; Rumen/metabolism/*microbiology ; Sequence Analysis, DNA

2018-11-16

The American Association for Cancer Research (AACR)

1078-0432

1557-3265

Medicine

1089-7550

AIP Digital Archive

Physics

Photoluminescence measurements were carried out in order to investigate the dependence of the optical properties of p-Cd0.96Zn0.04Te single crystals on hydrogen passivation conditions. After the p-Cd0.96Zn0.04Te was annealed at 500 °C in a Cd atmosphere for 5 h, the luminescence due to the recombination of the electrons in the conduction band with acceptors (eA°) and to the donor–acceptor pair (DAP) transitions disappeared. After the p-Cd0.96Zn0.04Te was hydrogenated, the intensity of the exciton luminescence increased so that the (eA°) and DAP peaks related to the Cd vacancies disappeared, and the defect band in the low energy range between 1.4 and 1.5 eV also vanished. These results indicate that hydrogen atoms passivated not only shallow donors but also deep acceptor impurities and that the hydrogen atoms were separated from the hydrogenated samples at 400 °C due to their thermal energy.

Electronic Resource

1089-7550

AIP Digital Archive

Physics

Metalorganic chemical vapor deposition of Al2O3 using Al(O-C3H7)3 and N2O via pyrolysis was investigated with the goal of producing Al2O3 epitaxial films on p-Si (100) substrates. Room-temperature capacitance-voltage measurements clearly showed metal-insulator-semiconductor behaviors for the samples with the Al2O3 insulator gate, and the interface state densities at the Al2O3/p-Si interface were approximately 1011 eV−1 cm−2 at the middle of the Si energy gap. Auger depth profiles demonstrated that the Al2O3/Si interface was not abrupt, and transmission electron microscopy verified the formation of an interfacial layer in the Al2O3/Si interface and the formation of a polycrystalline Al2O3 thin film. These results indicated that the failure to form Al2O3 epitaxial films was due to the formation of an interfacial layer prior to the growth of the Al2O3 layer.

Electronic Resource

1089-7550

AIP Digital Archive

Physics

Photoluminescence measurements were carried out to investigate the dependence of the optical properties of p-CdTe and p-Cd0.96Zn0.04Te on various relative concentrations of bromine in a mixture of methanol and bromine. As the bromine concentration increased, the intensity of the luminescence increased; additionally, an exciton bound to a neutral acceptor (A°X) peak at 1.588 eV in p-CdTe was resolved into an exciton bound to neutral donor (D°X) peak at 1.592 eV and an A°X peak. The mixed bands of the 1.574 and 1.546 eV peaks were well resolved by using an etching bromine concentration of 2%; in particular, the intensities of the D°X and 1.574 eV peaks increased as much as five and seven times, respectively. The intensity of the peak at 1.48 eV related to defects also increased. The intensity of A°X at 1.609 eV in p-Cd0.96Zn0.04Te changed slightly with the bromine concentration. The intensities of the luminescence peaks due to the recombination of the electrons in conduction band with acceptors and to the defect relation did not vary. These results indicated that the number of Cd vacancies could be reduced due to the addition of Zn.

Electronic Resource

1089-7550

AIP Digital Archive

Physics

The growth of high quality CdTe epitaxial films on p-InSb(111) by a simple method of temperature gradient vapor transport deposition was carried out to investigate the possibility of the existence of a two-dimensional electron gas with high mobility at CdTe/InSb heterointerfaces. From the x-ray diffraction analysis, the grown layer was found to be a CdTe epitaxial film. Photoluminescence measurements at 15 K showed that a CdTe film grown on InSb(111) in the temperature range between 180 and 280 °C appeared to have an optimum crystal perfection at a substrate temperature of about 245 °C. These results also indicated that the CdTe films grown above 245 °C contained a significant problem due to interdiffusion from the InSb substrates during the growth.

Electronic Resource

1089-7550

AIP Digital Archive

Physics

A thermally stimulated current (TSC) technique is applied to examine the activation energy, capture cross sections, escape frequency, and trap polarity in amorphous Se (a-Se) implanted with low energy (〈20 keV) Li+ ions. TSC glow curves for Li+ -ion-implanted a-Se show two peaks near 230 and 330 K. The value of δ/ω is 0.46 for 230 K, which means that the thermally stimulated currents are due to the first-order kinetics. The trap activation energy levels obtained by peak shape method and various heating rate methods are distributed from 0.22 to 0.33 eV for the 230-K peak and to 1.42 eV for the 330-K peak. The values of the capture cross section and the escape frequencies are 2.75×10−19 cm2 and 5.5×105 s−1 for the 230-K peak, and 5.75×10−20 cm2 and 6.43×105 s−1 for the 330-K peak, respectively. It is found that the trapped charge carriers are mainly holes in Li+ ion-implanted a-Se.

Electronic Resource

1089-7550

AIP Digital Archive

Physics

GaAs films grown on untilted Si substrates and prepared by molecular-beam epitaxy were characterized by low-temperature photoluminescence (PL) spectroscopy. The GaAs layer was irradiated in situ with a 50 keV electron beam during growth. The PL spectrum of the electron-beam-irradiated GaAs/Si consisted of four well-resolved peaks at 1.502, 1.488, 1.471, and 1.434 eV. The peaks at 1.502 and 1.488 eV are related to the intrinsic emissions, and the peaks at 1.471 and 1.434 eV originate from the extrinsic emission band. The full width at half-maximum of the 1.488 eV emission band is only 2.8 meV, which is much smaller than the value obtained from the unirradiated GaAs/Si. The strain induced in the GaAs layer was estimated from the intrinsic peaks observed in the temperature range of 5–200 K. The PL properties of the species after postgrowth treatment, such as rapid thermal annealing are discussed.

Electronic Resource

1089-7550

AIP Digital Archive

Physics

Ferroelectric BaTiO3 thin films were grown on Si(100) substrates at a temperature of 600 °C by in situ metalorganic chemical vapor deposition. X-ray diffraction and transmission electron microscopy results suggested that the 〈110〉 direction of the BaTiO3 preferred oriented films is parallel with the (100) direction of the Si substrates. Auger electron spectroscopy measurements showed that the compositions of the as-grown films were with a uniform distribution throughout the thickness of the films and with a sharp interface. These results indicate that the failure to obtain BaTiO3 epitaxial films was due to the formation of an interfacial amorphous layer prior to the creation of the films.

Electronic Resource

1089-7550

AIP Digital Archive

Physics

Deep trap properties such as activation energy, capture cross section, and polarity in the amorphous selenium bulk are investigated using a thermally stimulated current (TSC). Two peaks are found near 220 and 330 K in the TSC curve, and the activation energies corresponding to these two peaks are distributed from 0.20 to 0.22 eV and from 1.04 to 1.10 eV. It is found that the trapped carriers near the temperature 220 K are mainly holes.

Electronic Resource

1089-7550

AIP Digital Archive

Physics

A computer simulation based on the binary collision approximation has been performed to investigate the Si implantation efficiency, the Si depth profile, and the vacancy formation for Si-implanted GaAs (001) crystals. The results reveal a strong dependence on the incident angle of the Si source. The calculated depth profile of Si agrees well with the experimental results from secondary-ion mass spectroscopy. The simulated distribution of vacancies is shallower than that of Si atoms. Also, the calculated number of Ga vacancies exceeds that of As vacancies, which suggests that the Si atoms easily occupy the Ga sites and are activated as donors.

Electronic Resource

1089-7550

AIP Digital Archive

Physics

A thermally stimulated current technique has been carried out to investigate the defect levels in Si-ion-implanted GaAs. Thermally stimulated current measurements have been performed in the temperature range of 90–300 K, and five deep traps with activation energies of 0.18, 0.20, 0.31, 0.40, and 0.43 eV have been observed. It is considered that the one of the traps (Ea=0.18 eV) shows the optical quenching effect and another trap (Ea=0.20 eV) is related to the damage due to the implanted ions.

Electronic Resource

1089-7550

AIP Digital Archive

Physics

Electronic property variations of a two-dimensional electron gas (2DEG) in modulation-doped step quantum wells due to an embedded potential barrier were studied by performing Shubnikov–de Haas (SdH), Van der Pauw–Hall-effect, and cyclotron resonance measurements on two kinds of InxGa1−xAs/InyAl1−yAs step quantum wells which were one without and the other with an embedded barrier. The fast Fourier transformation results for the SdH data at 1.5 K indicated the electron occupation of two subbands in both step quantum wells. The total electron carrier density and the mobility of the 2DEG in the step quantum well with an embedded barrier were smaller than those in the quantum well without an embedded barrier. The electron effective masses were determined from the slopes of the main peak absorption energies as functions of the magnetic field, and satisfied qualitatively the nonparabolicity effects in both quantum wells. The electronic subband energies, the wave functions, and the Fermi energies were calculated by using a self-consistent method taking into account exchange-correlation effects together with strain and nonparabolicity effects. These present results indicate that the electronic parameters in modulation-doped InxGa1−xAs/InyAl1−yAs step quantum wells are significantly affected by an embedded barrier. © 2002 American Institute of Physics.

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