Search Results - (Author, Cooperation:C. C. Chang)

2018-03-06

American Physical Society (APS)

0556-2821

1089-4918

Physics

Lattice field theories, lattice QCD

2018-10-26

American Physical Society (APS)

0031-9007

1079-7114

Physics

Nuclear Physics

2016-03-17

Nature Publishing Group (NPG)

0028-0836

1476-4687

Biology

Chemistry and Pharmacology

Medicine

Natural Sciences in General

Physics

Acetates/*pharmacology/therapeutic use ; Acetyl-CoA C-Acetyltransferase/antagonists & ; inhibitors/deficiency/genetics/metabolism ; Animals ; Atherosclerosis/drug therapy ; CD8-Positive T-Lymphocytes/*drug effects/*immunology/metabolism ; Cell Membrane/drug effects/metabolism ; Cholesterol/*metabolism ; Esterification/drug effects ; Female ; Immunological Synapses/drug effects/immunology/metabolism ; Immunotherapy/*methods ; Male ; Melanoma/*drug therapy/*immunology/metabolism/pathology ; Mice ; Programmed Cell Death 1 Receptor/antagonists & inhibitors/immunology ; Receptors, Antigen, T-Cell/immunology/metabolism ; Signal Transduction/drug effects ; Sulfonic Acids/*pharmacology/therapeutic use

2018-10-09

The American Society for Pharmacology and Experimental Therapeutics

0022-3565

1521-0103

Medicine

article

2010

Führungsstil ; Bindung ; Leistungsorientierung ; Zufriedenheit ; Gruppenarbeit ; Qualitätsmanagement ; Vergütung ; Arbeit ; Weiterbildung ; Mitarbeiter ; Taipei

Total quality management & business excellence, Bd. 21 (2010) H. 11, S. 1299-1314, 1478-3363

English

2018-06-23

BMJ Publishing

2044-6055

Medicine

Open access, Pathology

1089-7550

AIP Digital Archive

Physics

In situ superconducting YBa2Cu3O7−x films with Tc0 up to 87 K and Jc, 77 K up to 6×104 A/cm2 were prepared on Si substrates with MgAl2O4 and BaTiO3 double-buffer layers. The epitaxial relations between various layers were established by transmission electron microscopy. The MgAl2O4 layer is heavily faulted. The subsequent BaTiO3 layer stops most of the faults, provides a template for the YBa2Cu3O7−x growth, and partially screens off the stress due to different thermal expansion coefficients. The microstructure of the YBa2Cu3O7−x layer is very similar to that of the films deposited directly on SrTiO3, exhibiting a homogeneous heavily faulted single-crystal-like structure free from secondary phases and grain boundaries. The slight degradation of the transport properties is attributed to residual thermal stress.

Electronic Resource

1089-7550

AIP Digital Archive

Physics

The fundamental electromagnetic properties of left-handed materials (LHMs) are reviewed and verified by finite-element method full-wave analysis using rectangular waveguide structures loaded by a LHM and adopting an effective medium approach. The negative phase velocity, positive intrinsic impedance, and modified boundary conditions at an interface with a right-handed medium are verified by loading a waveguide section with a LHM that has edges perpendicular to the waveguide axis. In addition, the negative angle of refraction is demonstrated by loading the junction of a T-junction waveguide with a LHM having one edge 45° with respect to the waveguide axis. These properties are shown by the evolution of wave fronts in the LHM and by analysis of the S-parameters of the waveguide structures. © 2001 American Institute of Physics.

Electronic Resource

1089-7550

AIP Digital Archive

Physics

Photoreflectance is used to investigate the band gap, built-in electric field, and surface Fermi level of a series of lattice-matched In0.52Al0.48As surface-intrinsic n+ structures having different undoped layer thicknesses. Experimental results indicate that, although the built-in electric field depends on the undoped layer thickness, there is a range of thickness within which the surface Fermi level is weakly pinned. From the dependence of electric field and surface Fermi level on the undoped layer thickness, we can determine that the surface states distribute over two separate regions within the energy band gap. The densities of the surface states are evaluated as well. Moreover, the dependence of the built-in electric field on undoped layer thickness is converted into the dependence of surface state density on the surface Fermi level in order to theoretically and exactly calculate the energy spectrum of the surface state density using a Guassian distribution function. The center and width of the distribution near the conduction band are obtained from the fitting parameters. © 2001 American Institute of Physics.

Electronic Resource

1089-7550

AIP Digital Archive

Physics

Lead-zirconate-titanate [Pb(Zr52Ti48)O3,PZT] thin films, 0.5 μm thick, were deposited onto Pt/Si substrate at room temperature using the radio frequency planar magnetron sputtering technique. A perovskite structure in the PZT thin film was obtained after the annealing processes. The annealing temperature varied from 650 to 750 °C in this experiment to find the optimized annealing temperature. Using x-ray diffraction analysis, the lowest full width of the half maximum (110) plane was 0.23° for the sample at 650 °C annealing temperature. The values of the remanent polarization Pr and coercive field Ec of the PZT thin film were 100 nC cm−2 and 0.6 kV cm−1, respectively, at 60 Hz. The measured pyroelectric coefficient in 0.5 μm thin films was 3.12×10−4 C/m2 K at 50 °C. Their dielectric constant and loss tangent were 494 and 0.072, respectively, at 1 kHz. The surface structure of the PZT thin film was examined using scanning electron microscopy and the grain size was in the range of 0.08–0.14 μm. © 2000 American Institute of Physics.

Electronic Resource

1077-3118

AIP Digital Archive

Physics

Critical current densities (Jc) in YBa2Cu3O7−x films made at deposition rates from 0.1 to 14.5 nm/s (∼50 μm/h) were measured using a direct transport method. As the deposition rate was increased by two orders of magnitude, the films exhibited no marked degradation in current carrying capability with Jc of ∼4×106 A/cm2 at 77 K and zero field. Jc for all the films showed similar behavior under a magnetic field up to 8 T, although extra structural defects were found in the films deposited at the higher rates. The results from this experiment indicate the feasibility for coating wires, tapes, and other macroscopic shapes with high Tc superconductors using proper vapor deposition techniques.

Electronic Resource

1077-3118

AIP Digital Archive

Physics

The origin of surface outgrowths in c-axis oriented superconducting Y-Ba-Cu-O thin films has been identified. We find that a,b-axis regions nucleate heterogeneously at second phase regions and rapidly grow outward, leading to the formation of lenticular-shaped outgrowths. The second phase has been identified by electron diffraction and high-resolution electron microscopy to be the Y1Ba3Cu2O7−x phase that forms as microscopic platelet-shaped precipitates on the a-b plane. The heterogeneous nucleation of such outgrowths is general and has been observed in both in situ sputtered and laser-deposited films. It is probably related to the ledge growth mechanism of the c-axis oriented Y-Ba-Cu-O thin film and to the precise overall composition of the film and needs to be studied in detail in order to produce films with smooth surfaces.

Electronic Resource

1077-3118

AIP Digital Archive

Physics

A new source of cadmium diffusion in In0.53Ga0.47As has been developed. Langmuir–Blodgett (LB) deposited monolayers of cadmium arachidate have been used as a source of cadmium. The LB film has been characterized by grazing incidence infrared spectroscopy and Auger electron spectroscopy. Acceptor profiles obtained by differential Hall technique are presented. Highly doped (NA =2×1019 cm−3) shallow (xj ≈0.1–0.4 μm), p+-n junctions are obtained. Mesa-type p-i-n diodes with 125 μm diameter, ideality factor =1.3, Idark =5 nA at 20 V reverse bias, and Vbreakdown =30 V have been fabricated.

Electronic Resource

1077-3118

AIP Digital Archive

Physics

X-ray photoelectron spectroscopy reveals that the remarkable electronic quality of GaAs/sulfide interfaces can be ascribed to the formation of AsxSy phases which grow on an oxide-free GaAs surface. While one of these phases is akin to As2S3, another shows significant in-plane S—S bonding. Raman experiments indicate that the band bending on this disulfide- terminated surface has been reduced to 0.12 eV.

Electronic Resource

1077-3118

AIP Digital Archive

Physics

The microstructure of in situ epitaxially grown Y-Ba-Cu-O thin films on (001) SrTiO3 substrates was studied using cross-sectional transmission electron microscopy. The films, prepared by pulsed laser deposition at substrate holder temperature of 650 °C without post-annealing, exhibit zero resistivity above 90 K and critical currents exceeding 106 A/cm2 at 77 K. The films are of heavily faulted single crystalline structure with the c axis approximately perpendicular to the substrate (001) surface. We suggest that, due to the fast quenching and low substrate temperature, crystalline defects and chemical fluctuations are locked into a faulted structure after each laser pulse. Despite their rather imperfect microstructure, the films are free from macroscopic grain boundaries and secondary phases and possess superb superconducting properties.

Electronic Resource

1077-3118

AIP Digital Archive

Physics

Superconducting Y1Ba2Cu3Ox films 300 nm thick with local surface roughness 〈5 nm have been prepared by laser deposition at 650 °C and subsequent heat treatments at 450 °C; highest zero resistance temperature was above 85 K. Smooth topography and low-temperature processing are crucial for device fabrication. These films are crack-free and density of particles with 〉1 μm diameter was 〈10/cm2. We suggest that an effective increase in surface temperature and deposition directly in the orthorhombic phase contributes to film quality.

Electronic Resource

1077-3118

AIP Digital Archive

Physics

Thin superconducting films of Y-Ba-Cu-O were prepared at 650 °C using the pulsed laser deposition technique. The as-deposited films were fully superconducting at low temperature (30 K). After annealing in oxygen at 450 °C for 3 h, the films exhibited superconductivity with zero resistance at temperatures as high as 83 K. Film-substrate interface reaction was minimal as revealed by Rutherford backscattering and Auger electron spectrometry. These films processed at such low temperatures are also found to have excellent planar surface morphology and high critical current density.

Electronic Resource

1077-3118

AIP Digital Archive

Physics

One problem with the growth of high quality c-axis oriented YBa2Cu3O7−x films is the tendency of the film surface to become rough. We studied the film growth mechanism as a function of deposition rate using pulsed laser deposition. These films form by the classic nucleation and growth process; the thickness at which the nucleated islands coalesce increased with decreasing deposition rate. The film has pinholes prior to coalescence and nucleates outgrowths during coalescence. The outgrowths enlarge rapidly because they contain materials and crystallographic directions with growth rates faster than that of the c-axis film. A smooth surface is obtained if the substrate temperature and deposition rate are chosen such that coalescence is just completed at the final film thickness. We observed the outgrowths nucleating at coalescence and propose that certain defects, related to the c-axis growth habit, may be the fundamental cause of outgrowth formation. Outgrowths have not been observed in a-axis films. Outgrowths are easily confused with the particulate deposition problem associated with laser deposition. In these experiments, the particulate problem was essentially eliminated by using freshly polished targets for each run.

Electronic Resource

1077-3118

AIP Digital Archive

Physics

Superlattices of YBa2Cu3O7−x/YyPr1−yBa2Cu3O7−x(y=0.8 and 0.0) have been successfully grown in situ on MgO and LaAlO3 by using a multitarget pulsed laser deposition system. Satellite peaks have been observed in x-ray diffraction for the superlattices with modulation wavelengths from about few tens of angstroms to few hundred angstroms. The x-ray diffraction measurements also indicate that the multilayers have c axis normal to the substrates. Good crystallinity has been observed in the superlattices with He ion backscattering minimum yields of about 10%, indicating highly oriented growth. The presence of a periodic layer structure was further confirmed by the observation of composition oscillations in these structures by secondary-ion mass spectrometry.

Electronic Resource

1077-3118

AIP Digital Archive

Physics

For crystalline advanced materials, such as the high transition temperature oxide superconductors, the growth of defect-free crystals is often the most sought after desideratum because it opens the doors to fundamental studies and the development of practical applications. We report the observation of YBa2Cu3O7−x(123) thin films having unprecedented structural perfection, at temperatures near 700 °C on [001] LaAlO3. The film's c axis is in the surface plane, unlike films grown at higher temperatures. This orientation has important advantages for device applications and fundamental studies. The Tc,0 is only 70 K, presumably due to oxygen deficiency caused by thermal stresses; if so, it should be possible to raise the Tc,0 by relieving these stresses.

Electronic Resource