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  • 1
    Electronic Resource
    Electronic Resource
    Ab initio theoretical study on the reactions of a hydrogen molecule with small platinum clusters: A model for chemisorption on a Pt surface (1988)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 88 (1988), S. 5759-5769 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Reactions of a hydrogen molecule with small platinum clusters Ptn (n=1,2,3) are studied theoretically by ab initio methods. This provides a cluster model study for hydrogen chemisorption on a Pt surface. The results suggest that the Pt atom and the linear Pt3 cluster will react with H2 and dissociatively adsorb it, making two Pt–H bonds, whereas the Pt2 cluster will not react with H2 because of a high energy barrier. The dissociative adsorption of a hydrogen molecule occurs at a side-on, on-top site of a surface Pt atom and molecular adsorption does not seem to occur. Essentially only one Pt atom is involved in the initial adsorption process. These findings are in contrast to the palladium case previously reported. Almost no energy barrier exists for the hydrogen migration from one Pt atom to an adjacent one, with a preference being shown for one H atom on each Pt atom rather than two H atoms on one Pt atom. The heat of adsorption, the stability of the catalytic surface, etc., are best represented by the Pt3–H2 system. Spin–orbit coupling effect is examined for the Pt–H2 system and found to be small for the singlet A1 state which is the most important state for the dissociative adsorption. This effect is important, however, to obtain natural potential curve in the large Pt–H2 separation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.454534
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  • 2
    Electronic Resource
    Electronic Resource
    Cluster expansion of the wave function. Valence and Rydberg excitations and ionizations of pyrrole, furan, and cyclopentadiene (1985)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 83 (1985), S. 723-734 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The symmetry-adapted cluster (SAC) expansion and the SAC-CI theory have been applied to the calculations of the valence and Rydberg excitations and ionizations of the five-membered ring compounds, pyrrole, furan, and cyclopentadiene. For almost all cases, the experimental values were reproduced to within 0.3 eV for the excitation energy, and to within 0.5–0.7 eV for the ionization potential. We have given several new assignments for the excitation spectra of pyrrole and furan, and the first ab initio assignments for cyclopentadiene. However, there were remarkable disagreements of about 1.2 eV for the singlet π → π* excitations of 2 1A1 state for furan, and of 1 1B2 state for cyclopentadiene. This is the same tendency as those due to the MRSD-CI method. For ionization potential, our assignments of the peaks are essentially the same as those due to the Green's function method by von Niessen et al., but the present SAC-CI method reproduces the experimental data better than this method.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.449857
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  • 3
    Electronic Resource
    Electronic Resource
    Development of a steady-state microwave ion source with large spherical electrodes for geometrical focusing : The 8th international conference on ion sources (2000)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 71 (2000), S. 1144-1147 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A steady-state electron cyclotron resonance ion source with large spherical electrodes has been developed to study the plasma wall interaction, erosion mechanism, and hydrogen retention of first wall materials in a nuclear fusion reactor. Discharge characteristics of the ion source were studied in terms of microwave power, magnetic field configuration, and gas (H2) pressure. Ion saturation current density Jis of about 21 mA/cm2 near the electrodes (target value is 20 mA/cm2) was achieved with microwave power of 3.0 kW and magnetic field of 2.3 kG at an optimal gas pressure. The measurement of Jis was made by a Langmuir probe. It was found that the dependence of ion saturation current density on the magnetic field was different between high (〉5 mTorr) and low (〈5 mTorr) pressure. The change of the gas inlet position from the center of the plasma production chamber to near the microwave input window gave higher ion saturation current density. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1150410
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  • 4
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    Short minority carrier lifetimes in highly nitrogen-doped 4H-SiC epilayers for suppression of the stacking fault formation in PiN diodes (2016)
    American Institute of Physics (AIP)
    Details
    Publication Date: 2016-09-16
    Description: We investigated the dependency of minority carrier lifetimes on the nitrogen concentration, temperature, and the injected carrier concentration for highly nitrogen-doped 4H-SiC epilayers. The minority carrier lifetimes greatly shortened when the nitrogen concentration exceeded 10 18  cm −3 through enhancing direct band-to-band and Auger recombination and showed a slight variation in the temperature range from room temperature (RT) to 250 °C. The epilayer with a nitrogen concentration of 9.3 × 10 18 cm −3 exhibited a very short minority carrier lifetime of 38 ns at RT and 43 ns at 250 °C. The short minority carrier lifetimes of the highly nitrogen-doped epilayer were confirmed to maintain the values even after the subsequent annealing of 1700 °C. 4H-SiC PiN diodes were fabricated by depositing a highly nitrogen-doped epilayer as a “recombination enhancing layer” between an n − drift layer free from basal plane dislocations and the substrate. The PiN diodes showed no formation of stacking faults and no increase in forward voltage during current conduction of 600 A/cm 2 (DC), demonstrating that a highly nitrogen-doped buffer layer with a short minority carrier lifetime successfully suppresses the “bipolar degradation” phenomenon.
    Print ISSN: 0021-8979
    Electronic ISSN: 1089-7550
    Topics: Physics
    Published by American Institute of Physics (AIP)
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