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  • American Institute of Physics (AIP)  (96)
  • Cell Press  (28)
  • 2000-2004  (58)
  • 1995-1999  (66)
  • 1
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Silicon (Si) thin films with very-low defect density for solar cells were fabricated by using high-speed (0.7–4.5 mm/s) zone-melting crystallization (ZMC) of amorphous-silicon (a-Si) thin films, resulting in films that had defects below the detection limit of electron spin resonance (ESR). In this letter, poly-crystalline silicon (poly-Si) films for zone-melting recrystallization (ZMR) and a-Si films for ZMC were each sandwiched between two SiO2 films. The Si films were 0.3–2.0 μm thick, the top SiO2 films were 0.35–1.5 μm thick, and the bottom SiO2 films were 0.18–1.2 μm thick. The a-Si ZMC films had higher crystal quality than did the poly-Si ZMR films. Over 90% of the grains in the a-Si ZMC films had preferred (100) orientation when the films were formed at scan speeds 0.7–4.5 mm/s. Transmission electron microscopy (TEM) revealed that neither distinct grain boundaries nor defects were visible in the a-Si ZMC films within the 9-μm-diam observation field. The a-Si ZMC films fabricated from the a-Si films with the thickness smaller than 1 μm had no voids. Such a low defect density indicates that silicon thin-film solar cells with high efficiency can be fabricated by using such very-low defect density silicon thin films. © 2001 American Institute of Physics.
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  • 2
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 102 (1995), S. 7902-7909 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The unimolecular dissociation of trichloroethylene in its electronic ground state has been investigated using an infrared multiphoton dissociation combined with photofragmentation translational spectroscopy to measure product translational energies. The main reaction channel was found to be HCl elimination on the basis of observed product time-of-flight (TOF) spectra. A center-of-mass translational energy distribution for this channel provides direct evidence for competition between two channels, three- and four-centered HCl eliminations. Cl elimination was found to be a minor but significant channel from observed Cl+ and C2HCl+TOF spectra. The branching ratios were determined as 0.28, 0.55, and 0.17 for the three- and four-centered HCl eliminations and the Cl elimination, respectively. The three-centered channel exhibits a "statistical'' translational energy distribution which is typical for a reaction with no potential energy barrier in the reverse reaction, that is to say, no exit barrier reaction. In contrast, the four-centered channel exhibits a "nonstatistical'' translational energy distribution having a peak at around 2 kcal/mol in energy, indicating that a significant exit barrier exists in the channel. The fraction of potential energy converted to translational energy was estimated to be around 10%. Ab initio calculations at the QCISD(T)/6-311+G**//MP2(FC)/6-31G* level were employed to confirm the reaction mechanism. The agreement in the energetics is quite good. © 1995 American Institute of Physics.
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  • 3
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 114 (2001), S. 1617-1623 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Photofragment translational spectroscopy of CBrClF2 at 157.6 nm was carried out using a crossed laser-molecular beams technique. Detected species are Br, Cl, and CF2. From the analyses of time-of-flight (TOF) spectra for these three species, the molecules were found to dissociate competitively through CBrF2+Cl, CClF2+Br, and CF2+Br+Cl channels with the branching ratio of 1.0:1.6−0.22+0.13:0.87−0.18+0.13. All of the CClF2 and CBrF2 radicals were found to dissociate spontaneously to produce Cl or Br+CF2, respectively. The angular distributions of these secondary products were found to be anisotropic. These fast secondary reactions are discussed on the basis of the calculated dissociation rates and rotational frequencies. © 2001 American Institute of Physics.
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  • 4
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 114 (2001), S. 1624-1630 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Photodissociation dynamics from the repulsive nσC−X* (X=Cl,Br) states of CBrClF2 has been studied by propagating wave packets on the two diabatic potential energy surfaces obtained by an approximate diabatization of ab initio complete active space self-consistent field (CASSCF) potential energy surfaces. The diabatization was carried out so as to eliminate the transition-dipole moment between the two excited states. The results have confirmed the occurrence of simultaneous triple dissociation CBrClF2→Br+Cl+CF2 observed in the 157.6 nm photolysis of CBrClF2. The triple dissociation has been found to occur on both the upper and lower adiabatic surfaces with oscillation in the population in between. © 2001 American Institute of Physics.
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  • 5
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 86 (1999), S. 4354-4359 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: CuInSe2 (CIS) films with Cu/In ratios of γ=0.82–1.79 have been grown on a GaAs (001) substrate by molecular beam epitaxy. Piezoelectric photoacoustic (PPA) measurements were carried out from liquid helium to room temperature to investigate nonradiative carrier recombination processes in comparison with photoluminescence (PL) measurements which directly detected radiative carrier recombination processes. Three PPA signal peaks which corresponded to band gap energies of the CIS (AB and C bands) and the GaAs substrate, were clearly obtained between liquid helium and room temperatures. A free-exciton emission line was observed up to 200 K in the PL spectra. Two additional peaks on intrinsic defects which are Cu vacancy (VCu) and interstitial In (Ini) were observed in the In-rich CIS samples. The PPA measurements were useful in investigating the defect levels and the band gap energy in the CIS/GaAs thin films. © 1999 American Institute of Physics.
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  • 6
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 3 (1996), S. 177-191 
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The cold fluid theory of the Pierce beam–plasma system is modified by the incorporation of warm plasma effects. The controlling parameter α in the cold theory, where α=Lωp/V0, L=diode width, ωp=plasma frequency, and V0=beam velocity at injection, is replaced in the warm theory by an effective value of α involving the thermal velocity. The theory is verified by means of a fluid simulation code; the phase states for a cold plasma, including the chaotic state, are recovered for a warm plasma, but with a shift in values of the bifurcation parameter. Furthermore, in order to include plasma kinetic effects, an extensive electrostatic particle simulation code is developed to model the Pierce system. Among the new physical effects arising in this particle model are the local and global thermalization of electrons by electrostatic waves, and blocking oscillations due to particle reflection and trapping. As the parameter α is decreased, the electric field at the injection point typically changes state as follows: blocking oscillation→small fluctuations→quasisteady oscillation→prechaotic oscillation→chaos→blocking oscillation→dc electric field. The mechanics of chaotic oscillations in the Pierce system are examined with particular regard to kinetic effects. © 1996 American Institute of Physics.
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  • 7
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 2 (1995), S. 349-351 
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The bootstrap current Jb=−IcP'B/〈B2〉 and χi= (square root of)2NνiMiTi(Ic/e)2〈1/B2〉/||∇ψ ||2 are valid for both the banana and the Pfirsch–Schlüter regimes for any finite value of the collision frequency at a radius where the local aspect ratio A approaches unity. Here, I=RBt with R the major radius, Bt the toroidal magnetic field strength, and the prime denoting the derivative with respect to the poloidal flux ψ. Thus, the bootstrap current does not vanish, even in the collisional regime, when A approaches unity. The physical reason for this dramatic result is that the magnitudes of the electron and ion parallel viscosity approach infinity as A approaches unity. This also indicates that the conventional theory underestimates the magnitude of bootstrap current in an ultralow-aspect-ratio tokamak. © 1995 American Institute of Physics.
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  • 8
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The bifurcation nature of the electrostatic structure is studied in the toroidal helical plasma of the Compact Helical System (CHS) [K. Matsuoka et al., Proceedings of the 12th International Conference on Plasma Physics and Controlled Nuclear Fusion Research, Nice, 1988 (International Atomic Energy Agency, Vienna, 1989), Vol. 2, p. 411]. Observation of bifurcation-related phenomena is introduced, such as characteristic patterns of discrete potential profiles, and various patterns of self-sustained oscillations termed electric pulsation. Some patterns of the electrostatic structure are found to be quite important for fusion application owing to their association with transport barrier formation. It is confirmed, as is shown in several tokamak experiments, that the thermal transport barrier is linked with electrostatic structure through the radial electric field shear that can reduce the fluctuation resulting in anomalous transport. This article describes in detail spatio-temporal evolution during self-sustained oscillation, together with correlation between the radial electric field and other plasma parameters. An experimental survey to find dependence of the temporal and spatial patterns on plasma parameters is performed in order to understand systematically the bifurcation property of the toroidal helical plasma. The experimental results are compared with the neoclassical bifurcation property that is believed to explain the observed bifurcation property of the CHS plasmas. The present results show that the electrostatic property plays an essential role in the structural formation of toroidal helical plasmas, and demonstrate that toroidal plasma is an open system with a strong nonlinearity to provide a new attractive problem to be studied. © 2000 American Institute of Physics.
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  • 9
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 3 (1996), S. 965-970 
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: An approximate analytic expression for plasma viscosity in finite aspect ratio tokamaks is constructed from all the asymptotic limits. The resultant viscosity coefficient is compared with the numerical results of the solution of the linearized drift kinetic equation. Neoclassical fluxes are reformulated in terms of the viscosity and friction coefficients. These fluxes can be employed to study the omnigeneous property of high-beta small, or large aspect ratio tokamaks. © 1996 American Institute of Physics.
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  • 10
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 91 (2002), S. 5213-5220 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Narrow (≥95 nm) and extremely thin (∼7 nm) heavily phosphorous-doped polycrystalline-silicon (poly-Si) wires were fabricated by low-pressure chemical vapor deposition. The electrical conduction mechanism has been investigated at low temperatures (down to ∼5 K), and observation by transmission electron microscopy (TEM) was carried out. Single-electron effects such as Coulomb oscillations have been observed at temperatures up to 80 K. The size of the island in the poly-Si wires was estimated from the electrical properties, and it was in the same order as the grain size of the poly-Si measured by TEM. A maximum tunnel barrier height of ∼26 meV of the poly-Si grain boundary is obtained from the temperature dependence of the conductance of the sample. A model for the electronic conduction through multiple islands was proposed from the width dependence of their electrical properties. © 2002 American Institute of Physics.
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