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  • American Institute of Physics (AIP)  (31)
  • 1985-1989  (31)
  • 1935-1939
  • 1
    Electronic Resource
    Electronic Resource
    ESR study of optically enhanced phase transition in (BEDT–TTF)3Ta2F11 (1987)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 86 (1987), S. 1780-1788 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We have identified an optically enhanced magnetic phase transition in the newly synthesized organic molecular charge transfer salt, (BEDT–TTF)3Ta2F11 (BEDT–TTF 3/4 bis-ethylenedithiolotetrathiafulvalene) by ESR absorption measurements in the X band microwave region. At room temperature, only a doublet state ESR absorption is observed, but below 30 K several triplet ESR absorptions appear. The orientation dependence of the ESR absorption under illumination at energies near the band gaps in the material (640 nm, T=12 to 5 K, H0〈0.34 T) indicates that there are rapid spin exchange processes with times τe〈10−8 s near 7 to 5 K along certain crystallographic directions with a temperature dependence suggesting spin-lattice relaxation times which proceed via Van Vleck "direct processes.'' This, to our knowledge, is the first case where the magnetic properties of a charge transfer salt are altered by the interaction with photons of energy equal to the band gaps in a low dimensional solid, providing a new, interesting way to investigate these materials.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.452178
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  • 2
    Electronic Resource
    Electronic Resource
    Hydrogen particle diagnostic based on Pd-MOS diode arrays (1988)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 59 (1988), S. 1884-1886 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The reverse-bias current through a Pd-MOS diode changes when hydrogen is present at the diode interface and this effect provides the bias for a solid-state detector to monitor the flux and energy of hydrogen particles emanating from a beam or plasma. The addition of a coating atop the Pd forms a high-pass energy filter and an array of coated Pd-MOS diodes can function as a compact, hydrogen-specific, energy spectrometer. The response characteristics of an Au-coated Pd-MOS diode array have been measured using a low-energy hydrogen ion source. The array has several desirable characteristics for energetic hydrogen detection. Its response is dosimetric, it discriminates between hydrogen irradiations at different energies, and it can be regenerated by heating briefly to 100–200 °C. These properties make Pd-MOS diode arrays attractive candidates for remote plasma-edge flux and energy monitors in fusion devices.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1140042
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  • 3
    Electronic Resource
    Electronic Resource
    NMR pulse response and measurement of the quadrupole coupling constant of I=3/2 nuclei (1986)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 85 (1986), S. 6923-6927 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The rf pulse response of a system of I=3/2 nuclei which experience identical first-order quadrupole splitting is investigated using the density matrix method. A general expression is derived for the time evolution of the in-phase magnetization following a rectangular pulse applied at the center line frequency. The maximum amplitude of the magnetization associated with the center line, and the length of pulse that gives rise to it, are calculated as a function of the ratio of the quadrupole splitting to the amplitude of the rf field. Data obtained for 23Na in a single crystal of NaNO3 are in fairly good agreement with the theoretical form. The theory has been extended to the case where the nuclei are situated at equivalent sites in a polycrystalline sample. The length of pulse that maximizes the amplitude of the FID of 23Na in a powder sample of NaNO3 has been measured as a function of the amplitude of the rf field. The quadrupole coupling constant, found by fitting the data to the theoretical form, is in very good agreement with the accepted value. It is proposed that this method can be widely used to measure the quadrupole coupling constants of I=3/2 nuclei.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.451378
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  • 4
    Electronic Resource
    Electronic Resource
    Time and temperature dependence of instability mechanisms in amorphous silicon thin-film transistors (1989)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 54 (1989), S. 1323-1325 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have measured the time and temperature dependence of the two prominent instability mechanisms in amorphous silicon thin-film transistors, namely, the creation of metastable states in the a-Si:H and the charge trapping in the silicon nitride gate insulator. The state creation process shows a power law time dependence and is thermally activated. The charge trapping process shows a logarithmic time dependence and has a very small temperature dependence. The results for the state creation process are consistent with a model of Si dangling bond formation in the bulk a-Si:H due to weak SiSi bond breaking stabilized by diffusive hydrogen motion. The logarithmic time dependence and weak temperature dependence for the charge trapping in the nitride suggest that the charge injection from the a-Si:H to the nitride is the rate limiting step and not subsequent conduction in the nitride.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.100704
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  • 5
    Electronic Resource
    Electronic Resource
    Synchrotron radiation Bragg angle contour mapping of crack nucleation at grain boundaries (1989)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 65 (1989), S. 2282-2288 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In technical materials a critical step leading to complete macroscopic failure is not the nucleation of cracks in isolated grains, but instead the transmission of rupture from grain to grain until the entire cross section is traversed. It is difficult, in general, to employ the usual microscopic observations which could provide the keys to a comprehensive mechanistic understanding of this problem. It is shown herein that monochromatic synchrotron radiation can be used to provide Bragg angular contour maps in a rapid and precise manner. These maps enable one to quantify the local strain field tensor associated with crack nucleation and propagation through a grain boundary. Based on this analysis it is then a straightforward process to determine the other mathematical properties usually associated with second rank tensors which lead to assessment of critical parameters for crack transmission at the boundary. The application of this analytical technique is experimentally demonstrated by studies of crack formation at grain boundaries in zinc bicrystals.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.343416
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  • 6
    Electronic Resource
    Electronic Resource
    Deep trapping controlled switching characteristics in amorphous silicon thin-film transistors (1989)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 66 (1989), S. 4488-4495 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report transient effects in amorphous silicon thin-film transistors occurring upon switch-on and switch-off, which are controlled by trapping and emission from the deep states in the amorphous silicon. We develop a unifying theoretical description which is applicable to both switch-on and switch-off. The model is based on carrier thermalization to the deep states and includes the spatial dependence of the thermalization process in the band-bending region. The model is able to explain the experimentally observed switch-on and switch-off behavior. In the case of switch-on, electrons are progressively trapped into the deep states in the bulk a-Si:H throughout the entire thickness of the layer. The range of trapping times is large and this leads to a dynamic threshold votage shift and a time dependence of the source-drain current extending between 1 μs and 1 s. In the case of switch-off, two processes occur sequentially. First, there is emission of electrons from the bulk a-Si:H deep states, which leads to a uniform space charge throughout the thickness of the layer. After that, a redistribution of the space charge occurs, leading to the eventual thermal equilibrium space-charge distribution. These processes give rise to two different time constants in the measured decay of the total charge stored in the transistor. Full thermal equilibrium can take several hours to reach.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.343947
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  • 7
    Electronic Resource
    Electronic Resource
    Dual dielectric silicon metal-oxide-semiconductor field-effect transistors as radiation sensors (1989)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 65 (1989), S. 1972-1976 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A new design for radiation-sensing field-effect transistors (RADFETs) is presented, involving the use of very thick silicon nitride layers deposited on top of a high-quality thermal silicon dioxide. In contrast to previous RADFET fabrication procedures, no attempt was made to introduce hole traps into the thermal oxide. Instead the trapping layer at the nitride oxide interface was used to store the positive charge which forms the basis for operation of the RADFET. Data is presented which shows hole transport in the thermal oxide. Models explaining the field dependence of the response and the saturation behavior of the dual dielectric device are given. These RADFETs are more stable than any previously described in the literature and have a sensitivity of 86 μV/rad dose at room temperature.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.342887
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  • 8
    Electronic Resource
    Electronic Resource
    Islands of stability and complex universality relations (1987)
    College Park, Md. : American Institute of Physics (AIP)
    Journal of Mathematical Physics 28 (1987), S. 60-63 
    Details
    ISSN: 1089-7658
    Source: AIP Digital Archive
    Topics: Mathematics , Physics
    Notes: For complex mappings of the type z→λz(1−z), universality constants α and δ can be defined along islands of stability lying on filamentary sequences in the complex λ plane. As the end of the filament is approached, asymptotic values αN∼λN−1∞, δN/α2N∼1 are attained, where μ∞=λ∞(λ∞−2)/4, is associated with the limiting form of the universal function for that sequence, g(z)=1−μ∞z2. These results are complex generalizations of the real mapping case (applying to tangent bifurcations and windows of stability) where μ∞=2 and δ/α2→ (2)/(3) correspond to the filament running along the real axis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.527808
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  • 9
    Electronic Resource
    Electronic Resource
    Application of generating function techniques to Lie superalgebras (1985)
    College Park, Md. : American Institute of Physics (AIP)
    Journal of Mathematical Physics 26 (1985), S. 901-912 
    Details
    ISSN: 1089-7658
    Source: AIP Digital Archive
    Topics: Mathematics , Physics
    Notes: The construction of generating functions for multiplicities of irreducible representations of Lie superalgebras from generating functions for characters is examined, and applied in order to obtain polynomial tensors and branching rules. Problems arising because of the existence of typical and atypical representations are discussed in detail. The techniques are applied to osp(1,2), spl(1,2), osp(3,2), and osp(4,2).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.526546
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  • 10
    Electronic Resource
    Electronic Resource
    A pair of commuting scalars for G(2) &supuline; SU(2)×SU(2) (1985)
    College Park, Md. : American Institute of Physics (AIP)
    Journal of Mathematical Physics 26 (1985), S. 894-900 
    Details
    ISSN: 1089-7658
    Source: AIP Digital Archive
    Topics: Mathematics , Physics
    Notes: G(2) &supuline; SU(2)×SU(2) is a two-missing-labels problem, and therefore in order to give a complete and orthogonal specification of states of irreducible representations of G(2) in an SU(2)×SU(2) basis, one needs to find a pair of commuting Hermitian operators which are scalar with respect to the SU(2)×SU(2) subalgebra. A theorem due to Peccia and Sharp states that there are, apart from the Lie algebra invariants, twice as many functionally independent scalars as missing labels. Here two commuting SU(2)×SU(2) scalars are obtained, both of sixth order in the G(2) basis elements. They are in fact combinations of five scalars of different tensorial types, indicating that the functionally independent ones are in general insufficient to provide the lowest-order commuting scalars. An expression for the sixth-order invariant of G(2) is also obtained.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.526545
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