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  • 1990-1994  (169)
  • 1965-1969  (51)
  • 1870-1879  (7)
  • 1
    Electronic Resource
    Electronic Resource
    Spin cast thin films of fullerenes and fluorinated fullerenes: Preparation and characterization by x-ray reflectivity and surface diffuse x-ray scattering (1992)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 71 (1992), S. 5248-5250 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We demonstrate that high quality thin films of fullerenes (C60) and fluorinated fullerenes can be prepared from solution by the spin coating technique on float glass or silicon wafers. The films were characterized by x-ray reflectivity and diffuse x-ray scattering. A systematic study of films of different thicknesses allows estimation of the distance between the fullerenes spheres to be 10.9±1 A(ring) in our C60 films. The C60 film-air surface is very smooth. Annealing in air above 90 °C leads to an irreversible increase of the film thickness, which is attributed, at present, to oxidation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.350583
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  • 2
    Electronic Resource
    Electronic Resource
    Re-evaluation of the derivatives of the half order Fermi integrals (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 73 (1993), S. 7030-7034 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The Fermi integrals of half orders are important in the simulation of semiconductor transport processes. Several of these integrals (−1/2, 1/2, 3/2, 5/2) have been recently retabulated since the 1938 study by McDougall and Stoner [Phil. Trans. Roy. Soc. A 237, 67 (1938)], but the derivatives were not re-evaluated. The original integral values were calculated without the aid of high speed computers by using approximate series evaluation and tabulations of exponentials and zeta functions. In addition, a discrepancy was found in the literature since the original study in 1938. The second derivative of F1/2 has been mistakenly represented as being proportional to a Fermi integral of another order. This article tabulates the half order Fermi integrals from −1/2 to 5/2 over the reduced energy range −5 to 20 in 0.25 increments. The first two derivatives of F−1/2 are also calculated by numerical integration and tabulated to aid in interpolation. It is shown that the second derivative of F1/2 is not proportional to another Fermi integral. A suitable interpolation scheme is proposed to calculate the values of the Fermi integrals of various order to high accuracy over the total reduced energy range.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.352420
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  • 3
    Electronic Resource
    Electronic Resource
    The effects of CdCl2 on the electronic properties of molecular-beam epitaxially grown CdTe/CdS heterojunction solar cells (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 70 (1991), S. 881-889 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Significant improvements in CdTe/CdS solar cell efficiency are commonly observed as a result of a postdeposition CdCl2 dip followed by a 400 °C heat treatment during cell processing which increases CdTe grain size. In this paper, we investigate the electronic mechanisms responsible for CdCl2-induced improvement in cell performance along with possible performance-limiting defects resulting from this process in molecular-beam epitaxy-grown polycrystalline CdTe/CdS solar cells. Current density-voltage-temperature (J-V-T) analysis revealed that the CdCl2 treatment changes the dominant current transport mechanism from interface recombination/tunneling to depletion region recombination, suggesting a decrease in the density and dominance of interface states due to the CdCl2 treatment. It is shown that the change in transport mechanism is associated with (a) an increase in heterojunction barrier height from 0.56 to 0.85 eV, (b) a decrease in dark leakage current from 4.7×10−7 A/cm2 to 2.6×10−9 A/cm2 and, (c) an increase in cell Voc from 385 to 720 mV. The CdCl2 also improved the optical response of the cell. Substantial increases in the surface photovoltage and quantum efficiency accompanied by a decrease in the bias dependence of the spectral response in the CdCl2-treated structures indicate that the CdCl2 treatment improves carrier collection from the bulk as well as across the heterointerface. However, deep level transient spectroscopy measurements detected a hole trap within the CdTe depletion region of the CdCl2-treated devices at Ev + 0.64 eV which is attributed to the formation of VCd-related defects during the annealing process after the CdCl2 dip. J-V-T analysis demonstrated that this trap is the probable source of dominant recombination in the CdCl2-treated cells. An inverse correlation was found between the density of the Ev + 0.64 eV trap and cell Voc, suggesting that the heat treatment with CdCl2 may eventually limit the CdTe/CdS cell performance unless the formation of this defect complex is controlled or eliminated.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.349652
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    Rotational dynamics and orientational melting of C60: A neutron scattering study (1992)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 96 (1992), S. 8631-8633 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Well-defined librational excitations have been observed at energies of 2–3 meV in the low temperature ordered phase of solid C60. These relatively high energies imply a stiff orientational potential below the transition. The sharpness of the peaks indicates that this potential does not depend strongly on the axis of the angular displacement. The modes soften and broaden as the temperature approaches that of the orientational melting transition which occurs when the librational amplitude is a considerable fraction of nearest-neighbor interatomic angles.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.462876
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  • 5
    Electronic Resource
    Electronic Resource
    Molecular orientational dynamics in solid C70: Investigation by one- and two-dimensional magic angle spinning nuclear magnetic resonance (1993)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 99 (1993), S. 7554-7564 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We present the results of 13C nuclear magnetic resonance (NMR) measurements that probe molecular orientational dynamics in solid C70 in the temperature range 223–343 K. Orientational dynamics affect the NMR line shapes and spin–lattice relaxation rates by modulating the 13C chemical shift anisotropy (CSA). Motionally averaged CSA line shapes, determined from both one-dimensional and two-dimensional magic angle spinning NMR spectra, and relaxation rates are determined for each of the five inequivalent carbon sites in the C70 molecule. Comparisons of the results for the five sites provide evidence for rapid uniaxial molecular reorientation in the monoclinic (T≤280 K) and rhombohedral (280≤T≤330 K) phases and rapid isotropic reorientation in the face-centered cubic (T≥330 K) phase. The orientational correlation time is roughly 2 ns at 250 K and of the order of 5 ps at 340 K.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.465685
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  • 6
    Electronic Resource
    Electronic Resource
    A high counting rate parallel-plate gas proportional counter for fluorescence extended x-ray-absorption fine structure studies : Proceedings of the 4th international conference on synchrotron radiation instrumentation (1992)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 63 (1992), S. 837-841 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Gas proportional counters (GPCs) are well suited for fluorescence extended x-ray-absorption fine structure (EXAFS) experiments in the soft x-ray (〈4 keV) region. They have a near unity detection efficiency and offer good energy resolution. Of the different types of GPC, the parallel-plate device is an attractive option for use with synchrotron radiation beam lines where its intrinsically high count rate permits optimum use of the high photon flux available. The development of a parallel-plate gas proportional counter for use on soft x-ray beam lines at the Daresbury synchrotron source is described. This device is demonstrated to have a counting rate in excess of 1 MHz, and data are presented on its performance including its energy resolution, long-term gain stability, and sample EXAFS spectra.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1142622
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  • 7
    Electronic Resource
    Electronic Resource
    A high rate preamplifier for use with a gas proportional counter : Proceedings of the 4th international conference on synchrotron radiation instrumentation (1992)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 63 (1992), S. 842-845 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: In the development of detectors for use with synchrotron radiation, a serious limit to the maximum counting rate is frequently determined by the signal processing speed of the general purpose commercial electronic units that are often used. Therefore, in developing a high speed gas proportional counter for soft x-ray spectroscopy measurements, a major requirement has been for a high rate, low noise preamplifier. A crucial factor in meeting the required processing speed is the ability to separate out the fast electron pulse from the much slower, induced ion afterpulse and to reject the latter. In addition, all gas proportional counters suffer from occasional high voltage breakdown and so the circuit design must provide the sensitive front end of the preamplifier with sufficient transient protection. We present a design for a preamplifier circuit which offers a 30 MHz bandwidth and better than 2500 electrons rms noise. It features pulse shaping which permits the complete rejection of the ion afterpulse and an input protection circuit which has enabled the preamplifier to survive detector breakdown. The preamplifier has a measured gain of 0.6 μV per electron. The fast rise time of the preamplifier has allowed us to investigate the speed of the detector, a primary limitation of which is due to the electron diffusion rate within the counter. We describe an experiment conducted using this preamplifier to reduce the electron drift speed to 〈100 ns.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1142623
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  • 8
    Electronic Resource
    Electronic Resource
    A new asymptotic form for the Laguerre polynomials (1992)
    College Park, Md. : American Institute of Physics (AIP)
    Journal of Mathematical Physics 33 (1992), S. 1666-1671 
    Details
    ISSN: 1089-7658
    Source: AIP Digital Archive
    Topics: Mathematics , Physics
    Notes: A new asymptotic formula in terms of elementary functions is demonstrated for the Laguerre polynomials Lαn(x) in the limit when all three parameters (n,α,x) become large. This asymptotic limit appears in the problem of obtaining the low-field semiclassical approximation from the full quantum mechanical behavior of a two-dimensional electron gas in a magnetic field.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.529694
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  • 9
    Electronic Resource
    Electronic Resource
    THE USE OF AIRBORNE AUXILIARY DATA IN THE RIGOROUS LEAST SQUARES ADJUSTMENT OF A BLOCK OF AERIAL TRIANGULATION (1969)
    Oxford, UK : Blackwell Publishing Ltd
    The @photogrammetric record 6 (1969), S. 0 
    Details
    ISSN: 1477-9730
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Architecture, Civil Engineering, Surveying
    Notes: The problem of incorporating airborne auxiliary data into an aerial triangulation block adjustment is considered. The conclusion is reached that this problem can be most readily solved by the use of a fully rigorous adjustment method. The first order adjustment equations for all types of airborne auxiliary control are developed and the method of incorporating these equations into the block solution is demonstrated. The general computing problems of the aerial triangulation block adjustment are briefly discussed and a method outlined for the incorporation of tie strips, at any angle across the block, into the adjustment without unduly increasing the storage requirements for the solution. The problem of correctly weighting the different types of available data is discussed. The paper concludes with a demonstration of the improved accuracy possible if precise aerial triangulation data are combined with apparently crude absolute airborne data.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1477-9730.1969.tb00953.x
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  • 10
    Electronic Resource
    Electronic Resource
    IMPRESSIONS OF LISBON (1965)
    Oxford, UK : Blackwell Publishing Ltd
    The @photogrammetric record 5 (1965), S. 0 
    Details
    ISSN: 1477-9730
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Architecture, Civil Engineering, Surveying
    Notes: Four authors review the activities of the seven Commissions of the I.S.P. at the Xth International Congress, Lisbon, 1964.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1477-9730.1965.tb00390.x
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