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  • 1
    Digitale Medien
    Digitale Medien
    Interpretation of transmission electron microscope images of amorphous silicon/germanium and silicon/iron multilayers (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 69 (1991), S. 1371-1376 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: We show that the observed contrast in transmission electron microscope images of multilayer specimens composed of amorphous materials can be understood in terms of the scattering of electrons passing through the material. This leads us to develop a simple method of analyzing the image contrast to give quantitative information about the thicknesses of individual layers, which cannot be obtained by any other technique. The results of this analysis for images of silicon/germanium and silicon/iron multilayers are in good agreement with the results of small-angle x-ray scattering and the readings of quartz thickness monitors during the deposition of the layers. The accuracy of the thickness measurements we obtain from transmission electron microscope images is 7% for the average layer thickness of a single component and 10% for the thickness of individual layers when the layer thickness is about 4 nm, which is comparable to the accuracy which can be attained for crystalline layers.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.347275
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  • 2
    Digitale Medien
    Digitale Medien
    Extended two-dimensional analysis of electrical breakdown between a wire and a plane (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 70 (1991), S. 4132-4138 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: The formation of a discharge between a wire and a plane has been simulated numerically through the development of large electron and positive ion number densities. When the number densities grow sufficiently large and equal a new region within the computational model is formed, within which the governing equations of the quasi-neutral region are solved for the common ion and electron number density and electric potential. Results for the temporal development of the quasi-neutral region, radial profiles of charged particle number density, electric potential, and electric field strength from discharge initiation to program termination are described. The quasi-neutral region is shown to develop first off of the discharge axis, above the wire-to-plane gap. Near the quasi-neutral region the electric field strength and electric potential are highly distorted and within the quasi-neutral region are greatly diminished.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.349135
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  • 3
    Digitale Medien
    Digitale Medien
    Tunable vacuum ultraviolet laser spectroscopy of the D(O+u) ion-pair state of jet-cooled I2 (1989)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 91 (1989), S. 7355-7360 
    Details
    ISSN: 1089-7690
    Quelle: AIP Digital Archive
    Thema: Physik , Chemie und Pharmazie
    Notizen: High-resolution vacuum ultraviolet fluorescence excitation spectra of the D(O+u) ion-pair state of I2 have been obtained using a pulsed supersonic jet. Tunable vacuum ultraviolet radiation in the region 184–200 nm was produced by Raman shifting (fifth and sixth anti-Stokes) the output from a tunable excimer pumped dye laser. Vibrational constants valid up to v'=201 in the D(O+u) state have been determined.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.457258
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  • 4
    Digitale Medien
    Digitale Medien
    Self-consistent solutions to the intersubband rate equations in quantum cascade lasers: Analysis of a GaAs/AlxGa1−xAs device (2001)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 89 (2001), S. 3084-3090 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: The carrier transition rates and subband populations for a GaAs/AlGaAs quantum cascade laser operating in the mid-infrared frequency range are calculated by solving the rate equations describing the electron densities in each subband self-consistently. These calculations are repeated for a range of temperatures from 20 to 300 K. The lifetime of the upper laser level found by this self-consistent method is then used to calculate the gain for this range of temperatures. At a temperature of 77 K, the gain of the laser is found to be 34 cm−1/(kA/cm−2), when only electron–longitudinal-optical phonon transitions are considered in the calculation. The calculated gain decreases to 19.6 cm−1/(kA/cm−2) when electron–electron transition rates are included, thus showing their importance in physical models of these devices. Further analysis shows that thermionic emission could be occurring in real devices. © 2001 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.1341216
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  • 5
    Digitale Medien
    Digitale Medien
    Carrier range and photocarrier generation efficiency on thin-film crystalline-conjugated polymers (1999)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 86 (1999), S. 1472-1476 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: The range of carriers in thin crystalline films of the conjugated polydiacetylene derivatives 3 and 4BCMU [with the side groups R1=R2=–(CH2)3–OCO–NH–CH2–COOC4H9 and –(CH2)4–OCO–NH–CH2–COOC4H9] are demonstrated to be greater than 110 and 90 μm, respectively, and the quantum efficiencies for carrier generation are determined. The films are created as a result of electron-beam-induced topochemical polymerization of a thin surface layer on a crystalline monomer substrate. The polymer films are subsequently separated from the underlying monomer and deposited onto a series of interdigitated electrodes with varying interelectrode separation. The range and generation efficiencies are deduced by measuring the photocharge induced on the electrode system as a result of a laser pulse. Comparisons are made with bulk single crystals. © 1999 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.370915
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  • 6
    Digitale Medien
    Digitale Medien
    Ion-pair formation in the photodissociation of HCl and DCl (1993)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 99 (1993), S. 4986-4992 
    Details
    ISSN: 1089-7690
    Quelle: AIP Digital Archive
    Thema: Physik , Chemie und Pharmazie
    Notizen: The vibrationally resolved excitation functions for Cl− formation from jet-cooled HCl and DCl, following photoabsorption in the region 75–86 nm (HCl/DCl+hν→H+/D++Cl−), are reported and compared with ab initio calculations. This completes our understanding of the various possible decay channels available to superexcited states of HCl and DCl that lie above the first ionization limit. Our experimental and theoretical results suggest that the Rydberg states responsible for ion-pair formation in HCl and DCl via predissociation by the V 1Σ+ ion-pair state correspond to 1Σ+ states that are only weakly autoionized. These same Rydberg states appear to act as, at least, one class of precursor states for neutral dissociation to yield excited H* and Cl* atoms.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.466000
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  • 7
    Digitale Medien
    Digitale Medien
    Measurement of intermolecular electron current in supramolecular assemblies created by the Langmuir–Blodgett technique (2000)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 87 (2000), S. 914-924 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Intermolecular photoelectron transfer in a vector ordered molecular assembly, produced as a Langmuir–Blodgett multilayer, causes currents and voltage changes at electrodes. A comprehensive account is given of the experimental determination of the voltage changes, which can be done, in principal, with a time resolution of 25 ps. The present experimental limitations to this time resolution are described. The experiments allow determination of the time evolution of the charge-separation product. The means of determining the intermolecular transfer time of the carriers in such multilayers is described. © 2000 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.371970
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  • 8
    Digitale Medien
    Digitale Medien
    Thermodynamic analysis of thermophotovoltaic efficiency and power density tradeoffs (2001)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 89 (2001), S. 3319-3327 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: This report presents an assessment of the efficiency and power density limitations of thermophotovoltaic (TPV) energy conversion systems for both ideal (radiative limited) and practical (defect-limited) systems. Thermodynamics is integrated into the unique physics of TPV conversion, and used to define the intrinsic tradeoff between power density and efficiency. The results of the analysis reveal that the selection of diode band gap sets a limit on achievable efficiency well below the traditional Carnot level. In addition it is shown that filter performance dominates diode performance in any practical TPV system and determines the optimum band gap for a given radiator temperature. It is demonstrated that for a given radiator temperature, lower band-gap diodes enable both higher efficiency and power density when spectral control limitations are included. The goal of this work is to provide a better understanding of the basic system limitations that will enable successful long-term development of TPV energy conversion technology. © 2001 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.1344580
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  • 9
    Digitale Medien
    Digitale Medien
    Deconvolution of time of flight photocurrent transients and electronic response time in columnar liquid crystals (2000)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 88 (2000), S. 918-923 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: The attempts to create thinner samples of columnar discotic liquid crystals in order to avoid stack defects and measure charge carrier motion on low defect density stacks by the time of flight technique, inevitably leads to problems. The time of flight becomes faster while the electronic response time becomes slower as a result of the increasing sample capacitance. Eventually the time of flight transit time becomes indiscernible due to the system response distortion. This article demonstrates the recovery of the time of flight signal from such distorted data by analyzing the nature of the signal and using this analysis to deconvolve a digitally acquired signal. © 2000 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.373755
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  • 10
    Digitale Medien
    Digitale Medien
    A magnetic spectrometer for intense pulsed proton beams : Proceedings of the tenth topical conference on high temperature plasma diagnostics (1995)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 66 (1995), S. 342-344 
    Details
    ISSN: 1089-7623
    Quelle: AIP Digital Archive
    Thema: Physik , Elektrotechnik, Elektronik, Nachrichtentechnik
    Notizen: A magnetic spectrometer has been constructed and used to measure energy distributions of intense proton beams in the range ∼0.3–2.5 MeV from ion diodes. Rutherford scattering foils are used to attenuate the beam before magnetic analysis. CR-39 track detectors provide time-integrated records, while an array of p-i-n diode detectors provides time-resolved data at discrete energies. The spectrometer was calibrated in the range between 0.3 and 2.0 MeV with monoenergetic protons from a Van de Graaff accelerator. The overall precision of this calibration is better than ±10 keV. Spectral measurements of intense proton beams transported in low-pressure gases are presented. © 1995 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.1146406
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