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  • 11
    Electronic Resource
    Electronic Resource
    A radial finite model of thermal lens spectrometry and the influence of sample radius upon the validity of the radial infinite model (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 73 (1993), S. 5286-5288 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Conventional thermal lens models unrealistically assume that the sample has an infinite radius. Taking realistic radial sample boundary conditions into account, a cw laser-induced mode-mismatched dual-beam thermal lens model is presented. Comparison of these two kinds of models has been made, which gives the quantitatively necessary and sufficient condition for the validity of the radial-infinite treatment on the sample: The sample radius should be larger than 2.5 times both excitation beam and probe beam radii in the sample.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.353761
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  • 12
    Electronic Resource
    Electronic Resource
    Tamm states and donors at InAs/AlSb interfaces (1995)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 77 (1995), S. 1576-1581 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Localized interface states, viz., generalized Tamm states, can be induced by an interfacial InSb bond in the InAs/AlSb heterojunction system, as confirmed by electronic structure calculations. The calculated energies of the interfacial Tamm states, however, are too low to account for the observed carrier concentrations in InAs quantum wells. Native defects capable of accounting for the observed carrier concentrations are identified, and their electronic structures calculated: AlSb in an AlSb layer is responsible for the semi-insulating character of thin InAs quantum wells and the n-type character of wide wells, and AsAl at an AlAs-like interface is responsible for the high values of electron concentration in the wells. The decrease of electron concentrations with temperature can be attributed to partial freezing of electrons into the shallow levels associated with ionized donors. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.358910
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  • 13
    Electronic Resource
    Electronic Resource
    Thermal-wave resonator cavity (1995)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 66 (1995), S. 4999-5005 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A thermal-wave resonant cavity was constructed using a thin aluminum foil wall as the intensity-modulated-laser-beam induced oscillator source opposite a pyroelectric polyvilidene fluoride wall acting as a signal transducer and cavity standing-wave-equivalent generator. It was shown that scanning the frequency of oscillation produces the fundamental and higher overtone resonant extrema albeit with increasingly attenuated amplitude—a characteristic of thermal-wave behavior. Experimentally, scanning the cavity length produced a sharp lock-in in-phase resonance with simple linewidth dependencies on oscillation (chopping) frequency and intracavity gas thermal diffusivity. The thermal diffusivity of air at 294 K was measured with three significant figure accuracy: 0.211±0.004 cm2/s. The novel resonator can be used as a high-resolution thermophysical property sensor of gaseous ambients. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1146123
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  • 14
    Electronic Resource
    Electronic Resource
    Signal generation mechanisms, intracavity-gas thermal-diffusivity temperature dependence, and absolute infrared emissivity measurements in a thermal-wave resonant cavity (1998)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 69 (1998), S. 197-203 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The operating thermal power transfer mechanisms in a thermal-wave resonant cavity were explored theoretically and experimentally. Both steady-state ac (thermal-wave) and dc temperature rise were considered, and conduction and radiation heat transfer modes were found to co-exist in the cavity. By introducing controlled variable offset dc resistive heating superposed on the fixed-amplitude thermal-wave oscillation, it was also found that the thermal-diffusivity values of the intracavity gas can vary sensitively as a function of the dc temperature rise within a thin boundary layer adjacent to the cavity thermal source (a metallic Cr–Ni alloy strip). This resulted in the measurement of the temperature dependence of the thermal diffusivity of air. Furthermore, the observed dominance of thermal-wave radiation power transfer in the phase channel of the thermal-wave signal at large cavity lengths allowed the measurement of the absolute infrared emissivity of the thin Cr–Ni strip source material: cursive-epsilon=0.091±0.004. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1148495
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  • 15
    Electronic Resource
    Electronic Resource
    Carrier transport in organic alloy light emitting diodes (2000)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 87 (2000), S. 3891-3895 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We present theoretical models and numerical results on the carrier transport mechanisms in single-layer organic alloy light emitting diodes. A typical organic alloy consists of a mixture of electron and hole transporting materials and is modeled by assigning individual conduction channels to each type of material. The sensitivity of the diode efficiency on several key parameters (alloy composition, energy level difference, contact barrier height, and traps, etc.) is studied. The results can be used to design structures to achieve balanced carrier injection and transport by properly adjusting these parameters. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.372430
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  • 16
    Electronic Resource
    Electronic Resource
    Effects of discrete trap levels on organic light emitting diodes (1999)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 85 (1999), S. 2699-2705 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have studied the effects of discrete trap levels on organic light emitting diodes under the space charge limited conditions. The interplay among the free, discrete, and exponential trap charges in single- and double-carrier devices is discussed. The sharp transitions in the current–voltage characteristics often associated with the discrete trap levels in single-carrier devices may disappear in double-carrier devices such as the organic light emitting diodes. The physics is elucidated using the energy and charge profiles. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.369587
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  • 17
    Electronic Resource
    Electronic Resource
    Thin quantum-well superlattices of GaAs and (GaAs)1−x (ZnSe)x with ZnSe: Possibility of band gaps in the blue-green (1990)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 67 (1990), S. 3761-3763 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: It is predicted that thin quantum-well superlattices or spike superlattices of GaAs in ZnSe will produce band gaps in the yellow-green, and that (GaAs)1−x(ZnSe)x spikes will lead to green and blue-green gaps. These thin quantum-well structures should have better doping properties than ZnSe for x〈0.6.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.345019
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  • 18
    Electronic Resource
    Electronic Resource
    Effects of discrete trap levels on carrier transport in organic electroluminescent devices (1998)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 83 (1998), S. 2646-2648 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The doping effect on the current–voltage characteristics of organic electroluminescent devices is studied based upon the double-carrier injection theory. The equations for the currents in the trap-charge-limited region are derived by assuming a doping-induced discrete trap level in the energy gap. Possible explanations of current experimental observations are proposed based on the equations. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.367026
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  • 19
    Electronic Resource
    Electronic Resource
    Physical mechanisms in double-carrier trap-charge limited transport processes in organic electroluminescent devices: A numerical study (1998)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 83 (1998), S. 7706-7714 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have developed a numerical model to simulate the double-carrier injection trap-charge limited (TCL) transport processes in organic electroluminescent devices (OEDs). Current–voltage characteristics, energy and charge profiles are obtained and analyzed to understand the mechanisms governing the OED performance under TCL conditions. Good agreement with general experimental trends and previous analytical predictions are achieved. Dependencies on several important parameters (carrier injection level, device thickness, recombination constant, temperature, etc.) are also studied. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.367942
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  • 20
    Electronic Resource
    Electronic Resource
    Physical Properties of Silica Aerogels Prepared with Polyethoxydisiloxanes (2000)
    Springer
    Journal of sol gel science and technology 19 (2000), S. 677-680 
    Details
    ISSN: 1573-4846
    Keywords: silica aerogel ; sol-gel ; polyethoxydisiloxanes ; supercritical drying
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Silica aerogels were made by sol-gel techniques using industrial silicon derivatives (polyethoxydisiloxanes, E-40), followed by supercritical drying with ethanol. The morphology and microstructure of the silica aerogels were investigated by using specific surface area, SBET, SEM, TEM and the pore size distribution techniques. The thermal conductivity was also measured as a function of air pressure. The results show that the diameter of the silica particles is about 13 nm and the pore size of the silica aerogels is 20–80 nm. The specific surface area of the silica aerogel is about 470 m2/g and the thermal conductivity of the silica aerogel prepared with E-40 is 0.014 w m−1 K−1 at room temperature and 1 atm.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008754504788
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