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  • 1
    Electronic Resource
    Electronic Resource
    Time-resolved temperature measurements during rapid solidification of Si-As alloys induced by pulsed-laser melting (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 73 (1993), S. 3725-3733 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The solidification of Si-As alloys induced by pulsed-laser melting was studied at regrowth velocities where the partition coefficient is close to unity. The congruent melting temperatures T0 of Si-As alloys were determined using a temperature measurement technique developed for this work, and was confirmed with T0 measurements using three other methods. The time-resolved temperature measurement uses a thin-film platinum thermistor, below and electrically isolated from the Si-As alloy layer, to directly measure the temperature during solidification. The other techniques compared the results of heat flow simulations with the fluence dependence of the peak melt depth obtained by transient conductance, the fluence dependence of the melt duration determined from time-resolved reflectivity and transient conductance, and the fluence threshold for the initiation of melting. This combination of measurements in conjunction with Rutherford backscattering spectrometry permitted the determination of the solid-liquid interface temperature, velocity and partition coefficient, the latent heat of fusion and T0 for Si-4.5 at. % As and Si-9 at. % As alloys. The values of T0 determined by all four independent methods were consistent, indicating overall agreement between the direct experimental measurements and the analyses based on heat flow simulations. T0 was determined to be 1565±25 K for 4.5 at. % As and 1425±25 K for 9 at. % As. In addition, the enthalpy of fusion was determined to be independent of composition for the range studied. The values obtained in this work are compared with previous measurements.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.352903
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  • 2
    Electronic Resource
    Electronic Resource
    Atomic force microscopy of (100), (110), and (111) homoepitaxial diamond films (1992)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 71 (1992), S. 5930-5940 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We present atomic force microscopy images of diamond films grown by chemical vapor deposition epitaxially on diamond (100), (110), and (111) substrates. The films were grown from 0.2%–1.6% mixtures of CH4 and C2H2 in H2 in a hot-filament reactor at a total pressure of 25 Torr. The substrate and filament temperatures were held at 810–1000 and 2000–2150 °C, respectively. A (100)-oriented diamond film grown with 0.3% CH4 at a substrate temperature of 810 °C was rough on the μm scale, exhibiting pyramidal features, terraces, and penetration twins, while films grown at higher substrate temperatures and hydrocarbon flow rates were smooth on the nm scale and showed evidence of a (2×1) reconstruction. A (110)-oriented film was very rough on the μm scale but nearly atomically smooth on the 0.5–5 nm scale and exhibited local slopes higher than 40° with no evidence of faceting. A film grown on a diamond (111) substrate underwent spontaneous fracture due to tensile stress and exhibited a roughness of ≈10–50 nm on the ≈100 nm lateral scale in regions far away from any cracks. The implications of the morphological features for diamond growth mechanisms are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.350443
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  • 3
    Electronic Resource
    Electronic Resource
    Remote operation of the TFTR BES experiment from an off-site location : Proceedings of the 9th topical conference on high temperature plasma diagnostics (1992)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 63 (1992), S. 4803-4805 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The capability of controlling a diagnostic subsystem and interactively participating in the experimental program on Tokamak Fusion Test Reactor (TFTR) from a remote site has been developed and demonstrated on the TFTR BES experiment. Interactive communications are established from multiscreen remote workstations at the University of Wisconsin to the Princeton Plasma Physics Laboratory VAX cluster via multiple terminal sessions across the InterNet national network. Full control of the diagnostic, access to all relevant machine parameters and wave forms, and operations run logs are all available with automatic updates between plasma shots. A real-time count-down shot clock with timer, machine event status, and shot number provides a real-time interface to the TFTR shot sequence. This means of remote participation in a central fusion experiment provides vital experience for extrapolation to implementation on an ignition device to test engineering concepts.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1143568
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  • 4
    Electronic Resource
    Electronic Resource
    Second order correction in cavity constitutive parameter measurements with application to anisotropic ferrites (1990)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 61 (1990), S. 1136-1142 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: An analysis is presented to calculate scalar permittivity and tensor permeability for ferrite materials from waveguide transmission cavity data. A correct measurement of the permittivity of ferrites and other high dielectric constant materials, requires an extension of current techniques to a second-order perturbational analysis. This second-order correction offsets an apparent frequency dependent dielectric behavior measured during a multimode cavity measurement. The analysis implies that dimensions of ferrite samples to be used in various waveguides (X-Ka bands) must be reduced to a near 0.015-in. cross-sections to eliminate a coupling of permittivity and permeability measurements.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1141961
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  • 5
    Electronic Resource
    Electronic Resource
    Comment on "Validity of the field line resonance expansion'' [Phys. Fluids B 4, 2713 (1992)] (1994)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 1 (1994), S. 1092-1094 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In a recent paper Hansen and Goertz (hereafter HG) [Phys. Fluids B 4, 2713 (1992)] considered the coupling between fast and Alfvén modes in a cold plasma containing a uniform magnetic field (B0xˆ) extending between two perfectly reflecting plane boundaries at constant x. The equilibrium medium is invariant in only one direction (yˆ), and (importantly) the density may vary along the equilibrium field lines, ρ0(x,z). HG sought solutions of the coupled governing PDEs (partial differential equations) for linear perturbations of the form exp i(kyy−ωt). The solution has been studied previously [Planet. Space Sci. 22, 483 (1974); J. Geophys. Res. 79, 1024 (1974)] in the case when ρ0 does not vary along the background field lines, when each Fourier mode in x decouples from the others and may be considered separately—reducing the problem to an ODE (ordinary differential equation). In this case a logarithmic singularity exists at the resonant field line where ω2=k2xV2A(z), VA being the Alfvén speed (V2A=B20/4πρ0). HG claim the introduction of density variation along the equilibrium field causes the modes in x to become coupled resulting in the singular ODE solution becoming a nonsingular solution in the PDE case. If this conclusion is true it is of great importance for researchers in many areas such as solar corona and laboratory plasma heating, and magnetospheric pulsations. Indeed, it suggests that a large portion of the existing literature in these fields is wrong. Clearly it is important to decide whether the calculation of HG is correct or not. In this Comment the equations they set up are analyzed and are solved in a different fashion to HG. The solution found is different from that of HG and in agreement with the existing body of literature. Some sources of error in HG's analysis are pointed out.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.870789
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  • 6
    Electronic Resource
    Electronic Resource
    YBa2Cu3O7−x-Y2O3 system and in situ deposition of trilayer heterostructures by coevaporation (1991)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 59 (1991), S. 3036-3038 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have deposited YBa2Cu3O7−x-Y2O3-YBa2Cu3O7−x heterostuctures by an in situ electron-beam coevaporation technique. Physical and chemical properties of Y2O3 were studied. The deposition conditions for Y2O3 and YBa2Cu3O7−x are completely compatible. The crystal structure of Y2O3 provides a close lattice match with YBa2Cu3O7−x and allows oxygen diffusion through Y2O3, so that heteroepitaxy and the tetragonal-orthorhombic structural transformations of YBa2Cu3O7−x can be achieved. The heterostructures are therefore of high quality. Both the top and the bottom YBa2Cu3O7−x layers are superconducting above 85 K. Tunneling phenomena on junctions fabricated from these trilayers were observed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.105785
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  • 7
    Electronic Resource
    Electronic Resource
    Metal ion dependent luminescence effects in metal tris-quinolate organic heterojunction light emitting devices (1994)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 64 (1994), S. 2718-2720 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We present a systematic analysis of the relationship between the photoluminescence (PL), light emitting device electroluminescence (EL), and conducting properties of a series of metalquinolates, Mq3, where M is a metal (Al, Ga, In, or Sc), and q3 is tris-(8-hydroxyquinoline). We compare the solution and thin film PL quantum yields and spectra of each quinolate with the EL quantum efficiencies of organic heterojunction light emitting diodes using the compound as the emitter layer. Our results indicate that, contrary to previous reports, the relative PL yield is not a good indicator of the EL quantum efficiency of a particular material. Specifically, we find that while the PL of Alq3 films is four times that of Gaq3, light emitting devices made from these two materials have comparable electroluminescence quantum efficiencies and long-term stabilities. Furthermore, the Gaq3 devices have an approximately 50% higher power efficiency than Alq3 structures, suggesting that Gaq3 is a superior emitter material for display applications.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.111453
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  • 8
    Electronic Resource
    Electronic Resource
    Absence of solute drag in solidification (1994)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 64 (1994), S. 2359-2361 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The interface response functions for alloy solidification were measured in the nondegenerate regime of partial solute trapping. We used a new technique to measure temperatures and velocities simultaneously during rapid solidification of Si-As alloys induced by pulsed laser melting. In addition, partition coefficients were determined using Rutherford backscattering. The results are in good agreement with predictions of the Continuous Growth Model without solute drag of M. J. Aziz and T. Kaplan [Acta Metall. 36, 1335 (1988)] and are inconsistent with all solute drag models.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.111614
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  • 9
    Electronic Resource
    Electronic Resource
    Nanometer-scale morphology of homoepitaxial diamond films by atomic force microscopy (1992)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 60 (1992), S. 1685-1687 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We present the first atomic force microscopy images of diamond films grown homoepitaxially in a hot filament reactor on (100), (111), and (110) natural diamond substrates. (100)-oriented diamond films grown with 0.3% CH4 at a substrate temperature of 810 °C were rough on the micron scale, exhibiting pyramidal features and penetration twins, while films grown with 1.6% CH4 at 1000 °C were nearly atomically smooth and showed evidence of a (2×1) reconstruction. A (111)-oriented film cracked due to tensile stress and was rough on the 50–500 nm scale, while a (110)-oriented film was rough on the micron scale but nearly atomically smooth on the 0.5–5 nm scale. Implications of the observed morphologies for diamond growth mechanisms are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.107237
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  • 10
    Electronic Resource
    Electronic Resource
    Reliability and degradation of organic light emitting devices (1994)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 65 (1994), S. 2922-2924 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We present a simple encapsulation technique for organic light emitting devices (OLEDs). By studying the degradation of a population of OLEDs, we show that the lifetime of encapsulated devices is increased by more than two orders of magnitude over that of unencapsulated devices. In both cases, degradation is primarily due to the formation of nonemissive regions, or dark spot defects. By studying the structure and evolution of the dark spots, we infer that the growth of electrode defects limits device lifetime. Hermetic packaging of OLEDs is essential if they are to be used in commercially viable flat panel displays. © 1994 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.112532
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