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  • 1
    Electronic Resource
    Electronic Resource
    Design of surface forces apparatus for tribology studies combined with nonlinear optical spectroscopy (1997)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 68 (1997), S. 2499-2504 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: We describe the design, calibration, and performance of surface forces apparatus with the capability of illumination of the contact interface for spectroscopic investigation using optical techniques. The apparatus can be placed in the path of a Nd-YAG laser for studies of the linear response or the second harmonic and sum-frequency generation from a material confined between the two surfaces. In addition to the standard fringes of equal chromatic order technique, which we have digitized for accurate and fast analysis, the distance of separation can be measured with a fiber-optic interferometer during spectroscopic measurements (2 Å resolution and 10 ms response time). The sample approach is accomplished through application of a motor drive, piezoelectric actuator, or electromagnetic lever deflection for variable degrees of range, sensitivity, and response time. To demonstrate the operation of the instrument, the stepwise expulsion of discrete layers of octamethylcyclotetrasiloxane from the contact is shown. Lateral forces may also be studied by using piezoelectric bimorphs to induce and direct the motion of one surface. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1148148
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  • 2
    Electronic Resource
    Electronic Resource
    Radiation effects in high-temperature thermal diffusion measurements using the laser-flash method (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 75 (1994), S. 2325-2331 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A theoretical analysis has been made to account for radiation effects in thermal diffusivity measurements at high temperatures. The analysis considers the laser-flash method based on the three-layer technique for melts. The gray-body approximation is assumed to be valid for the liquid sample which is sandwiched between two metal layers. The analysis considers radiation from the upper and lower metallic plates to the surroundings and the radiative flux due to multiple reflections between the two plates. Finite pulse time effects and the absorption of radiation in the liquid sample are also considered. The model equations have been solved numerically using a finite difference scheme. Calculations have been made for a typical liquid sample representing an oxide melt in a platinum cell assembly in the temperature interval 1273–1673 K. The effects of parameters such as sample thickness, thermal diffusivity, effective absorptivity, etc. on the temperature transient of the back surface of the lower platinum layer have been investigated. The results indicate that the radiation flux at the top surface is relatively very high initially (time(very-much-less-than)1 s). It shows a rapid decrease with respect to time and attains a small but finite value. The radiation flux from the bottom surface increases rapidly and approaches this finite value as expected. A comparison of the maximum temperature increase of the back surface of the lower platinum layer, with and without radiation correction at 1673 K, shows a typical difference of about 8%, which is quite significant. Calculations also show that liquid samples with effective absorption coefficients in the range zero to 100 m−1 can be considered to be completely transparent to radiation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.356250
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  • 3
    Electronic Resource
    Electronic Resource
    Schottky barrier heights of Pt and Ir silicides formed on Si/SiGe measured by internal photoemission (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 75 (1994), S. 5160-5164 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Lowered-barrier-height silicide Schottky diodes are desirable for obtaining longer cutoff-wave- length Si-based infrared detectors. Silicide Schottky diodes have been fabricated by the reaction of evaporated Pt and Ir films on p-Si1−xGex alloys with a thin Si capping layer. The onset of metal-SiGe reactions was controlled by the deposited metal thickness. Internal photoemission measurements were made and the barrier heights were obtained from these. Pt-SiGe and Ir-SiGe reacted diodes have barrier heights of ∼0.27 and ∼0.31 eV, respectively, higher than typical values of 0.22 and 0.12 eV for the corresponding silicide/p-Si diodes. Their emission constants are also lower and more voltage dependent than silicide/Si diodes. PtSi/Si/SiGe diodes, on the other hand, have lower barrier heights (∼0.15 eV) than the PtSi/Si barrier height. The barrier height shifts in such silicide/Si/SiGe diodes are interpreted by accounting for tunneling through the unconsumed Si layer. This is done analytically using a simple model based on the Cohen, Vilms, and Archer (unpublished) modification to the Fowler equation, and leads to an extracted barrier height, that is, the Si barrier height reduced by the Si/SiGe band offset.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.355763
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  • 4
    Electronic Resource
    Electronic Resource
    Characterization of Si/Si1−xGex/Si quantum wells by cathodoluminescence imaging and spectroscopy (1994)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 64 (1994), S. 607-609 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Cathodoluminescence (CL) imaging and spectroscopy have been used to characterize fully strained SiGe quantum wells grown on Si. At T≈5 K, the CL spectra contain only band edge luminescence features. Monochromatic imaging with the no-phonon line attributed to the bound excitons in the quantum well, has shown that the distribution of the luminescence from the wells is not uniform. The thinnest well (33 A(ring)) contained a low density of nonradiative (luminescence reduction up to 100%) spots 40–100 μm in size. The thickest well (500 A(ring)) contained similar nonradiative spots and also dark line features oriented along the 〈110〉 directions. These dark line features are areas of nonradiative recombination (up to 70%) and have been identified by transmission electron microscopy as misfit dislocations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.111064
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  • 5
    Electronic Resource
    Electronic Resource
    Room-temperature 1.3 μm electroluminescence from strained Si1−xGex/Si quantum wells (1992)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 60 (1992), S. 3177-3179 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report the first room-temperature 1.3 μm electroluminescence from strained Si1−xGex/Si quantum wells. The electroluminescence is due to band-edge carrier recombination, and its intensity increases linearly with the forward current up to 1700 A/cm2. The internal quantum efficiency is estimated to have a lower limit of 2×10−4. As the temperature is increased from 77 to 300 K, luminescence from the silicon increases relative to that from the Si1−xGex wells. A minimum band offset is required to have effective room-temperature luminescence from the Si1−xGex quantum wells.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.106734
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  • 6
    Electronic Resource
    Electronic Resource
    Photoluminescence from electron-hole plasmas confined in Si/Si1−xGex/Si quantum wells (1992)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 60 (1992), S. 1720-1722 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report the first observation of photoluminescence from electron-hole plasmas in Si/Si0.8Ge0.2/Si quantum wells. While at liquid helium temperature, luminescence due to shallow bound excitons is observed. At 77 K electron-hole plasma (EHP) luminescence dominates the spectra over a wide range of pump powers. Convolution of the occupied electron and hole densities of states gives an excellent fit to the photoluminescence line shape. A band-gap reduction of up to 15 meV at high carrier densities is observed for wide quantum wells, but no such shift is detected for narrow quantum wells.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.107196
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  • 7
    Electronic Resource
    Electronic Resource
    Symmetric Si/Si1−xGex electron resonant tunneling diodes with an anomalous temperature behavior (1993)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 62 (1993), S. 603-605 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report the fabrication of symmetric, n-type resonant tunneling diodes grown by rapid thermal chemical vapor deposition in the Si/Si1−xGex material system. Up to four resonant features were observed for both positive and negative bias. This is the first time that such highly symmetric features are reported for electron resonant tunneling in the Si/SiGe material system. A peak-to-valley ratio of 2 was achieved at a temperature of 4 K and resonances were observed up to 240 K. An additional peak is observed at low voltages exhibiting an anomalous temperature behavior, disappearing at temperatures below 50 K. Models involving phonon absorption or emitter quantization are proposed to explain this behavior.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.108869
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  • 8
    Electronic Resource
    Electronic Resource
    Quantum confinement effects in strained silicon-germanium alloy quantum wells (1992)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 60 (1992), S. 2135-2137 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report the first detailed study of quantum confinement shifts of band-edge photoluminescence energies in Si/strained Si1−xGex/Si single quantum wells. A quantum confinement energy of up to 45 meV has been observed for quantum wells as small as 33 A(ring) in width. The experimental results are in good agreement with a calculation of the hole confinement energies. The hole energy levels in quantum wells were obtained by numerically solving effective-mass equations with proper matching boundary conditions at interfaces using a 6×6 Luttinger–Kohn Hamiltonian. Both strain and spin-orbit interactions were included in the calculation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.107061
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  • 9
    Electronic Resource
    Electronic Resource
    Tunable, long-wavelength PtSi/SiGe/Si Schottky diode infrared detectors (1995)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 67 (1995), S. 506-508 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have fabricated p-type PtSi/SiGe/Si Schottky diodes with barrier heights (from photoresponse) that are lowered (relative to PtSi/Si) and highly dependent on the applied bias. The variability in the barrier height is obtained by using the SiGe/Si valence band offset as an additional barrier. When placed in close proximity to the PtSi/SiGe Schottky barrier, the total effective barrier can be altered dramatically by adjusting the applied reverse bias. The voltage sensitivity of the total barrier height can be controlled by the SiGe layer thickness. The voltage-variable barrier heights range, for example, from 0.30 eV at zero bias to 0.12 eV at 2.4 V reverse bias for a 20%, 450 A(ring) thick SiGe layer. This lowest barrier height corresponds to a cutoff wavelength of 10 μm, extending the detection range of PtSi infrared detectors to the long-wavelength range. The quantum efficiency coefficients C1 are normal at this long-wavelength end, but reduced over the rest of the tunable range, because hot carriers have to traverse the entire SiGe thickness in order to be detected. The hot carriers' energy losses from quasielastic scattering in the SiGe are taken into account in a theoretical model that gives good agreement with data. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.114551
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  • 10
    Electronic Resource
    Electronic Resource
    Technetium-99m N,N'-Bis(2-mercapto-2-methylpropyl)-2-aminobenzylamine: Technetium-99m Complexes of a Novel Bis(aminoethanethiol) Ligand (1994)
    s.l. : American Chemical Society
    Journal of medicinal chemistry 37 (1994), S. 3282-3288 
    Details
    ISSN: 1520-4804
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/jm00046a012
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