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  • 1
    Electronic Resource
    Electronic Resource
    Effects of Penning reactions and excitation rate on the pulsed transverse-discharge neon laser for photodynamic therapy (1995)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 78 (1995), S. 30-38 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Theoretical analysis of the output performance of a transverse discharge pumped neon Penning laser (585.3 nm) using a mixture of Ne/H2 is described. The validity of the kinetic model is confirmed by comparing the results to the experimental discharge and laser performance. It is theoretically shown that the optimum mixing ratio of the Ne/H2 mixture is 1:2.5, and the optimum operating pressure is about 56 Torr. The model also predicts that the intrinsic efficiency reaches a peak of 8.5×10−6 at an excitation rate of 0.5 MW/cm3 under the optimum mixing ratio and operating pressure conditions. At excitation rates in excess of 0.5 MW/cm3 the laser output power is slowly increasing and then saturates due to electron collisional quenching of the upper laser level. The laser power extraction is increased by laser injection seeding in order to rapidly build up the lasing. The improved intrinsic efficiency is about two times higher than without the injection seeding. The improved specific laser output is 8 W/cm3, therefore, a discharge volume of 125 cm3 will be able to generate the peak laser power reaching 1 kW. This power value is sufficient to obtain the same treatment effect as the gold vapor laser used in photodynamic therapy. Moreover, by fitting this model to the experimental results of the laser output energy with a Ne/D2 mixture, it is shown that the Penning ionization rate constant of H2 is larger than that of D2. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.360677
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  • 2
    Electronic Resource
    Electronic Resource
    Adhesion and deformation of metal/polyimide layered structures (1989)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 65 (1989), S. 1911-1917 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Adhesion and interfacial failure of Cr, Cu, and Cu/Cr films on a thin pyromellitic dianhydride-oxydianiline polyimide substrate have been investigated using a recently developed stretch deformation technique. This method directly measures the energy required to separate the interface from the difference in the load versus elongation curves between film/substrate and substrate structures. The failure mode was observed in combination with morphological studies by in situ optical microscopy and scanning and transmission electron microscopies. The stress distribution in the sample upon stretching has been computed by a finite element analysis. The difference in the stress relief modes, film fracture, and delamination behavior for Cu versus Cr films is discussed. The important role of crack formation in the metal overlayer for initiating failure is demonstrated. The effects due to the addition of a brittle Cr interface layer between polyimide and Cu on the buildup of stress and the onset of failure have also been investigated.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.342903
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  • 3
    Electronic Resource
    Electronic Resource
    Cryogenic scanning tunneling microscope for quantum dot spectroscopy (2001)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 72 (2001), S. 2989-2995 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: We have designed and fabricated a cryogenic scanning tunneling microscope for probing lithography defined nanometer-scale devices. The piezoelectric double tube is capable of scanning an area up to 22 μm×22 μm, while maintaining atomic resolution. In addition, the sample mount has a 5 mm×4 mm traveling range. Most importantly, the system is compact and, as a result, it can be inserted into the bore of a superconducting magnet. In this work, we demonstrate a unique application of scanning tunneling system, i.e., the scanning tip is in direct contact with the sample. The spectroscopic information therefore reflects the true characteristics of the devices under test, unlike the typical case where the tunneling barrier through vacuum imposes a large series resistance, on the order of 109 Ω. The design as well as the operation of this compact scanning tunneling microscope is described. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1379608
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  • 4
    Electronic Resource
    Electronic Resource
    Nanometer-size InAs/AlSb quantum wires: Fabrication and characterization of Aharonov–Bohm quantum rings (2000)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 88 (2000), S. 5272-5276 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report a fabrication method for laterally confining the two-dimensional electrons in InAs/AlSb single quantum wells into artificially patterned conducting wires. The minimum wire width is demonstrated to be ∼30 nm, among the smallest reported to date. The confining potential is approximately square and abrupt, and that makes the electron's spatial distribution in the transverse direction the same as the physical width of the wire. The conducting electrons have close proximity to the surface charges, thus there is always a reduction in the elastic mean free path when the wire width decreases. Despite the reduction in mean free path, we find that the phase coherence length is approximately 1 μm at 2.2 K, a factor of 30 larger than the minimum feature size. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1316053
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  • 5
    Electronic Resource
    Electronic Resource
    The I-V characteristics of double-barrier resonant tunneling diodes: Observation and calculation on their temperature dependence and asymmetry (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 70 (1991), S. 3131-3136 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report a calculation on the current-voltage characteristics of double-barrier resonant tunneling diodes. The results can well-explain experimental observations, in particular, the temperature dependence of both the absolute current amplitude and the resonant voltage positions. Our calculation takes into account the self-consistent Poisson equation, quantum mechanical tunneling, and band-gap offset at the heterojunctions. In addition, the calculation includes a realistic scattering-induced broadening effect, with which a quantitative fit throughout the entire negative differential resistance (NDR) region is demonstrated. Finally, we show that the differential resistance in the NDR region can be tuned, when asymmetrical tunneling barriers are used.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.349292
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  • 6
    Electronic Resource
    Electronic Resource
    Output characteristics of a discharge-pumped F2 laser (157 nm) with an injection-seeded unstable resonator (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 2241-2246 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: To improve beam quality, an injection-seeded unstable resonator was applied to a discharge-pumped F2 laser, which is normally dominated by amplified spontaneous emission with a large beam divergence when using a normal stable cavity, due to the laser's extremely high gain (a small-signal gain-length product ∼29). The time-dependent injection-seeding efficiency was obtained for various injection timings by measuring a ratio of the output laser intensity with the same polarization as the seed laser. Correlation of the injection-seeding efficiency with the temporal evolution of the laser-beam divergence was also studied. Both the time-dependent beam divergence and the injection-seeding efficiency showed degradation at a later part of the laser pulse.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.354706
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  • 7
    Electronic Resource
    Electronic Resource
    Electronic properties of silicon δ-doped InSb (1992)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 72 (1992), S. 671-675 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have investigated magneto-transport and cyclotron resonance (CR) of two-dimensional electron gas in silicon δ-doped p-InSb under a magnetic field of up to 12 T at 4.2 K. Because there are multiple subbands occupied, Shubnikov–de Haas oscillations show a beating behavior. The CR spectra also display several peaks originating from different subbands. Effective masses of electrons associated with the lowest three subbands can therefore be directly determined, and they are in excellent agreement with a self-consistent calculation, which takes into account the electrostatic Poisson equation, the Schrödinger equation, and realistic sample parameters. Furthermore, we observed an absorption peak, whose resonance position has anomalous angle dependence. It is attributed to impurity CR where donors are in the vicinity of the δ-doped sheet.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.351850
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  • 8
    Electronic Resource
    Electronic Resource
    Quantum mechanical correction on capacitance-voltage characteristics of narrow gap semiconductors (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 70 (1991), S. 2208-2210 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We show that for narrow band-gap semiconductors, the doping concentration deduced from capacitance-voltage measurements can be substantially underestimated due to surface quantization effect. While our derivation can be applied to all materials, detailed accounts on p-type Hg0.788Cd0.212Te are given as an example. We found that for a practical doping range, 1×1015 cm−3 to 1×1017 cm−3, the doping level can be underestimated by 53% to 173%, respectively.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.349460
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  • 9
    Electronic Resource
    Electronic Resource
    On the intrinsic bistability in resonant tunneling structures: Observation of area and temperature dependence of hysteresis (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 70 (1991), S. 2473-2475 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report experimental observation on the area and temperature dependence of the hysteresis in the current-voltage characteristics of double-barrier resonant tunneling diodes. Our observation shows that the hysteresis can simply result from a load line effect, since (1) the hysteresis will disappear when the the device area is reduced, and (2) the hysteresis becomes wider at lower temperatures. We compare the data with theoretical predictions from the intrinsic bistability picture, and obtain the criterion for observing current bistability.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.349404
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  • 10
    Electronic Resource
    Electronic Resource
    Modeling of a new field-effect resonant tunneling transistor (1992)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 71 (1992), S. 1537-1539 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We present quantum mechanical self-consistent calculations on the transfer characteristics of a new resonant tunneling transistor. The model structure consists of a source, a tunneling barrier, a quantum-well drain, a thick insulator, and a backgate. The tunneling barrier consists of a double-barrier structure. We demonstrate that based on energy and momentum conservations, the transistors display oscillatory negative transconductance, as the gate can control the resonant tunneling probability between source and drain. With the inclusion of a realistic energy relaxation time of ∼0.1 ps, the double-barrier resonant tunneling transistor shows an enhancement of the tunneling current density and the negative transconductance feature is only slightly changed. We also find that the quantum-well drain is not able to completely screen the electric field imposed by the backgate bias as a result of limited density of states of two-dimensional systems.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.351226
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