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Applied Physics Letters

Issue 9 • Date Nov 1974

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Displaying Results 1 - 25 of 25
  • Issue Table of Contents

    Page(s): toc1
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    Freely Available from IEEE
  • Effect of bias field in a zinc‐oxide‐on‐silicon acoustic convolver

    Page(s): 473 - 475
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    A monolithic acoustic surface wave parametric signal processor, fabricated with sputtered zinc oxide on an oxidized epitaxial n ‐on‐n+ silicon substrate, is demonstrated. The dependence of the convolution output signal strength on applied gate bias is analyzed, and it is found that the maximum output occurs just before the semiconductor surface inverts, at which time the high‐frequency capacitance‐voltage characteristic has its maximum slope. View full abstract»

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  • Efficient acousto‐optic TE⇄TM mode conversion in ZnO films

    Page(s): 476 - 477
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    The TE⇄TM mode conversion by acoustic surface waves in a ZnO‐film optical waveguide fabricated on a fused‐quartz substrate is described. An efficient mode conversion as high as 88% has been accomplished in a waveguide with a film thickness of 5 μm at an acoustic frequency of 226 MHz and an acoustic power of 350 mW. View full abstract»

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  • Monolithic acoustic imaging transducer structures with high spatial resolution

    Page(s): 478 - 479
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    A method is described for simplifying the construction of high‐resolution imaging transducers by using impedance matching transformers on a monolithic plate structure. Simple physical arguments are used to establish the general design criterion that a broad frequency response leads to a wide angular response and high resolution. This conclusion is verified by numerically computed performance curves for a particular air‐backed transducer structure. View full abstract»

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  • Alignment of nematics and smectics on evaporated films

    Page(s): 479 - 481
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    We discuss the alignment of nematics and smectics on substrates where an obliquely evaporated thin film has been previously deposited. In the planar samples, the surface anchoring energy is substantially larger than with the traditional rubbing technique. We can also uniformly align the liquid crystals obliquely, in particular by coating the evaporated film by a surfactant. View full abstract»

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  • GaAs transmission photocathode grown by hybrid epitaxy

    Page(s): 482 - 483
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    Transmission GaAs/GaAlAs/GaP photocathodes have been grown by a combination of LPE and VPE (hybrid) epitaxy. The quality of the VPE GaAs material is comparable to that grown by LPE, and the surface uniformity and quality is comparable to that generally obtained by VPE. The GaAs/GaAlAs heterojunction is characterized by low interface recombination velocity. View full abstract»

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  • Filamentation of intense relativistic electron beams propagating in dense plasmas

    Page(s): 484 - 486
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    It is observed that relativistic electron beams propagating in magnetized dense plasmas (np≫nb) split into filaments at low values of magnetic field. The beam filamentation is inhibited at higher values of magnetic field, but is affected only slightly with increasing beam ``temperature''. The instability is accompanied by intense microwave emission, the power of which increases exponentially with magnetic field. View full abstract»

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  • GaAsGa1-xAlxAs double‐heterostructure distributed‐feedback diode lasers

    Page(s): 487 - 488
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    We report laser oscillation at 80–100°K in electrically pumped GaAsGa1-xAlxAs double‐heterostructure distributed‐feedback diode lasers. The feedback for laser oscillation was provided by a corrugated interface between the active GaAs layer and the p‐Ga1-xAlxAs layer. The lowest threshold current density was 2.5 kA/cm2 in pulsed operation. The wavelength of laser emission was 8112 Å at 82°K with a half‐width of less than 0.3 Å. The temperature dependence of the laser wavelength was found to be smaller than that of the conventional Fabry‐Perot laser. View full abstract»

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  • Green electroluminescence in crystals of ZnS0.6Se0.4

    Page(s): 489 - 491
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    Green‐light‐emitting devices with electrode areas of 1 mm2 have been prepared on crystals of a solid solution of zinc sulfide and selenide with the composition ZnS0.6Se0.4. A luminance of 200 fL was achieved at a bias of 11 V which corresponds to a power efficiency of 0.06%. The emission at room temperature was contained in a braod band with a maximum at 5450 Å (2.27 eV). Preliminary trials with a crystal of zinc sulfide produced a blue (4800 Å, 2.58 eV) emission with a luminance of 90 fL from an area of 1 mm2 for a power dissipation of 600 mW at a bias of 20 V. View full abstract»

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  • Tunable spin‐flip Raman scattering in mercury cadmium telluride

    Page(s): 491 - 493
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    Tunable spin‐flip Raman scattering has been observed in Hg0.766Cd0.234Te using several CO2 laser lines near 9.5 μm to pump the crystal. The Stokes component with a maximum power output of about 1 W was tunable between 15 and 68 cm-1 from the pump frequency with magnetic fields between 4 and 21 kG. This corresponds to an average tuning rate of 3.4 cm-1/kG. The extrapolated zero‐field g factor was measured to be |79|±3 yielding a conduction band‐edge effective mass ratio of 0.0101±0.0005. Several factors suggest that the tunable radiation was stimulated. View full abstract»

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  • Enhanced optical frequency detection with negative differential resistance in metal‐barrier‐metal point‐contact diodes

    Page(s): 493 - 495
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    Enhanced optically induced voltages have been observed across the junction of metal‐barrier‐metal point‐contact diodes which exhibit a current‐controlled negative differential resistance. Responsivities in excess of 5 V/W have been demonstrated when the incident optical beam is focused to ∼1 W/cm2 at the junction. This enhancement is in agreement with the behavior expected from the rectification of the optical field. View full abstract»

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  • cw harmonic generation in the uv using a thin‐film waveguide on a nonlinear substrate

    Page(s): 495 - 498
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    Phase‐matched second harmonic in the thin‐film and nonlinear Cerenkov radiation in the substrate have both been observed in the uv on a cw basis in a thin‐film waveguide structure consisting of an aluminium‐oxide film deposited on a quartz substrate. A sharp resonance in the second‐harmonic output was observed as the fundamental wavelength was tuned through the phase‐matching point. In contrast, the Cerenkov radiation was found to be broadly and continuously tunable and relatively intense. View full abstract»

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  • Continuously tunable xenon laser at 1720 Å

    Page(s): 498 - 500
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    We report the first continuously tunable vacuum ultraviolet laser emission in high‐pressure xenon. By incorporating a dispersive element into the optical cavity, laser action was obtained over a 50‐Å (1700‐cm-1) range about a central wavelength of 1720 Å. A highly efficient pumping scheme allows the use of a 0.6‐MeV electron accelerator delivering ≤ 10 J in a 3‐nsec excitation pulse. View full abstract»

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  • Laser propagation through an absorbing transonic flow

    Page(s): 500 - 503
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    Experiments were carried out to investigate the propagation of a cw CO2 laser beam through an absorbing slightly supersonic flow. A 500‐W CO2 beam was propagated through a small blow‐down wind tunnel operating with an air/SF6 mixture in order to simulate a high‐power beam propagating through the atmosphere. A collinear schlieren system was used to observe the density gradients caused by the absorbed power. Large density gradients were observed at a Mach number of 1.17; however, they were not shock initiated and their magnitude was not inconsistent with a heat‐balance analysis. Under the conditions of the experiment no shock waves were observed, even though their occurrence was predicted by a simple one‐dimensional analysis. From this study it is concluded that shock waves will not occur under most conditions encountered by high‐power cw CO2 laser radiation in the atmosphere. The presence of subshock density gradients and their effect on the propagating beam require further study. View full abstract»

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  • Determination of bulk‐trap parameters in MIS structures

    Page(s): 503 - 505
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    A new nonsteady‐state thermal technique for determining the parameters of traps through which electron‐hole pairs are generated in the depletion layer of the silicon in metal‐insulator‐silicon (MIS) structures has been applied to metal‐nitride‐oxide‐silicon (MNOS) structures. The trapping level involved in the generation process was found to be at 0.55 eV and the carrier lifetime was approximately 3 μsec. View full abstract»

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  • The effect of arsenic in improving lifetime in silicon‐on‐sapphire films

    Page(s): 505 - 506
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    Earlier workers reported a considerable increase in the lifetime of phosphorus‐doped n ‐on‐n+ silicon‐on‐sapphire (SOS) films. We report in this paper that a similar improvement in lifetime is obtained on arsenic‐doped SOS film comprised of a higher‐resistivity layer on top of a nondegenerate lower‐resistivity layer. The significance of this work lies in that (a) from the device fabrication point of view arsenic is preferable because of its lower diffusion constant, and therefore will not out‐diffuse during subsequent processing steps; and (b) a nondegenerate lower layer is sufficient to produce an improvement in lifetime. It is also shown that the generation lifetime τg increases exponentially with distance from the Al2O3Si interface. View full abstract»

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  • Determination of intervalley electron‐phonon deformation potential constants in n ‐silicon by analysis of high electric field transport properties

    Page(s): 507 - 509
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    The intervalley electron‐phonon deformation potential constants in n ‐silicon were determined by fitting the theoretical high electric field transport properties (established using an ``exact'' solution to the Boltzmann transport equation) to those obtained experimentally at 77 K. The principal contribution to intervalley scattering under warm and hot electron conditions was found to come from a 680 K f ‐type phonon (Df=6.85×108 eV/cm for coupling to one other valley) with much weaker contributions from 210 K (Dg =0.7×108 eV/cm) and 130 K (Dg =0.6×108 eV/cm) low‐energy g ‐type phonons. Good agreement was also obtained between the experimentally and theoretically determined repopulation versus field. View full abstract»

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  • Bistable switching on gallium arsenide Schottky gate field‐effect transistors

    Page(s): 510 - 511
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    A bistable switching phenomenon including a memory effect has been observed on a GaAs FET with Schottky gate. The characteristics of the two states of the transistor appear to be very different, the first having a high input impedance of the gate and the second Ohmic behavior of the gate. Transitions between these two states are achieved through negative or positive pulses applied to the gate. The transition time is less than 1 μsec. Each state remains stable over a period of weeks. View full abstract»

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  • Surface state band on GaAs (110) face

    Page(s): 511 - 514
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    Careful photoemission studies of surface states on the cleavage GaAs (110) detect no filled states in the band gap. However, empty states pin the surface Fermi level on n ‐type GaAs at midband gap. Filled states are placed below the valence‐band maximum and empty surface states in the upper half of the band gap. Calculations, using the bond orbital model, agree with these results and associate the empty and filled bands with Ga and As, respectively. View full abstract»

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  • Temporally coincident ultrashort pulses from synchronously pumped tunable dye lasers

    Page(s): 514 - 516
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    The temporal and spectral character of the picosecond pulses from a dye laser which was synchronously pumped by a frequency‐doubled mode‐locked Nd:glass laser was studied with an ultrafast streak camera. For matched pump and dye laser cavity lengths, the observed dye pulses were of 15‐psec duration and were in very close temporal synchronism with the pump pulses. For deviations from match ≫0.1 mm, severe aberrations in pulse character began to occur. Spectral tuning of the dye laser was achieved with a narrow‐gap etalon. The utility of such lasers in producing two independently tunable time‐synchronized ultrashort pulses for parametric frequency generation and spectroscopic studies is discussed. View full abstract»

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  • High‐pressure CS2 electric discharge laser

    Page(s): 517 - 520
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    Laser action has been observed at 11.5 and 12.2 μm in electron‐beam‐stabilized electric discharges using He/CO/CS2 and He/N2/CS2 gas mixtures. Laser operation at 1 atm pressure was possible using He/CO/CS2 mixtures. Laser assignments, aided by the use of 13C‐enriched samples, indicate that the 001 to 100 and 0111 to 1110 transitions of CS2 both contribute to the lines observed. Line coincidences, which are very likely for several bands of CS2, may be the cause of the anomalous laser intensity distribution among the rotational states observed at low pressures. View full abstract»

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  • A 1.4–4‐μm high‐energy angle‐tuned LiNbO3 parametric oscillator

    Page(s): 520 - 522
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    We have operated a high‐gain angle‐tuned singly resonant LiNbO3 parametric oscillator pumped directly at 1.06 μm by a Q ‐switched Nd:YAG laser. The oscillator angle tunes from degeneracy and operates over the entire 1.4–4.4‐μm range. Output energies of greater than 1 mJ/pulse at 5 pps have been observed with a 15% energy conversion efficiency. The key to this device is the large LiNbO3 crystals fabricated from new [01.4] grown boules. Crystals up to 15 mm in diameter and 5 cm in length have been cut at the nominal 47° orientation. These crystals will potentially handle over 2 J of optical energy at 1.06 μm. View full abstract»

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  • Junction edge region thermally stimulated capacitance (TSCAP) of n ‐Si doped with phosphorus and bismuth

    Page(s): 523 - 524
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    The high‐temperature (T≫77°K) thermally stimulated capacitance (TSCAP) from the ionization of impurity centers located in the edge region of a semiconductor (Si) junction doped with two shallow level impurities (P and Bi) where one is the ``deep'' level trap (Bi) is reported for the first time. The theoretically predicted reverse bias voltage dependence of the size of the TSCAP is also verified experimentally. View full abstract»

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  • The electrical effect on Schottky barrier diodes of Si crystallization from AlSi metal films

    Page(s): 524 - 526
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    The barrier height of n‐Si Schottky contacts made with Si‐doped Al metallization is observed to vary from 0.79±0.02 V to 0.89±0.02 V after heat treatments at temperatures from 400 to 550°C. Identical diodes made with pure Al metallization have φB =0.68±0.02 V. The scanning electron microscope in the electron‐beam‐induced‐current mode is used to show that the upward shift in φB is due to a thin layer of p ‐doped Si, probably continuous, which is grown from the AlSi metallization on the n contacts. The discretely distributed Si mesas and precipitates reported by other investigators as crystallizing out of the metallization are observed also, but are believed to play a limited electrical role. View full abstract»

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  • Quantum interference effects in high‐transition‐temperature thin‐film materials

    Page(s): 527 - 528
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    Superconducting quantum interferometers with operating temperatures of up to 17°K have been fabricated from thin films of Nb3Sn and NbN by means of photolithographic and argon ion etching techniques. View full abstract»

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Applied Physics Letters, published by the American Institute of Physics, features concise, up-to-date reports on significant new findings in applied physics.

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Nghi Q. Lam
Argonne National Laboratory