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Applied Physics Letters

Issue 10 • Date Nov 1977

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Displaying Results 1 - 25 of 35
  • Issue Table of Contents

    Page(s): toc1
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    Freely Available from IEEE
  • A monolithic zinc‐oxide–on–silicon p‐n‐diode storage correlator

    Page(s): 641 - 643
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    A monolithic zinc‐oxide–on–silicon p‐n storage correlator has been constructed. When operated both as a convolver and as a storage correlator, the electronic efficiency obtained with this device is comparable to that of the present LiNbO3 airgap devices. This device has the potential of having very large dynamic range because of the absence of spurious bulk‐wave generation, as occurs in the airgap device. Several signal‐processing functions have been demonstrated with this new type of storage correlator. In one chirp correlation experiment, correlation of signals with a time‐bandwith product of 4000 has been observed. View full abstract»

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  • Actively controlled SAW power divider

    Page(s): 643 - 645
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    The operation and construction of a new actively controlled SAW power divider is presented. The amount of power delivered to either of two outputs can be controlled with a voltage less than +30 V. The two essential components of this device are a SAW magic tee fabricated on yz LiNbO3 and an acoustoelectric phase shifter which uses silicon air‐gap coupled to the LiNbO3. View full abstract»

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  • Laser fusion ion temperatures determined by neutron time‐of‐flight techniques

    Page(s): 645 - 647
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    Measurements have been made of the energy spectrum of neutrons emitted as a result of laser compression of D‐T‐filled glass microshells using a time‐of‐flight spectrometer. From the width of unfolded energy spectra, plasma ion temperatures of approximately 6 keV have been determined for 90‐μm‐diam targets irradiated with 2 TW of 1.06‐μm light. The measured mean neutron energy of 14.00±0.10 MeV agrees with the expected value of 14.05 MeV. View full abstract»

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  • Photoionization of He and N2 by uv radiation from a copper plasma produced by a CO2 laser

    Page(s): 647 - 649
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    Measurements of the attenuation in a background gas, He or N2, of the uv radiation produced by a 1.7‐ns 4‐J CO2 laser irradiation of a copper target are reported. Photoionization cross sections of 0.4 Mb in He and 0.9 Mb in N2 are obtained. The photoionizing radiation is attributed to the 110.6‐Å M1 transition in copper. View full abstract»

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  • Ion implantation distributions in inhomogeneous materials

    Page(s): 649 - 651
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    The integral equation for ion‐implantation range, damage, and ionization distributions in random media is generalized to allow nonuniform target materials. The generalization range equation is solved in the path‐length approximation, using power‐law cross sections, for a target consisting of two dissimilar half‐spaces. There is a discontinuity in the distribution at the interface, proportional to the value of the distribution in the material the projectile is leaving; the constant of proportionality is evaluated explicitly. View full abstract»

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  • Determination of concentrations of donors and acceptors in GaAs by an optical method

    Page(s): 652 - 654
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    The concentrations of donors (ND) and acceptors (NA) in a high‐quality GaAs epitaxial layer sample are determined by the optical method. The numerical values of ND and NA are deduced from the limiting values of combinations of the excitation‐dependent integrated emission intensities due to the conduction‐band–to–neutral‐acceptor, neutral‐donor–to–valence‐band, and neutral‐donor–to–neutral‐acceptor transitions. View full abstract»

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  • Frost suppression in photoconductor‐thermoplastic holographic recording devices

    Page(s): 654 - 656
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    Our findings indicate that the frost‐formation phenomenon common to many photoconductor‐thermoplastic devices can be attributed to spinodal decomposition processes. This decomposition is induced by the inherent electrical field of about 106 V/cm in the plasticized and polydispersed thermoplastic melts. By using monocomponent polystyrene of sharply defined molecular weight distribution for the thermoplastic layer the frost formation is suppressed, so that holograms having high signal‐to‐noise ratio can be readily recorded. View full abstract»

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  • Generation of near‐infrared picosecond pulses by mode‐locked synchronous pumping of a jet‐stream dye laser

    Page(s): 657 - 658
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    Picosecond pulses continuously tunable from 685 to over 900 nm have been obtained from a dye laser synchronously pumped by a mode‐locked krypton laser. The pulse duration was measured by autocorrelation techniques to be as short as 25 ps. Conversion efficiency up to 30% and average power in excess of 400 mW were observed. Continuous‐wave laser operation for three new dyes between 870 and 985 nm is also reported. View full abstract»

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  • Near‐atmospheric‐pressure xenon excimer laser

    Page(s): 659 - 661
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    Oscillation at 172 nm for 200 nsec has been observed at a pressure of 1.5 atm of xenon with a 1‐m length of gain medium pumped by a 200‐kV 7‐A/cm2 1‐μsec electron beam. The observed behavior agrees with calculations based on the excited‐state mixing model for this new operating regime. The results support model predictions that a modest increase in excitation rate (about a factor of 2) would yield quasi‐steady‐state laser oscillation with an intrinsic efficiency near 5%, a fluence of ∼1 J/cm2, and a peak intracavity two‐way flux of ∼50 MW/cm2. In optimized laser amplifier designs, significantly higher amplifier efficiencies should be possible. View full abstract»

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  • Coherent uv from a TEA N2 laser system

    Page(s): 661 - 663
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    A technique is described to couple and synchronize two transversely excited atmospheric (TEA) nitrogen lasers in an oscillator‐amplifier configuration to obtain spatially coherent 1‐nsec pulses at 337 nm with an energy/pulse of several hundred microjoules. The technique should be adaptable to other very high gain laser systems whose operation terminates so quickly as to render optical resonators impractical. View full abstract»

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  • High‐speed holography of laser‐induced breakdown in liquids

    Page(s): 663 - 664
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    The phenomenon of ruby laser‐induced breakdown in liquids is investigated by high‐speed holography. The advantage of using holography instead of ordinary photography lies in the possibility to easily suppress the bright white light emitted during the breakdown process. This light constitutes an incoherent background on the holographic plate and does not reproduce upon reconstruction of the recorded scene. View full abstract»

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  • Selective absorption of solar energy in ultrafine chromium particles

    Page(s): 665 - 666
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    Ultrafine chromium particles prepared by evaporation in argon + air are found to be highly absorbing over the solar spectrum and highly transparent in the infrared. Such spectral selectivity is the distinctive feature of a coating in an efficient photothermal converter for solar energy. Optical transmittance through coatings with mass density ≲0.5 g/m2 agrees well with calculations based on the Maxwell‐Garnett theory, whereas coatings with larger mass density exhibit a transmittance too low to be directly reconciled with this theory. View full abstract»

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  • Barrier tunneling as a possible efficient pump for exciplex gas lasers

    Page(s): 667 - 669
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    It is suggested that quantum‐mechanical tunneling might be used in some instances to provide efficient two‐body collision formation of quasibound molecular states suitable for exciplex laser systems. Some evidence for the existence of the necessary bumps in the molecular potential curves is discussed, and it is noted that potential bumps of the general magnitude and width required are apt to be produced whenever an appreciable cross section exists for endothermic excitation transfer from a metastable state of one gas to an excited state of another gas. View full abstract»

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  • Power enhancement of continuous ultraviolet lasers

    Page(s): 670 - 672
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    High‐power cw laser radiation from nine Ar and five Kr laser transitions in the spectral range 275 ≪λ≪365 nm has been generated in a highly ionized low‐pressure dc discharge. The output increases without saturation up to the maximum available discharge current of 480 Å. The most intense emission is 61 W obtained from the combined 351.1‐ and 363.8‐nm Ar III lines. View full abstract»

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  • Theoretical absorption spectra for Ne+2, Ar+2, Kr+2, and Xe+2 in the near ultraviolet

    Page(s): 672 - 674
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    Near‐ultraviolet absorption spectra for the I(1/2)u→II(1/2)g transition have been calculated for Ne+2, Ar+2, Kr+2, and Xe+2 using ab initio configuration interaction methods. The spectra are all similar except that the position of maximum absorption shifts to longer wavelength for the heavier rare gases. The absorption cross sections are tabulated at the wavelengths of the KrF, XeBr, XeCl, and XeF lasers. View full abstract»

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  • Fiber‐optical relay

    Page(s): 675 - 676
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    Metallic pads on optical fibers are heated by the absorption of light at the 1‐μW–10‐mW power level. Due to differential thermal expansion, the fibers bend, and, by misaligned coupling, modulate guided light signals. An optically operated relay, a narrow‐band audio‐frequency resonator, and a self‐commutating optically powered oscillator are demonstrated. View full abstract»

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  • Injection locking of a xenon fluoride laser

    Page(s): 677 - 679
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    Operation of a XeF laser at high spectral power densities on transitions within a single vibrational band has been demonstrated. An electron‐beam‐controlled discharge XeF laser was operated as an injection‐locked regenerative amplifier. A narrow‐band signal from an étalon‐tuned XeF laser was used to lock the regenerative amplifier. Competition between the various components of the emission spectrum was observed. Homogeneous extraction is observed within each vibrational band, indicating that the rotational cross‐relaxation time is substantially faster than the radiative lifetime of XeF. Coupling between vibrational bands was not observed. These measurements indicate that the efficient extraction from XeF on a single rotational transition should be possible. The band at 351 nm was found to consist of components arising from at least two different vibrational bands. The transitions in the 353‐nm band and one component of the 351‐nm band share a common vibrational level in the upper electronic state. These observations are consistent with current vibrational assignments of the XeF spectrum. View full abstract»

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  • Use of electron‐trapping region to reduce leakage currents and improve breakdown characteristics of MOS structures

    Page(s): 680 - 682
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    A trapping layer of W (≈1014 atoms/cm2) has been deposited between 70 Å of thermal silicon dioxide grown from a polycrystalline silicon substrate and 520 Å of deposited pyrolytic silicon dioxide in an MOS structure to reduce high leakage currents and low‐voltage breakdowns associated with asperities at the polycrystalline Si–thermal SiO2 interface. MOS structures without the W layer but with the pyrolytic SiO2 layer were also found to be effective. This improvement is ascertained to be due to localized electron trapping in the W or pyrolytic oxide layer at low average fields which reduces the locally high fields and therefore high dark currents associated with the asperities. At higher average fields uniform trapping is believed to be dominant. This uniform effect can also enhance the breakdown characteristics if the trapped charge is not detrapped by the applied field. View full abstract»

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  • A search for interface states in an LPE GaAs/AlxGa1-xAs heterojunction

    Page(s): 683 - 684
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    We have used the DLTS capacitance spectroscopy technique to search for interface states associated with an LPE GaAs/Al0.22Ga0.78As heterojunction. The results can be interpreted in terms of well‐known deep bulk states shifting abruptly at the interface with no observable interface states. The limiting values are ≪5×108 and ≪4×109 cm-2 interface states (deeper than 0.1 eV) in the upper and lower half of the gap, respectively. View full abstract»

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  • Hall‐effect determination of the N‐trap bound state in GaAs1-xPx

    Page(s): 685 - 687
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    Hall‐effect measurements as a function of temperature on nitrogen‐containing GaAs1-xPx have shown that the nitrogen isoelectronic trap in these materials can be best described by a bound state in the band gap, occupied by electrons according to the equilibrium thermal distribution. It is shown that the presence of nitrogen can have a pronounced effect on the free‐carrier density. Our results are in excellent agreement with recent optical data. View full abstract»

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  • Tunnel triode—a tunneling base transistor

    Page(s): 687 - 689
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    Proposed is a triode structure made of semiconductor heterojunctions where carriers of one type tunnel through the base region to which carriers of the other type are confined. In1-xGaxAs and GaSb1-yAsy alloys are candidates for this heterostructure. As a three‐terminal amplifier, the device is expected to exhibit high impedances for both input and output, a large current gain, and a marked improvement in high‐frequency peformance. View full abstract»

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  • Silicon epitaxy by solid‐phase crystallization of deposited amorphous films

    Page(s): 689 - 691
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    We report the solid‐phase growth of epitaxial Si thin films by the heating of amorphous Si deposited onto atomically clean (100) Si substrates at room temperature. Epitaxial Si layers ranging in thickness from 1000 to 5000 Å have been grown by heating the amorphous films in ultrahigh vacuum to temperatures of 500–600 °C. Good crystal quality of the layers grown by this method has been demonstrated by Rutherford backscattering and transmission electron microscopy. View full abstract»

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  • Application of Monte Carlo calculation to fundamentals of scanning Auger electron microscopy

    Page(s): 692 - 694
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    Spatial distributions of Auger signals generated in an aluminum target in scanning Auger electron microscopy were obtained by Monte Carlo calculations including secondary electron generation. In the low‐energy region, the cross sections calculated by the partial wave expansion method were used instead of the screened Rutherford cross section to describe the elastic scattering process. The result suggests that secondary electrons of high energy are a significant source of Auger signals, particularly LVV‐Auger electrons, in scanning Auger electron microscopy. View full abstract»

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  • A new method determining migration distance of electrons and holes in insulators

    Page(s): 694 - 696
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    It is proposed that the average migration distance L of electrons and holes in insulators can be determined from electron‐hole recombination at activator ions acting as internal and radiative recombination centers. This is demonstrated for Y2O3. One‐dimensional migration (along a line) rather than three‐dimensional spreading is found; L = dC-1, where d is the cation‐cation distance and C is the activator concentration in mole fraction. 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