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15 Jan 1974

Volume 24, Issue 2, pp. 45-103

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Structure of catalysts: Determination by EPR and Fourier analysis of the extended x‐ray absorption fine structure

Farrel W. Lytle, Dale E. Sayers, and Emmett B. Moore

Appl. Phys. Lett. 24, 45 (1974); http://dx.doi.org/10.1063/1.1655087 (3 pages) | Cited 19 times

Online Publication Date: 9 October 2003

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An alumina‐supported CuCr catalyst was examined with the extended x‐ray absorption fine‐structure (EXAFS) technique. This is a new technique which can determine the chemical states and near‐neighbor environments of the separate Cu and Cr atomic species. Cu was found to occupy both tetrahedral and octahedral sites in the supporting alumina lattice while Cr was found only in octahedral sites. The valence state was Cr+5 in the fresh catalyst which changed to Cr+6 in the exhaust‐cycled material. Confirmation of the valence state assignment was obtained by EPR. Fourier analysis of the EXAFS produced separate radial structure functions for the Cu and Cr atoms since the experiment measures the properties of the individual atomic species rather than those of the structure as a whole. Significant differences were observed by both techniques between fresh and exhaust‐cycled material.

Alignment mechanism in twisted nematic layers

G. D. Dixon, T. P. Brody, and W. A. Hester

Appl. Phys. Lett. 24, 47 (1974); http://dx.doi.org/10.1063/1.1655088 (3 pages) | Cited 19 times

Online Publication Date: 9 October 2003

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Twisted nematic displays have been constructed in areas up to 36 square inches. Alignment of the liquid crystals was achieved by the oblique evaporation of silicon monoxide or gold. The surface deposits were examined by electron microscopy which indicated that mechanical alignment occurred due to the presence of islands and holes on the surface. It was found that the contrast ratio of the display decreased as the evaporating angle decreased.

Observations on the formation and etching of platinum silicide

Myron J. Rand and James F. Roberts

Appl. Phys. Lett. 24, 49 (1974); http://dx.doi.org/10.1063/1.1655089 (3 pages) | Cited 23 times

Online Publication Date: 9 October 2003

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When thin‐film platinum and single‐crystal silicon are interdiffused, [inverted lazy s] 100 Å of SiO2 is found at the PtSi surface. The silica protects the silicide from attack by the aqua regia commonly used to remove unreacted Pt. If the silica is stripped, PtSi on Si will dissolve in aqua regia even faster than Pt. These findings are applicable to contact technology for silicon devices and integrated circuits.

Bilinear signal processing using acoustic surface waves

Michel Feldmann and Jeannine Henaff

Appl. Phys. Lett. 24, 52 (1974); http://dx.doi.org/10.1063/1.1655090 (3 pages) | Cited 3 times

Online Publication Date: 9 October 2003

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Nonlinear interactions between noncollinear ASW with exact phase matching provide a special kind of convolution and correlation, according to the ratio ω1∕ω2 of the input frequencies. It means that the time scale at the output port depending on this ratio, time compression or expansion can be achieved. The same device can be used for both correlation and convolution with equal NL conversion efficiency.

Mechanism of fast surface flashover in vacuum

R. A. Anderson

Appl. Phys. Lett. 24, 54 (1974); http://dx.doi.org/10.1063/1.1655091 (3 pages) | Cited 21 times

Online Publication Date: 9 October 2003

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Insulator samples of Plexiglas and alumina ceramic in vacuum have been subjected to high‐voltage pulses with rise times of a few nanoseconds. Breakdown paths were inclined to the electric field in the presence of a magnetic field normal to the insulator surface, analogous to the Hall effect for bulk conduction. These results, as well as measurements of the flashover propagation velocity, strongly support a model of the flashover mechanism based on secondary electron emission.

Neutron emission from a small 1‐kJ plasma focus

L. Michel, K. H. Schönbach, and Heinz Fischer

Appl. Phys. Lett. 24, 57 (1974); http://dx.doi.org/10.1063/1.1655092 (3 pages) | Cited 25 times

Online Publication Date: 9 October 2003

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Neutron emissions from a small 0.34–1.35‐kJ (10–20‐kV) plasma focus in D2 ranged between 1.2×106 and 2.8×108 neutrons per shot. Shapes of the neutron and the hard x‐ray pulses (half‐width [sine wave] 50 ns) agree, coinciding in time with the ``dip'' in the di∕dt pulse. The angular neutron emission appears to follow the assumptions of the target beam model. Optical filament structures in the 30‐ns‐duration focus could not be observed.

Propagation of x rays in waveguides

Eberhard Spiller and Armin Segmüller

Appl. Phys. Lett. 24, 60 (1974); http://dx.doi.org/10.1063/1.1655093 (2 pages) | Cited 44 times

Online Publication Date: 9 October 2003

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Waveguide structures and couplers for x rays are analyzed. Experimental results are given for the propagation of Cu Ka radiation in guides made of BN.

Memory switching in ion‐exchanged oxide glasses

D. Chakravorty

Appl. Phys. Lett. 24, 62 (1974); http://dx.doi.org/10.1063/1.1655094 (2 pages) | Cited 12 times

Online Publication Date: 9 October 2003

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Memory switching has been observed in the surface layers of certain multiphase glasses which have been subject to Na+⇄Ag+ ion exchange followed by a reduction treatment in hydrogen. A possible mechanism is discussed in the light of the microstructural characteristics of these glasses.

Refractive index of AlxGa1−xAs between 1.2 and 1.8 eV

H. C. Casey, D. D. Sell, and M. B. Panish

Appl. Phys. Lett. 24, 63 (1974); http://dx.doi.org/10.1063/1.1655095 (3 pages) | Cited 135 times

Online Publication Date: 9 October 2003

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The refractive indices of AlxGa1−xAs samples prepared by liquid‐phase epitaxy were determined from accurate double‐beam reflectance measurements. The variation of the refractive index with photon energy at room temperature was obtained for AlAs mole fractions between 0 ≤ x ≤ 0.38 in the spectral range 1.2–1.8 eV.

Second harmonic generation and infrared mixing in AgGaSe2

R. L. Byer, M. M. Choy, R. L. Herbst, D. S. Chemla, and R. S. Feigelson

Appl. Phys. Lett. 24, 65 (1974); http://dx.doi.org/10.1063/1.1655096 (4 pages) | Cited 35 times

Online Publication Date: 9 October 2003

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We have continuously tuned between 7 and 15 μm by mixing the output of a LiNbO3 parametric oscillator in the chalcopyrite AgGaSe2. We have doubled a CO2 laser with 2.7% efficiency which agrees very well with the expected efficiency and verifies the high optical quality of the 1.53‐cm‐long AgGaSe2 crystal. The measured transparency range, indices of refraction, and nonlinear coefficient of d36 = (3.7 ± 0.6) × 10−11 m∕V show that AgGaSe2 is a useful infrared nonlinear material phase matchable over the entire 3–18‐μm infrared region.

Optical filter using a vapor mirror

Benjamin Senitzky

Appl. Phys. Lett. 24, 68 (1974); http://dx.doi.org/10.1063/1.1655097 (3 pages) | Cited 2 times

Online Publication Date: 9 October 2003

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The characteristics of a mercury vapor filter based on the principle of selective specular reflection are described. The filter passband is in the region of 2536.5 Å and its bandwidth can be varied from 0.1 to 1 Å by changing the vapor pressure. The device is used in an atomic emission flame photometer. A photograph of the distribution of Hg* in the flame is also obtained.

Submillimeter detection and mixing using Schottky diodes

H. R. Fetterman, B. J. Clifton, P. E. Tannenwald, and C. D. Parker

Appl. Phys. Lett. 24, 70 (1974); http://dx.doi.org/10.1063/1.1655098 (3 pages) | Cited 29 times

Online Publication Date: 9 October 2003

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Schottky diodes have been used for the first time as harmonic mixers in the 0.1–1.0‐mm wavelength region. Beat notes between the 33rd harmonic of a 74‐GHz V‐band klystron and 118.8‐μ laser radiation are observed directly without the need of narrow‐band synchronous detection. The demonstrated performance of these room‐temperature diodes as wide‐band or heterodyne detectors of submillimeter radiation and their rugged construction make them superior to current point contact devices.

Photolocking‐A new technique for fabricating optical waveguide circuits

E. A. Chandross, C. A. Pryde, W. J. Tomlinson, and H. P. Weber

Appl. Phys. Lett. 24, 72 (1974); http://dx.doi.org/10.1063/1.1655099 (3 pages) | Cited 32 times

Online Publication Date: 9 October 2003

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Low‐loss dielectric optical waveguides have been made by a new process in which a photochemical reaction is used to lock or fix a dopant in a polymer film with a lower refractive index, and unreacted dopant is then removed by heating. Narrow guides ([inverted lazy s]4 μm wide, Δn [inverted lazy s] 1%) were formed by laser beam writing at λ=364 nm or by contact printing at λ=313 nm, and had losses of 0.20±0.05 dB∕cm at λ=633 nm.

Metal oxide varistor‐A multijunction thin‐film device

Lionel M. Levinson and H. R. Philipp

Appl. Phys. Lett. 24, 75 (1974); http://dx.doi.org/10.1063/1.1655100 (2 pages) | Cited 30 times

Online Publication Date: 9 October 2003

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The physical origin of the highly nonlinear current‐voltage relation in metal oxide varistors is shown to be consistent with Fowler‐Nordheim tunneling.

Composition dependences of the energy gap and the green‐band emission peak for the AlxGa1−xP ternary system

H. Sonomura, T. Nanmori, and T. Miyauchi

Appl. Phys. Lett. 24, 77 (1974); http://dx.doi.org/10.1063/1.1655101 (2 pages) | Cited 16 times

Online Publication Date: 9 October 2003

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The AlxGa1−xP alloys having compositions up to x = 0.74 are prepared by slow cooling from Ga‐rich Al☒Ga☒P solutions. The composition of the alloy is accuratley determined from the density measured by using the flotation method. The alloy composition almost corresponds to the atomic ratio of Al to P in the initial mixture. The energy gap and the green‐band emission peak of the alloy vary linearly to the higher‐energy side as the Al concentration increases.

Silicon as a residual donor in high‐purity GaAs

C. M. Wolfe, D. M. Korn, and G. E. Stillman

Appl. Phys. Lett. 24, 78 (1974); http://dx.doi.org/10.1063/1.1655102 (3 pages) | Cited 19 times

Online Publication Date: 9 October 2003

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The question regarding the role of silicon as a residual impurity in high‐purity GaAs is resolved by the use of careful doping experiments and high‐resolution far‐infrared spectroscopy. The results indicate that silicon is readily incorporated into the material as a simple substitutional donor with a binding energy of 5.854 meV and show that silicon is a major, but not necessarily the dominant, residual donor in high‐purity vapor and liquid epitaxial GaAs.

Optical gating and logic with pyroelectric crystals

A. M. Glass and T. J. Negran

Appl. Phys. Lett. 24, 81 (1974); http://dx.doi.org/10.1063/1.1655103 (2 pages) | Cited 9 times

Online Publication Date: 9 October 2003

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Optical gating with LiTaO3 single crystals is demonstrated using an absorbing LiTaO3:Cr detector directly coupled to a LiTaO3 electro‐optic modulator. Since no electrical power is required, such a gating scheme provides a simple basis for optical logic in pyroelectric waveguides.

Room‐temperature laser operation of InxGa1−xAs p‐n junctions

C. J. Nuese, R. E. Enstrom, and M. Ettenberg

Appl. Phys. Lett. 24, 83 (1974); http://dx.doi.org/10.1063/1.1655104 (3 pages) | Cited 11 times

Online Publication Date: 9 October 2003

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Room‐temperature laser diodes which emit coherent infrared radiation near 1.1 μm have been prepared from InxGa1−xAs (x [inverted lazy s]0.23) vapor‐grown p‐n junction structures. At 77°K, laser threshold current densities as low as 1210 A∕cm2 and external differential quantum efficiencies as high as 50% have been obtained at 1.08 μm. At 300°K, the threshold current densities are between 70 000 and 98 000 A∕cm2 for emission at 1.145 μm.

New method for electro‐optical tuning of tunable lasers

John M. Telle and C. L. Tang

Appl. Phys. Lett. 24, 85 (1974); http://dx.doi.org/10.1063/1.1655105 (3 pages) | Cited 25 times

Online Publication Date: 9 October 2003

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A new scheme for electro‐optical tuning of tunable lasers is described. Tuning rates and tuning ranges in cw dye lasers nearly 100 times greater than those previously reported using a comparable‐sized electro‐optical crystal have been achieved using this method.

A limitation for nanosecond CO2 pulse amplification

Y. L. Pan, J. R. Simpson, and A. F. Bernhardt

Appl. Phys. Lett. 24, 87 (1974); http://dx.doi.org/10.1063/1.1655106 (4 pages) | Cited 3 times

Online Publication Date: 9 October 2003

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We have determined experimentally a limitation for nanosecond CO2 pulse amplification at atmospheric pressure in 5:1:1 He:CO2:N2 gas mixtures. We find that the refraction effect, self‐defocusing, will present difficulties both in the amplification of a nanosecond CO2 laser pulse to substantial energies and in subsequent laser fusion experiments where the laser beam is to be focused onto a target.

Gain saturation and self‐focusing considerations in the design of optical amplifiers

C. James Elliott

Appl. Phys. Lett. 24, 91 (1974); http://dx.doi.org/10.1063/1.1655107 (3 pages) | Cited 2 times

Online Publication Date: 9 October 2003

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We extend the stability analysis of the quasioptical equation given by Bespalov and Talanov and by Suydam to the case of Frantz‐Nodvik pulse propagation. When ϵ ≈ (An0g0/2πλ)2≪1, we find that the logarithm of the perturbation growth divided by the input intensity depends on the input illuminance and the media gain. This relationship is important in amplifier design. The asymptotic growth may be given in closed form even when ϵ≫1. This form is used for design refinements when indicated by an a posteriori estimate.

Trapping and absorption of an axially directed CO2 laser beam by a θ‐pinch plasma

Noel A. Amherd and George C. Vlases

Appl. Phys. Lett. 24, 93 (1974); http://dx.doi.org/10.1063/1.1655108 (3 pages) | Cited 22 times

Online Publication Date: 9 October 2003

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A deuterium‐filled θ pinch was axially irradiated in the first half‐cycle by a CO2 laser to demonstrate the effects of beam trapping and absorption by a plasma. Peak electron densities were 5×1016 cm−3 and the nonirradiated axial temperature was about 1.3 eV. Detection of the laser radiation transmitted through the plasma showed that beam trapping occurred when the density profile had a minimum on axis, and the maximum laser‐induced temperature increase of 2 eV occurred for irradiation at the time of maximum density, in agreement with inverse bremsstrahlung predictions. Furthermore, the plasma emission histories indicated that the column underwent a laser‐induced elongation of up to twice its original length.

Application of an organic dye for wavefront multiplication

T. Sawatari and D. M. Shupe

Appl. Phys. Lett. 24, 95 (1974); http://dx.doi.org/10.1063/1.1655109 (3 pages) | Cited 3 times

Online Publication Date: 9 October 2003

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An application of a dye solution for wavefront multiplication is described. In this application, two coherent pumping laser beams generate a spatial gain and index‐of‐refraction distribution in a dye amplifier. This distribution is used to modulate the amplitude and phase of an optical field in the amplification band of the dye in order to form a new wavefront. To establish that the multiplication is due to singlet‐state effects and not to triplet‐state excitation, the lifetime of the information in the dye cell is measured.

Observation of magnetic domains in nickel using the scanning electron microscope

D. E. Newbury, H. Yakowitz, and N. C. Yew

Appl. Phys. Lett. 24, 98 (1974); http://dx.doi.org/10.1063/1.1655110 (1 page) | Cited 4 times

Online Publication Date: 9 October 2003

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Scanning electron microscope (SEM) observation of magnetic domains in a polycrystalline pure nickel sheet was made possible through the use of a 50‐kV accelerating potential. The contrast was unobservable in an SEM capable of only a 30‐kV accelerating potential.

Effects of ion radiation damage on the magnetic domain structure of amorphous Gd☒Co alloys

R. J. Gambino, J. Ziegler, and J. J. Cuomo

Appl. Phys. Lett. 24, 99 (1974); http://dx.doi.org/10.1063/1.1655111 (3 pages) | Cited 29 times

Online Publication Date: 9 October 2003

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We have subjected sputtered amorphous films of Gd☒Co alloys to a high‐energy argon ion flux to study the effects of ion radiation damage on the uniaxial anisotropy of these materials. We find that a relatively low level of radiation damage ([inverted lazy s] 1014 ions∕cm2) can destroy the uniaxial anisotropy if the damage is sustained in zero applied fields. A similar dosage can induce anisotropy if a strong magnetic field is applied during the ion irradiation. These experiments support the atomic‐pair‐ordering model of anisotropy in these materials.
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