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15 Apr 1974

Volume 24, Issue 8, pp. 347-398


Preferred orientations in MgO films deposited on amorphous substrates

M. O. Aboelfotoh

Appl. Phys. Lett. 24, 347 (1974); http://dx.doi.org/10.1063/1.1655210 (3 pages) | Cited 9 times

Online Publication Date: 9 October 2003

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Reflection high‐energy electron diffraction patterns show that the crystal orientation of MgO films deposited on amorphous substrates at 30 °C at normal vapor incidence varies with film thickness. Films in the thickness range of 50 Å to less than 1000 Å have a random orientation. As the film thickness is increased a 〈 111 〉 preferred orientation develops. The 〈 111 〉 preferred orientation remains unchanged upon annealing in vacuum at a temperature in the range from 400 to 550 °C for 1 h. The origin of these orientations is discussed.

Alignment and wetting properties of nematic liquids

Ivan Haller

Appl. Phys. Lett. 24, 349 (1974); http://dx.doi.org/10.1063/1.1655211 (3 pages) | Cited 29 times

Online Publication Date: 9 October 2003

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Contrary to recent claims, no correlation of useful predicting power exists between the tendency of a nematic liquid to align transverse to a solid surface and the difference between the surface free energies of the nematic liquid and of the substrate. Observations that lead to this conclusion are reported for systems in which (i) the composition but not the surface tension of the nematic liquid, (ii) the adsorbed layer and hence the surface free energy of the substrate, and (iii) the temperature is varied.

Radiation hardening and pressure‐actuated charge release of electron‐irradiated Teflon electrets

B. Gross, G. M. Sessler, and J. E. West

Appl. Phys. Lett. 24, 351 (1974); http://dx.doi.org/10.1063/1.1655212 (3 pages) | Cited 6 times

Online Publication Date: 9 October 2003

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The radiation‐induced conductivity (RIC) of Teflon is greatly reduced after bombardment with massive doses of the order of 100 Mrad. Such a ``radiation‐hardened'' Teflon film can store a considerably larger amount of negative charge in vacuum than nonhardened Teflon films. The stored charge is, however, released within a short time when the dielectric is brought up to air pressure. This charge release occurs partly as disruptive internal discharge at pressures below 1 Torr and partly as continuous charge release at higher pressures.

A critique of a recent thin‐film field‐effect experiment using detached electrodes

W. Robert Sinclair and L. E. Murr

Appl. Phys. Lett. 24, 354 (1974); http://dx.doi.org/10.1063/1.1655213 (2 pages) | Cited 3 times

Online Publication Date: 9 October 2003

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As a result of a study of the dc electric field effect on vapor‐deposited metal films using electrodes detached from the substrate, Murr and Singh recently observed no significant effects for fields applied in the plane of the substrate, ranging from 10 to 103 V∕cm. It is demonstrated in the present paper that a linear gradient did not exist during these experiments, and that due to a counteracting influence of the displacement current, the potential gradient at the substrate surface probably approached zero almost instantaneously at elevated substrate temperatures. An analysis of the field conditions attendant to thin‐film field‐effect experiments with detached electrodes indicates that the effect of dc electric fields on nucleation and growth of vapor‐deposited thin films in such an experiment can only be established when the substrate temperature is relatively low.

Reaction rates for Pt on GaAs

D. J. Coleman, W. R. Wisseman, and D. W. Shaw

Appl. Phys. Lett. 24, 355 (1974); http://dx.doi.org/10.1063/1.1655214 (3 pages) | Cited 16 times

Online Publication Date: 9 October 2003

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The rate at which GaAs reacts with Pt has been determined at selected temperatures between 300 and 400 °C. The amount of GaAs reacted is determined by measuring the movement of the original Pt Schottky‐barrier contact into the GaAs. Data are presented which show the amount of GaAs reacted as a function of anneal time at several different temperatures. The reaction follows a parabolic rate law with activation energy of 1.6 eV. Some change in the electrical characteristics of the Schottky barrier is observed.

Auger and secondary electrons excited by backscattered electrons

K. Goto, K. Ishikawa, T. Koshikawa, and R. Shimizu

Appl. Phys. Lett. 24, 358 (1974); http://dx.doi.org/10.1063/1.1655215 (2 pages) | Cited 4 times

Online Publication Date: 9 October 2003

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The contribution of backscattered electrons to Auger and secondary electron yields was examined by in situ measurements while evaporating Be onto Cu substrate at constant rate of 1.2 Å∕min. The ratios βA and βs of Auger (KVV) and secondary yields of Be due to backscattered electrons to those due to primary electrons were experimentally obtained from the Auger and true secondary electron yields versus backscattering coefficient η curves, and were evaluated to be 1.6 and 4.4 at a primary energy of 1.0 keV, respectively. The backscattering factor r for Be (KVV Auger) was experimentally found to be 1.1 at a primary energy of 1.0 keV.

Performance of the all‐metal‐wall theta pinch

M. Naraghi

Appl. Phys. Lett. 24, 360 (1974); http://dx.doi.org/10.1063/1.1655216 (3 pages) | Cited 2 times

Online Publication Date: 9 October 2003

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An all‐metal‐wall theta pinch has been constructed by stacking 200 anodized aluminum rectangular rods in order to form a cylindrical shell. Measurements by magnetic probes have shown the separation of current sheet from the metal wall in cases where the potential difference between two adjacent rods has been 25 V. Temperature measurements in helium plasma have shown higher temperatures when metal is used rather than dielectrics.

Nonlinear correction to Ohm's law derived from Boltzmann's equation

R. H. Havemann, P. F. Engel, and J. R. Baird

Appl. Phys. Lett. 24, 362 (1974); http://dx.doi.org/10.1063/1.1655217 (3 pages) | Cited 1 time

Online Publication Date: 9 October 2003

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See Also: Erratum

Show Abstract
The validity of Ohm's law is examined for the case of electric fields which are changing either in amplitude or direction over distances comparable to one electron mean free path within a metal. By perturbing both the amplitude and spatial variation of the electric field, an approximate solution of Boltzmann's equation is obtained which yields a first‐order correction to Ohm's law that is, in general, not in the same direction as the linear J = σE term. The nonlinear term is quadratic in the electric field amplitude and depends on the spatial derivatives of the electric field.

CO2‐laser‐driven detonation waves in the presence of a strong magnetic field

W. Halverson

Appl. Phys. Lett. 24, 364 (1974); http://dx.doi.org/10.1063/1.1655218 (3 pages) | Cited 15 times

Online Publication Date: 9 October 2003

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CO2‐laser‐driven detonation fronts have been studied in low‐pressure hydrogen and helium with axial magnetic fields up to 88 kG. At pressures above 100 Torr the shock front propagates toward the laser and the magnetic field has no observable effect. At lower pressures and no field, plasma fronts move both toward and away from the laser. The 88‐kG field confines the plasma radially and causes the ``downstream'' front to disappear. The shock motion is well described by the modified detonation model of Daiber and Thompson.

Photoemission from surface centers

R. F. Pierret and B. B. Roesner

Appl. Phys. Lett. 24, 366 (1974); http://dx.doi.org/10.1063/1.1655219 (4 pages) | Cited 4 times

Online Publication Date: 9 October 2003

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A technique is described whereby photoemission from surface centers can be effectively isolated and carefully monitored. Electronic photoexcitation from interface states in the Si☒SiO2 system has been observed using the technique and a photocapture cross‐sectional area ∼ 1 × 10−19 cm2 has been measured for states positioned energetically in the upper central portion of the silicon band gap.

Reducing the effective height of a Schottky barrier using low‐energy ion implantation

J. M. Shannon

Appl. Phys. Lett. 24, 369 (1974); http://dx.doi.org/10.1063/1.1655220 (3 pages) | Cited 55 times

Online Publication Date: 9 October 2003

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A thin highly doped layer at the surface of a semiconductor has been used to increase the surface field of a Schottky barrier and reduce the barrier height by an amount insensitive to applied bias. The effective barrier height of Ni☒Si barriers of this type made using ion‐implantation techniques has been reduced by an amount in the range 0–0.2 eV without significant degradation of the reverse characteristic.

Efficient upconversion of long‐wavelength uv light into the 200–235‐nm band

G. A. Massey

Appl. Phys. Lett. 24, 371 (1974); http://dx.doi.org/10.1063/1.1655221 (3 pages) | Cited 9 times

Online Publication Date: 9 October 2003

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Phase‐matched nonlinear generation of the second harmonic of visible laser sources has been limited to wavelengths longer than about 230 nm because the dispersion of available materials with high ultraviolet transmission cannot be compensated by their birefringence. Parametric upconversion of uv in the range 250–325 nm to the 200–235‐nm band by mixing with a strong infrared signal can be accomplished with 90° phase matching in 45° z‐cut crystals of ADP. A particularly useful embodiment of this idea is the upconversion of dye laser second‐harmonic wavelengths by mixing with the 1.064‐μm output of the Nd:YAG laser. Preliminary experiments in upconverting 266‐nm light to 213 nm have demonstrated stable conversion efficiencies above 50% for this process with peak and average powers above 5 kW and 0.5 mW, respectively.

Subpicosecond kilowatt pulses from a mode‐locked cw dye laser

C. V. Shank and E. P. Ippen

Appl. Phys. Lett. 24, 373 (1974); http://dx.doi.org/10.1063/1.1655222 (3 pages) | Cited 82 times

Online Publication Date: 9 October 2003

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Subpicosecond pulses (0.5–1.0 psec) have been generated by passive mode locking of a composite medium dye laser. Both the gain medium and saturable absorber are placed in a single free‐flowing dye stream located near the center of the resonator. Peak pulse powers of several kilowatts have been obtained by acousto‐optically dumping the mode‐locked pulses from the optical cavity at repetition rates up to 105 pps.

Rotational relaxation rate constants for CO2

Ralph R. Jacobs, Kenneth J. Pettipiece, and Scott J. Thomas

Appl. Phys. Lett. 24, 375 (1974); http://dx.doi.org/10.1063/1.1655223 (3 pages) | Cited 29 times

Online Publication Date: 9 October 2003

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Rotational relaxation rate constants, krot, have been measured for the CO2 00°1 level in three kinds of amplifiers: one using CO2 alone and two others using mixtures of CO2☒He and CO2☒N2. The experiment consists of perturbing the CO2 00°1 level with a ∼2‐nsec saturating pulse at P(20) in the 10.4‐μ band and monitoring the subsequent repopulation of the J = 19 rotational state with a probe beam set at P(20) in the 9.4‐μ band. The determined rate constants are kCO2☒CO2 = 1.3±0.2, kCO2☒He = 0.6±0.1, and kCO2☒N2 = 1.2±0.2, all in units of 107 sec−1 Torr−1.

Photon drag and other emfs induced in tellurium by a TEA CO2 laser

G. Ribakovs and A. A. Gundjian

Appl. Phys. Lett. 24, 377 (1974); http://dx.doi.org/10.1063/1.1655224 (3 pages) | Cited 8 times

Online Publication Date: 9 October 2003

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The longitudinal photon drag signal has been isolated from other interfering emfs generated in high‐purity good‐quality tellurium single crystals illuminated by 10.6‐μ radiation from a pulsed TEA CO2 laser. The observed value of 10 mV∕MW cm−2 at room temperature for the photon drag signal with E∥c and its temperature dependence down to 125 °K agree with the generally accepted theoretical expression. At room temperature the heavy hole momentum relaxation time has been calcualted to be 1.7 × 10−13 sec. Signals corresponding to a third‐rank tensorial effect have been occasionally measured at low temperatures, particularly when defects or dislocations have been introduced into the samples.

Infrared waveguides in thin films of CdS

C. R. Stanley, W. Duncan, and J. A. McMurray

Appl. Phys. Lett. 24, 380 (1974); http://dx.doi.org/10.1063/1.1655225 (3 pages) | Cited 1 time

Online Publication Date: 9 October 2003

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Laser radiation at 1.15 μm has been guided in thin films of CdS which were evaporated onto both glass and quartz substrates in a UHV system. The infrared radiation was coupled into and out of the films by both prisms and ion‐etched gratings, and a minimum propagation loss for the TE0 mode of less than 5 dB cm−1 was measured. A small birefringence was observed in these experiments, Δn = nTM − nTE≃0.01.

Distortionless propagation of zero‐degree pulses in degenerate resonant medium

Eugene Y. C. Lu and L. E. Wood

Appl. Phys. Lett. 24, 382 (1974); http://dx.doi.org/10.1063/1.1655226 (3 pages) | Cited 3 times

Online Publication Date: 9 October 2003

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We give arguments to show that distortionless propagation of zero‐degree pulses is possible in an arbitrary degenerate resonant medium in agreement with recent experimental observation. In the case of overlapping Q (2) degeneracy, the analytic closed‐form solution with zero area is given. The predicted pulse shape depends in the relative occupation of the degenerate levels and should be observable experimentally.

Repetitively pulsed electron‐beam‐initiated chemical lasers from SF6☒H2 and SF6☒D2 mixtures

R. Aprahamian, J. A. Betts, J. H. S. Wang, R. H. Herrett, and R. W. Barth

Appl. Phys. Lett. 24, 384 (1974); http://dx.doi.org/10.1063/1.1655227 (3 pages) | Cited 1 time

Online Publication Date: 9 October 2003

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Up to 5 pulses∕sec repetitive operation has been achieved with an electron‐beam‐initiated SF6☒H2 chemical laser. Maximum laser energies of 250 mJ∕pulse have been obtained from an active volume of 244 m1 and a total pressure of 600 Torr. Lasing was also observed from SF6☒D2 mixtures with peak energies one‐half of those from SF6☒H2.

A broadly tunable cw laser using color centers

L. F. Mollenauer and D. H. Olson

Appl. Phys. Lett. 24, 386 (1974); http://dx.doi.org/10.1063/1.1655228 (3 pages) | Cited 31 times

Online Publication Date: 9 October 2003

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cw laser action in an optically pumped Li‐doped KCl crystal containing FA (II) centers has been demonstrated. The laser wavelength was continuously tunable over the range 2.6–2.8 μm. Pump power at threshold was 50 mW, and threshold powers in the submilliwatt range can be predicted for an improved cavity design. Laser action was obtained for crystal temperatures in the range 77≲T≲200 °K.

Singly resonant CdSe parametric oscillator pumped by an HF laser

Joel A. Weiss and Lawrence S. Goldberg

Appl. Phys. Lett. 24, 389 (1974); http://dx.doi.org/10.1063/1.1655229 (3 pages) | Cited 11 times

Online Publication Date: 9 October 2003

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A transverse excitation HF laser has been used to pump a singly resonant CdSe infrared parametric oscillator. Tunable output has been generated over the range 4.3–4.5 μm and 8.1–8.3 μm with peak powers of up to 800 W. By a combination of angle tuning and selection of HF pump wavelength, CdSe is phase matchable for generation of radiation from 3.0–4.8 μm and 7.8–22 μm.

Kinetics and mechanism of platinum silicide formation on silicon

J. M. Poate and T. C. Tisone

Appl. Phys. Lett. 24, 391 (1974); http://dx.doi.org/10.1063/1.1655230 (3 pages) | Cited 80 times

Online Publication Date: 9 October 2003

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The growth of platinum silicide layers has been observed using Rutherford backscattering. By simultaneous observation of the relative movement of the Pt2Si and PtSi interfaces, it is possible to deduce that Si is the diffusing species with the reaction occurring at either the Pt2Si☒Pt, PtSi☒Pt2Si, or PtSi☒Pt interfaces. Activation energies for the growth of the Pt2Si and PtSi layers are 1.6 eV. It is possible to interact Pt with Si by means of Ar ion bombardment; however, the reacted layer acts as a barrier to Si diffusion.

Effect of high‐temperature heat treatment on penetration depth of superconducting niobium

C. Varmazis, A. Joshi, T. Luhman, and Myron Strongin

Appl. Phys. Lett. 24, 394 (1974); http://dx.doi.org/10.1063/1.1655231 (2 pages) | Cited 10 times

Online Publication Date: 9 October 2003

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A discussion is given of the change in penetration depth λ at the surface of niobium with various heat treatments and of the causes of the large changes in λ. In particular, the distribution of oxygen in from the sample surface is discussed, along with the thermal faceting caused by heating niobium to high temperatures at pressures near 10−6 Torr.

Temperature dependence of exchange stiffness in garnet bubble films

J. C. Slonczewski, A. P. Malozemoff, and E. A. Giess

Appl. Phys. Lett. 24, 396 (1974); http://dx.doi.org/10.1063/1.1655232 (2 pages) | Cited 25 times

Online Publication Date: 9 October 2003

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The temperature dependence of the exchange stiffness is taken into account to predict the room‐temperature exchange stiffness of substituted YIG films for bubble applications. A simple theory leads to the linear relation of A(T,TN) = AYIG(T)[TN−T)∕(TN, YIG −T)] where AYIG(T) is the exchange stiffness of YIG at the ambient temperature T and A(T,TN) is the exchange constant at T of a film with Neél temperature TN. This relation is in reasonable agreement with the recent spin‐wave resonance data of Henry and Heinz.

Stroboscopic observation of magnetic bubble circuits using a gated image‐intensifier tube

G. P. Vella‐Coleiro and T. J. Nelson

Appl. Phys. Lett. 24, 397 (1974); http://dx.doi.org/10.1063/1.1655233 (2 pages) | Cited 7 times

Online Publication Date: 9 October 2003

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A technique using a gated image‐intensifier tube for stroboscopic viewing of magnetic bubble motion in field access devices is described. Adequate illumination of bubbles propagating in a 100‐kHz rotating field was obtained with a conventional microscope illuminator and a 50× objective using gate pulses as short as 0.5 μsec at repetition rates as low as 10 kHz. Observation of bubbles propagating through a chevron expander showed that lateral growth is asymmetric, indicating that an asymmetrically located bubble input port would give improved performance. Shorter pulses and higher repetition rates should permit observation of bubbles propagating in excess of 1 MHz.
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