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1 Jan 1969

Volume 40, Issue 1, pp. 1-446

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Lateral Diffusion in Ag☒Se Thin‐Film Couples

D. B. Johnson and L. C. Brown

J. Appl. Phys. 40, 149 (1969); http://dx.doi.org/10.1063/1.1657020 (4 pages) | Cited 8 times

Online Publication Date: 17 November 2003

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A study has been made of the diffusion of Ag along thin evaporated Se films using optical and transmission electron microscopy. The effect on the growth rate of varying both the Ag and Se film thicknesses and the temperature has been studied. Thin‐film diffusion rates were considerably faster than in bulk diffusion couples, indicating some short‐circuit diffusion mechanism. An important result of the investigation was the demonstration of a critical thickness ratio of Ag to Se which had to be exceeded in order for diffusion to occur. This critical ratio depended only on the stoichiometry of the Ag2Se phase formed during diffusion.

Power Radiated by Oscillating Magnetic and Oscillating Electric Dipoles in a Cold, Streaming Plasma

John E. Bergeson

J. Appl. Phys. 40, 152 (1969); http://dx.doi.org/10.1063/1.1657022 (7 pages)

Online Publication Date: 17 November 2003

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The power radiated by oscillating magnetic and oscillating electric point dipoles is calculated for the case where the dipoles are immersed in a cold, streaming plasma. The power output of the dipoles in a streaming plasma is less than it is in a stationary plasma, although the correction term is of order β2, where β is the ratio of the plasma's streaming velocity to the velocity of light. The power output is calculated by a generalized Poynting vector method, using electromagnetic‐field expressions derived from a set of linearized, covariant cold‐plasma equations. The results of this paper are compared with the results of Daly, Lee, and Papas, and of McKenzie, who calculate the power output of the oscillating electric dipole from a ``dispersive medium'' point of view.

Transient Color Centers in Fused Quartz

J. F. Holzrichter and J. L. Emmett

J. Appl. Phys. 40, 159 (1969); http://dx.doi.org/10.1063/1.1657023 (5 pages) | Cited 7 times

Online Publication Date: 17 November 2003

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Transient color centers, induced by pulses of uv light, have been observed in fused quartz. The absorption peaks appear to agree with the wavelengths of the weaker permanent coloration. The band at 3000 Å has a lifetime of 0.38 milliseconds; that at 5000 Å has a lifetime of about 12 sec.

Temperature Dependence of the Energy Gap in GaAs and GaP

M. B. Panish and H. C. Casey

J. Appl. Phys. 40, 163 (1969); http://dx.doi.org/10.1063/1.1657024 (5 pages) | Cited 137 times

Online Publication Date: 17 November 2003

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Absorption measurements from 300°–973°K for GaAs and to 1273°K for GaP were made in order to determine the energy gap Eg of these materials at high temperatures. These data, together with previously published results, show that the energy‐gap width may be represented by a simple expression for all temperatures. As a function of the absolute temperature T, the direct gap in GaAs is given by Eg=1.522−5.8×10−4T2 ∕ (T+300) eV, and the indirect gap in GaP is given by Eg=2.338−6.2×10−4T2 ∕ (T+460) eV. The general form of the expression for the energy gap is Eg=Eg(0)−aT2 ∕ (T+β), where Eg(0) is the energy gap at 0°K, β is approximately the 0°K Debye temperature, and a is an empirical constant.

Formation Energy of Individual Cation Vacancies in LiF and NaCl

O. S. Spencer and C. A. Plint

J. Appl. Phys. 40, 168 (1969); http://dx.doi.org/10.1063/1.1657025 (5 pages) | Cited 6 times

Online Publication Date: 17 November 2003

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The formation energy g+ of an individual cation vacancy in LiF and NaCl has been measured by means of the temperature dependence of the electrical signals produced by push‐pull deformation of bent crystals and application of the theory of charged dislocations. For LiF: g+=0.74±0.04 eV at 680°K. For NaCl: g+=0.75±0.04 eV at 627°K and 0.72±0.04 eV at 761°K. A comparison with other published results for NaCl reveals some unexplained disagreement.

Threshold Microwave‐Field Amplitude for the Unstable Growth of Spin Waves under Oblique Pumping

J. J. Green, C. E. Patton, and E. Stern

J. Appl. Phys. 40, 172 (1969); http://dx.doi.org/10.1063/1.1657026 (6 pages) | Cited 11 times

Online Publication Date: 17 November 2003

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The threshold microwave‐field amplitude hcrit required for the unstable growth of spin waves has been investigated for oblique pumping with a linearly polarized microwave field applied at an arbitrary angle with respect to the static magnetic field. The experiment was performed on YIG (1% Dy) spheres at 9.2 GHz, using a rectangular TE102 cavity and a pulsed magnetron source. Data were obtained at static external fields of 400, 600, 1100, and 1500 Oe. In general, hcrit increases with the pump angle. Theoretical expressions for the oblique pumping hcrit have been derived for ferromagnetic insulators of ellipsoidal shape and with axial symmetry about the direction of the static magnetic field sufficient to saturate the sample. The threshold field is determined by maximizing 1∕h=cosψ∕h∥±sinψ∕h⊥ with respect to the angle between the internal field and the spin‐wave propagation direction. Here, h∥ and h⊥ are the parallel and perpendicular pump threshold fields of Schlömann and Suhl. For external fields sufficient to magnetize the spherical samples to saturation, the theoretical predictions are in good agreement with the experimental data. For small fields, the agreement is poor. However, fair agreement is obtained by assuming a transverse demagnetizing factor Nt greater than the value of ⅓, which is appropriate for saturated spherical samples. The value of Nt for the best theoretical fit depends on the way in which the sample is demagnetized. This result indicates that for samples not magnetized to saturation, the magnetic structure consists of elongated domains, and that the oblique‐pumping data can be explained from the theory for saturated systems, assuming demagnetizing factors appropriate to the domain structure.

Steady‐State Gain of Stimulated Brillouin Scattering in Liquids

F. Barocchi

J. Appl. Phys. 40, 178 (1969); http://dx.doi.org/10.1063/1.1657027 (3 pages) | Cited 6 times

Online Publication Date: 17 November 2003

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The S.B.S. steady‐state gain is derived taking into account the energy‐transfer relaxation properties of the liquids. Calculation of the gain for C6H6 and CCl4 are performed. Quantitative comparison between experimental and theoretical gain in n‐hexane, ethyl‐ether, and CS2 are also derived.

Dislocation Arrangements in Fluorapatite

G. M. McManus, R. H. Hopkins, and W. J. Takei

J. Appl. Phys. 40, 180 (1969); http://dx.doi.org/10.1063/1.1657028 (4 pages) | Cited 5 times

Online Publication Date: 17 November 2003

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Some observations on the microstructure of Czochralski‐grown fluorapatite, Ca5F(PO4)3, single crystals are presented. From etching and x‐ray topographic studies we have found that slip in this material is on (1010) planes, with one Burgers vector in the c direction, and another in the basal plane and probably along the [1010] direction.

Response Characteristics of Extrinsic Photoconductors

R. L. Williams

J. Appl. Phys. 40, 184 (1969); http://dx.doi.org/10.1063/1.1657029 (9 pages) | Cited 19 times

Online Publication Date: 17 November 2003

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The speed of response of extrinsic germanium photoconductors is limited by the dielectric relaxation response time τρ=ϵϵ0ρ, when the resistivity of the photoconductor rises to the MΩ⋅cm or higher resistivity range. Further, dielectric relaxation components appear only when the drift length of charge carriers is comparable to or greater than the interelectrode distance. The appearance of the dielectric relaxation response‐time component arises when a significant fraction of the photogenerated charge carriers is swept out of the photoconductor before recombination leaving a space charge throughout the crystal. For mercury‐and copper‐doped germanium photoconductors which were studied, an enhanced photosensitivity is observed with increasing bias. For low backgrounds, or high‐resistivity conditions, the effect is largest and appears to correlate with the onset of the dielectric relaxation effects.

New Method of Obtaining Volume, Grain‐Boundary, and Surface Diffusion Coefficients from Sintering Data

D. Lynn Johnson

J. Appl. Phys. 40, 192 (1969); http://dx.doi.org/10.1063/1.1657030 (9 pages) | Cited 145 times

Online Publication Date: 17 November 2003

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A sintering model is proposed by which all of the significant mechanisms of material transport may be identified, even though more than one mechanism may be operating simultaneously. For diffusion‐controlled sintering it is possible to calculate both the volume and the grain‐boundary diffusion coefficients from measurements of neck size, shrinkage, and shrinkage rate. Furthermore, the surface diffusion coefficient may be estimated through computer synthesis of the sintering curves. Preliminary results on iron and copper have yielded values of the diffusion coefficients which are in good agreement with those measured by other techniques.

Dispersion‐Corrected Three‐Wavelength Laser Heterodyne Measurement of Plasma Densities

C. S. Liu, J. T. Verdeyen, and B. E. Cherrington

J. Appl. Phys. 40, 201 (1969); http://dx.doi.org/10.1063/1.1657031 (7 pages) | Cited 5 times

Online Publication Date: 17 November 2003

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A three‐wavelength laser heterodyne system for plasma diagnostics has been developed using the 0.6328, 1.15, and 3.39 μ transitions in He☒Ne. In order to use the 3.39 μ transition, an experimental technique has been developed to measure the dispersion introduced by the lasering atoms under the same conditions that are used for plasma measurements. The dispersion‐corrected 3.39 μ data, when combined with the data at 1.15 and 0.6328 μ, give excellent agreement in the measurement of temporally and spatially resolved electron densities and changes in neutral densities in the afterglow of a pulsed argon discharge. The electron‐density measurements agree with integrated electron‐density measurements made with a microwave cavity operating in the TM010 mode.

Elastic and Anelastic Behavior during the Martensitic Transformation in Indium‐Thallium Alloys

M. E. de Morton

J. Appl. Phys. 40, 208 (1969); http://dx.doi.org/10.1063/1.1657032 (5 pages) | Cited 20 times

Online Publication Date: 17 November 2003

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Measurement of internal friction at strain amplitudes <10−5 in In‐rich In☒Tl alloys has shown an amplitude‐dependent peak associated with the fcc→fct martensitic transformation. The peak is thermally activated when the transformation occurs near the melting point Tm, but not at lower temperatures. It is suggested that the peaks originate from the stress‐assisted motion of twin boundaries that are known to spontaneously coalesce immediately below the transformation temperature. The activation energy associated with the transformation peak near Tm is 10–13 kcal∕mole higher than for the diffusion of Tl in In. A mechanism is proposed for this relaxation, invoking an interaction between twin boundaries and solute, whereby reordering of solute is effected in differently orientated tetragonal regions by twin‐boundary motion. Shear modulus measurements indicated abrupt changes at the transformation temperature and positive temperature coefficients of modulus in the high‐temperature fcc phase, implying structural instability and an ``entropy‐elastic'' state. At 0.9 Tm, about 60% of the elasticity in a 19.5% Tl☒In alloy arises from a change in vibrational entropy with extension. The results are consistent with the known crystallography of the transformation.

Structural and Optical Evaluation of Vacuum‐Deposited GaP Films

John E. Davey and Titus Pankey

J. Appl. Phys. 40, 212 (1969); http://dx.doi.org/10.1063/1.1657033 (8 pages) | Cited 18 times

Online Publication Date: 17 November 2003

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Optical absorption‐edge shifts of up to 1.5 eV have been observed for GaP films deposited in textured polycrystalline states and in the amorphous state. The amorphous‐crystalline transition occurs for a substrate temperature Ts of about 240°C. The films deposited at 240°C≤Ts≤270°C exhibiting the large optical absorption‐edge shift are nontransparent, metallic‐appearing, and exhibit a strong [110] texture. The amorphous films deposited at just below 240°C exhibit the same optical properties. With increasing Ts, the films exhibit decreasing optical absorption‐edge shifts, becoming transparent‐yellow for Ts≥425°C. However, a bulk optical behavior is achieved only by annealing the films at temperatures up to 600°C. The principal textures found by x‐ray diffraction are [110] for 240°≤Ts≤270°C, and [111] for Ts>350°C. Reflection‐electron‐diffraction (RED) observations agree substantially with those obtained by x ray, but also indicate some mixed textures. A weak (1010) reflection is observed by both x rays and RED, indicating an incipient hcp phase; it is shown that this is not causally related to the optical‐edge shift. X‐ray lattice‐constant measurements over the range of Ts from 250°–425°C indicate no observable systematic deviation from bulk values; these observations rule out any causal relationship between changes in lattice constant and the optical absorption‐edge shift. Extinction bands or bounded‐plasma resonance effects do not seem to be able to explain the experimental behavior; the shifts are most probably due to large concentrations of self‐compensated natural defects. It is emphasized that these as‐deposited and annealed GaP films cover the entire absorption spectrum (α vs E) of all III‐V compounds (except InAs and InSb) plus Ge and Si.

Efficient Second‐Harmonic Generation with Diffraction‐Limited and High‐Spectral‐Radiance Nd‐Glass Lasers

W. F. Hagen and P. C. Magnante

J. Appl. Phys. 40, 219 (1969); http://dx.doi.org/10.1063/1.1657034 (6 pages) | Cited 22 times

Online Publication Date: 17 November 2003

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Efficient second‐harmonic generation (SHG) at 5300 Å has been achieved with KDP and LiNbO3 crystals when Nd‐glass lasers of high radiance and narrow bandwidth were used. With KDP and a diffraction‐limited laser system having a 19 Å bandwidth, 15 J of radiant energy at 5300 Å were obtained with a 51% energy‐conversion efficiency. Since the harmonic light pulse was narrower than the fundamental pulse, the peak‐power‐conversion efficiency was 70%. The peak power in the green was 1.0 GW. The ratio of harmonic‐fundamental pulse duration increased as SHG increased into the saturation region as expected. For LiNbO3, the relatively large dependence of phase‐matching angle on wavelength limits the maximum SHG efficiency to several percent when broad‐band lasers are used. With LiNbO3, therefore, a laser system was used having mode selectors which limited the bandwidth to less than 0.5 Å while the beam divergence was 1.5 mrad. In this case 21% energy conversion and 33% peak‐power conversion were obtained with a fundamental flux density of only 2 MW∕cm2 inside the crystal. The values found for the elements of the nonlinear dielectric tensor, corrected for the random multimode nature of the laser, are d36(KDP) = (1.1±0.1)×10−9 esu and d31(LiNbO3) = (17±6)×10−9 esu. At low conversions a laser beam with fluctuations due to random multimoding is expected to give as much as twice the harmonic produced by a single‐mode laser. At high conversions in the saturation region this ``doubling'' does not occur as verified by our measurements.

Magnetic Susceptibility of ϵ and η Phase Alloys in the Silver‐Zinc System

S. Noguchi, T. Yoneyama, and T. B. Massalski

J. Appl. Phys. 40, 225 (1969); http://dx.doi.org/10.1063/1.1657036 (5 pages) | Cited 5 times

Online Publication Date: 17 November 2003

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Magnetic susceptibility measurements are reported in the range of the hcp ϵ and η phases of the Ag☒Zn system. The observed trend suggests that a minimum occurs in the magnetic susceptibility of the conduction electrons within the phase field of the ϵ phase at an electron concentration of approximately 1.8 electrons per atom. In the η phase the magnetic susceptibility increases rapidly, but the trend is less steep than that extrapolated from the ϵ phase. The results show certain similar features with the measurements of the lattice spacings and of thermodynamic properties reported in the literature. The magnetic susceptibility of the ϵ phase alloys can be related to the possible interactions between the Fermi surface and the Brillouin zone, but the behavior of the susceptibility in the η phase appears to be also dependent on local interactions between zinc atoms.

An Ag☒GaAs Schottky‐Barrier Ultraviolet Detector

R. D. Baertsch and J. R. Richardson

J. Appl. Phys. 40, 229 (1969); http://dx.doi.org/10.1063/1.1657037 (7 pages) | Cited 10 times

Online Publication Date: 17 November 2003

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Ag☒GaAs Schottky‐barrier photodiodes have been fabricated and evaluated as detectors of uv radiation. The quantum efficiency of these detectors is a maximum near 3225 Å, and is much less in the visible and ir regions of the spectrum. The peak quantum efficiency and selectivity of the detector is determined by the thickness of the silver layer, which possesses a narrow transmission ``window'' for radiation near 3225 Å wavelength. The transmittance of silver films evaporated on 7059 glass and quartz substrates was measured and compared with calculations based on previously published optical constants. At the transmittance peak, the extinction coefficient for these silver films was measured to be 0.38. From these transmittance measurements, the fraction of the radiation, incident on the silver, which enters the GaAs of the photodetectors was calculated as a function of wavelength and silver‐film thickness. This quantity was compared with the measured quantum efficiency of the diodes. At the peak, the comparison indicated that 25–50% of the carriers created within the depletion region of the barrier do not contribute to the photocurrent. Measurements of the dependence of quantum efficiency on bias and energy of the absorbed radiation suggest that at the peak, a fraction of the carriers created within the depletion layer are energetic enough to pass over the Schottky barrier and not be collected as photocurrent.

Mass‐Spectrometer Analysis of a Cesium Plasma

H. L. Witting

J. Appl. Phys. 40, 236 (1969); http://dx.doi.org/10.1063/1.1657038 (6 pages) | Cited 6 times

Online Publication Date: 17 November 2003

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An experiment has been performed in order to determine the dominant ionic species in a cesium plasma in the Torr pressure range. The device consists of a planar thermionic converter with a small (25 μ diam) hole in the collector. Ions that pass through the hole are accelerated by an ion gun and analyzed in a magnetic mass spectrometer. It is found that atomic cesium ions are the dominant species in both the ignited and unignited modes of operation of the discharge. The molecular cesium ions Cs2+ and Cs3+ were also detected in the ignited mode. In addition, measurements were made of the total ion and electron currents that pass through the collector hole. Here the hole acts as a probe of the plasma adjacent to the collector.

Radiative Tunneling in GaAs Abrupt Asymmetrical Junctions

H. C. Casey and Donald J. Silversmith

J. Appl. Phys. 40, 241 (1969); http://dx.doi.org/10.1063/1.1657039 (16 pages) | Cited 19 times

Online Publication Date: 17 November 2003

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A representative number of abrupt GaAs junctions, asymmetrically doped, have been studied to delineate quantitatively the properties of spectra (called shifting‐peak spectra) whose peak energy approximately equals the applied voltage V, and shifts in position and intensity with V. The free‐electron concentration n on the more lightly doped side was varied from 3×1017 cm−3 to 8×1018 cm−3, the voltage range was ∼1.0 to ∼1.5 V, and the temperature was varied from 12° to 255°K. Because the active region width is 600 Å or less, and the spectral shape agrees in all details with Morgan's theory of photon‐assisted tunneling, these shifting‐peak spectra have been identified as radiative tunneling. It is shown here that no adjustable parameters are needed to calculate the experimental spectral shape when only T, V, and n are specified. This means that for any given temperature, n alone represents the influence of the junction on the spectral shape, while the independent parameter in terms of excitation is the voltage and not the current, as usually stated. The agreement between the calculated and experimental spectra includes the logarithmic slope of the low energy tail, and the difference between V and the energy of the peak‐emission intensity hvp: eV0=eV‐hvp. This agreement emphasizes the necessity of including the parabolic junction potential as obtained from Poisson's equation when calculating the tunneling‐hole and electron‐wave functions. The usual simplifying assumption of a linear potential is inadequate. To clarify previous observations of one or two types of shifting‐peak spectra, linear‐graded and abrupt‐asymmetrical junctions were made from adjacent wafers of the same crystal, and the resulting shifting‐peak spectra were compared. Only band‐to‐band radiative tunneling was observed for the abrupt junction, but for the linear‐graded junction two shifting‐peak spectra were observed. In the low excitation region for linear‐graded junctions, the shifting‐peak spectra may be described by band‐to‐impurity radiative tunneling that results in a narrow active‐region width, while at higher bias the emission becomes band‐to‐band radiative tunneling with a wider active region. These results demonstrate that shifting‐peak spectra previously attributed to band filling may be described in terms of photon‐assisted tunneling.

Ionic Analysis of Cataphoresis in He☒Ne Mixtures

J. P. Gaur and L. M. Chanin

J. Appl. Phys. 40, 256 (1969); http://dx.doi.org/10.1063/1.1657040 (9 pages) | Cited 23 times

Online Publication Date: 17 November 2003

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For studies of cataphoresis in He☒Ne mixtures, an analytic expression is derived for the functional dependence of the neon atoms in the axial direction. The analysis, which involves the continuity equation, considers the production and loss mechanisms of the Ne+ ions. The present theory can be used to predict the degree of ionization of neon at a given pressure and current, when the appropriate rate coefficients are known. In addition, techniques for ion sampling from gaseous plasmas have been used in the present investigation. Measurements have been made in commercial helium‐gas samples having a quoted neon concentration ≤0.001% and in samples containing 0.05% neon. Studies were conducted over a pressure and current range of 7–30 Torr and 8–80 mA, respectively. Depending on the experimental conditions, the following ions were observed: He2+, Ne+, Ne2+, and HeNe+. For the case of HeNe+, the present studies permit an estimate of the rate coefficient for the reaction Ne++2He→HeNe++He which is comparable to values obtained from afterglow studies. Measured values of the degree of ionization are in good agreement with values calculated using the present theory.

The Measurement of the Erosion Rate at the Electrodes of an Arc Rotated by a Transverse Magnetic Field

J. E. Harry

J. Appl. Phys. 40, 265 (1969); http://dx.doi.org/10.1063/1.1657041 (6 pages) | Cited 12 times

Online Publication Date: 17 November 2003

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The measurement of the erosion at the electrodes of an arc rotated between water‐cooled nonrefractory coaxial electrodes in an axial magnetic field has been made in air at atmospheric pressure. Values of erosion rate an order‐of‐magnitude less than those previously reported have been obtained. The effect of variation in axial magnetic flux density, arc velocity, rotational frequency, cooling‐water flow‐rate, and electrode wall thickness have been investigated. A steady‐state model, taking into account the nonuniform thermal distribution in the electrode below the arc root, has been obtained in terms of the electrode dimensions normalized with respect to the diameter of the arc root. The minimum conditions for the surface of a cold‐cathode electrode to be maintained below the melting point of the electrode material are deduced.

Interaction of Li and O with Radiation‐Produced Defects in Si

R. C. Young, J. W. Westhead, and J. C. Corelli

J. Appl. Phys. 40, 271 (1969); http://dx.doi.org/10.1063/1.1657042 (8 pages) | Cited 17 times

Online Publication Date: 17 November 2003

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The interaction of Li atoms with O impurities and with defects produced in Si by 1.5 MeV and 47 MeV electrons was studied using infrared spectroscopy. Li was diffused in low oxygen‐containing uncompensated Si with initial resistivity in the range 15–28 500 Ω⋅cm and in high oxygen‐containing Si with initial resistivity of 15–200 Ω⋅cm. The Li concentration in the samples varied from about 1016 to ≲1019 Li atoms∕cm3. New radiation‐induced bands at 1.4 and 1.7 μ are observed. Divacancy production as measured by the 1.8 and 3.3 μ defect bands is markedly decreased in samples of high Li content with concomitant growth of the Li‐associated 1.4 and 1.7 μ bands. Annealing of the 1.4 and 1.7 μ bands strongly depends upon the Li concentration. Recovery occurs at a temperature of 150°C for the 1.4 μ band, and at 350°C for the 1.7 μ band, for samples containing ∼6×1017 Li∕cm3. In samples containing ∼2×1016Li∕cm3, the bands at 1.4 and 1.7 μ disappear after annealing at 330° and 470°C, respectively. Sharp Li‐ and O‐associated defect bands in the 700–1000 cm−1 range are produced only in high O‐containing samples, and the presence of Li has a pronounced effect on the production and recovery of the A‐center defect (830 cm−1 band). In samples of high Li content, the predominant absorption is due to free carriers and is found to be in agreement with predictions of theory. A search for defect absorption bands attributable to vibrational modes of the isolated interstitial Li+ ions yielded negative results.

Fowler‐Nordheim Tunneling into Thermally Grown SiO2

M. Lenzlinger and E. H. Snow

J. Appl. Phys. 40, 278 (1969); http://dx.doi.org/10.1063/1.1657043 (6 pages) | Cited 500 times

Online Publication Date: 17 November 2003

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Electronic conduction in thermally grown SiO2 has been shown to be limited by Fowler‐Nordheim emission, i.e., tunneling of electrons from the vicinity of the electrode Fermi level through the forbidden energy gap into the conduction band of the oxide. Fowler‐Nordheim characteristics have been observed over more than five decades of current for emission from Si, Al, and Mg. If previously measured values of the barrier heights are used, the slopes of the Fowler‐Nordheim characteristics (log J∕E2 vs 1∕E) imply values of the relative effective mass in the forbidden band of about 0.4. These values take into account corrections for image‐force barrier lowering and for temperature effects. The absolute values of the currents are lower by a factor of five to ten than the theoretically expected values, probably due to trapping effects. The temperature dependence of the current was found to follow the theoretical curve from 80°–420°K. However, an inconsistent relative effective mass of about 0.95 had to be assumed. These results are believed to provide the most complete examination of the Fowler‐Nordheim‐emission theory.

The Change in Work Function of the (100) Surface of Tungsten as O2, N2, CO2, and H2 are Adsorbed

A. E. Abey

J. Appl. Phys. 40, 284 (1969); http://dx.doi.org/10.1063/1.1657044 (4 pages) | Cited 5 times

Online Publication Date: 17 November 2003

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The change in work function of the (100) surface of a tungsten single crystal was measured as a function of time as gas adsorbed on the surface. Using a simple model, the work function changes for monolayer coverage were found to be 0.94 eV, −0.7 eV, 0.21 eV, and 0.44 eV, for O2, N2, H2, and CO2, respectively. The initial bare surface sticking probabilities were found to be 0.24, 0.37, 0.63, and 0.29, respectively. The initial changes in work function per molecule were found to be 9.4×10−16 eV, −7×10−16 eV, 2.1×10−16 eV, and 1.75×10−15 eV, respectively.

Dielectric Breakdown of Polymer Films

J. Blok and D. G. LeGrand

J. Appl. Phys. 40, 288 (1969); http://dx.doi.org/10.1063/1.1657045 (6 pages) | Cited 16 times

Online Publication Date: 17 November 2003

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Strong electric fields have been applied to dielectric polymer films to study field‐induced mechanical stresses. For voltages near breakdown the mechanical forces are sufficient to cause localized deformation in some polymer films. Considerable field enhancement can occur at the deformation sites, leading to reduced nominal dielectric strength for the samples. Experimental evidence for electromechanical deformation is presented as a possible explanation for the poor agreement between the observed dielectric strength and that predicted theoretically.

Correction of X‐Ray Diffraction Profiles for Instrumental Broadening in Transmission Geometry

Sabri Ergun

J. Appl. Phys. 40, 293 (1969); http://dx.doi.org/10.1063/1.1657046 (4 pages) | Cited 3 times

Online Publication Date: 17 November 2003

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When polychromatic radiation is used in x‐ray diffraction, the instrumental broadening changes with the scattering angle. It is shown that when transmission geometry is used, the instrumental broadening can be expressed in terms of the profile of the primary beam and its wavelength distribution. Consequently, it becomes possible to correct the entire intensity profile for instrumental broadening. The correction is made by successive foldings of the observed profile, and is demonstrated using the intensity profiles of raw and heat‐treated carbon black.
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