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1 May 1976

Volume 47, Issue 5, pp. 1741-2244

Page 1 of 4 Pages Next Page | Jump to Page

Storage and examination of high‐resolution charge images in Teflon foils

J. Feder

J. Appl. Phys. 47, 1741 (1976); http://dx.doi.org/10.1063/1.322884 (5 pages) | Cited 7 times

Online Publication Date: 28 August 2008

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High‐resolution charge patterns at various charge densities were written on Teflon TFE foils using a 10‐kV electron beam with a 1/2‐μm spot diameter. Resolutions of 50–100 line pairs/mm were observed by examination with an electron beam and use of xerographic development techniques. Charge spreading in the Teflon and the examination processes were among the factors limiting resolution. Development of stored patterns up to 3 months after their writing showed that resolutions of 100 line pairs can be maintained for this period. Comparison of the results for heat‐sealed samples with those for nontreated samples showed an absence of any marked pattern deterioration due to heat sealing.
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41.75.Fr Electron and positron beams
81.40.Rs Electrical and magnetic properties related to treatment conditions
73.90.+f Other topics in electronic structure and electrical properties of surfaces, interfaces, thin films, and low-dimensional structures (Restricted to new topics in section 73)

Lateral spread of damage formed by ion implantation

Hideki Matsumura and Seijiro Furukawa

J. Appl. Phys. 47, 1746 (1976); http://dx.doi.org/10.1063/1.322885 (6 pages) | Cited 14 times

Online Publication Date: 28 August 2008

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The lateral distribution of damage introduced in semiconductors by ion implantation is studied theoretically using the theory of Lindhard et al. This theoretical study is experimentally verified by a backscattering measurement of the damage formed by ion implantation into a tilted target. It is found that the spread of lateral damage is largest at a position near to or deeper than the ion projected range, and that the ratio of the lateral damage spread from a mask edge to the longitudinal damage spread from the surface is less than unity even in the case of implantation of light ions. For instance, the ratio is about 20% in the case of 100‐keV B+ implantation into Si. It is also found that the ratio becomes smaller as the energy of the implanted ions increases or as the ions become heavier.
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61.72.U- Doping and impurity implantation

Resistance variation and field effects in thin gold films after growth in an electric field

Thorwald Andersson

J. Appl. Phys. 47, 1752 (1976); http://dx.doi.org/10.1063/1.322886 (5 pages) | Cited 8 times

Online Publication Date: 28 August 2008

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The film resistance has been monitored during the deposition of gold onto glass at room temperature in UHV. The film structure during the growth could be related to the depositing resistance and to the resistance during aging after halts in the deposition. In the discontinuous stage the tunneling length of electrons increases exponentially with aging times larger than 2 h. The electric‐field‐dependent resistance was measured 20 h after deposition. An Ohmic region at low fields was followed by a region proportional to the square root of the applied field.
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73.61.At Metal and metallic alloys
68.55.-a Thin film structure and morphology

Structure and optical conductivity of thin lithium deposits prepared at 6 K

M. Rasigni, G. Rasigni, J. P. Gasparini, and R. Fraisse

J. Appl. Phys. 47, 1757 (1976); http://dx.doi.org/10.1063/1.322887 (5 pages) | Cited 6 times

Online Publication Date: 28 August 2008

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A replication technique is used to determine, in situ, the structure of thin lithium deposits prepared at 6 K. It is shown that perfectly smooth deposits are not always obtained. It follows, as in the case of deposits prepared at room temperature, that optical conductivity is not perfectly described by the sum of an intraband term and an interband term, but must take into account a supplementary term that characterizes an absorption due to granular structure of the deposit or to surface roughness defects. It is shown that certain deposits of lithium, prepared at low temperature, are made up of a two‐dimensional distribution of grains on a continuous layer of metal. In this case the supplementary term results from collective oscillations of conduction electrons in the metallic grains. From this, it can be concluded that most of the optical measurements made on the thin deposits of lithium (and on alkali metals in general) in all likelihood involve systematic errors, and should be corrected before being collated with theory.
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68.35.-p Solid surfaces and solid-solid interfaces: structure and energetics
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
68.55.-a Thin film structure and morphology

Pressure shear waves in fused silica

A. S. Abou‐Sayed and R. J. Clifton

J. Appl. Phys. 47, 1762 (1976); http://dx.doi.org/10.1063/1.322888 (9 pages) | Cited 8 times

Online Publication Date: 28 August 2008

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Simple wave solutions are presented for the case of pressure shear waves in a hyperelastic material which models fused silica. The adiabatic strain energy function of this material is written as an expansion to third‐order terms in the strains. The analysis includes interaction of the simple waves with a free surface. Comparison of computed particle velocity‐time profiles for the free surface with profiles observed in experiments shows good agreement. The solutions also indicate that the shear wave propagating in a shear‐strain‐free region of fused silica is essentially nondispersive.
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62.30.+d Mechanical and elastic waves; vibrations
46.40.Cd Mechanical wave propagation (including diffraction, scattering, and dispersion)
46.40.Jj Aeroelasticity and hydroelasticity
41.20.Jb Electromagnetic wave propagation; radiowave propagation
43.40.+s Structural acoustics and vibration

Optical dielectric constant of Pb1−xSnxTe in the narrow‐gap region

J. R. Lowney and S. D. Senturia

J. Appl. Phys. 47, 1771 (1976); http://dx.doi.org/10.1063/1.322889 (4 pages) | Cited 10 times

Online Publication Date: 28 August 2008

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The optical dielectric constant ϵ∞ of Pb1−xSnxTe has been measured for Sn fractions x of 0.0, 0.24, 0.36, 0.39, and 0.40 in the temperature range 6–120 K and at 300 K. The value of ϵ∞ increases from 33 for PbTe at 300 K to 60 for Pb0.61Sn0.39Te at 6 K. This maximum value appears to occur at a composition and temperature close to the L‐point band inversion. However, the relative insensitivity of ϵ∞ to carrier concentration suggests that this increase in ϵ∞ near band inversion arises from motion of the bands throughout the Brillouin zone rather than from a change in L‐point ionicity, as suggested by Wemple.
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78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
78.20.-e Optical properties of bulk materials and thin films

Temperature distribution on thin‐film metallizations

Yi‐Shung Chaug and Huei Li Huang

J. Appl. Phys. 47, 1775 (1976); http://dx.doi.org/10.1063/1.322890 (5 pages) | Cited 9 times

Online Publication Date: 28 August 2008

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The time‐dependent temperature distribution of a thin‐film stripe has been solved rigorously using two successive Laplace transforms on both time and coordinate. For a good conducting stripe with a δ‐shaped crack it is shown that the temperature distribution can be very adequately described by the steady‐state solution provided only that the time scale involved is of the order of 10−3 sec or longer. No localized hot spot is possible, for whatever reasons, for a good conductor. However, if heat generation outpaces heat conduction, as would be the case for a poor conductor, a localized temperature becomes quite realizable. Finally, if stripe cracking is developed via grain‐boundary grooving processes somewhere along the stripe, in particular near the anode, void formation there is simply a natural consequence of the temperature‐grandient effect.
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68.90.+g Other topics in structure, and nonelectronic properties of surfaces and interfaces; thin films and low-dimensional structures (restricted to new topics in section 68)
85.40.Bh Computer-aided design of microcircuits; layout and modeling
73.61.At Metal and metallic alloys

Electron‐microscope study of 10.6‐μm laser damage in GaAs

J. J. Comer

J. Appl. Phys. 47, 1780 (1976); http://dx.doi.org/10.1063/1.322891 (5 pages) | Cited 2 times

Online Publication Date: 28 August 2008

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The nature of the damage to GaAs caused by exposure to a 10.6‐μm laser beam at power densities of 1130, 2260, and 5650 W/cm2 was determined by transmission electron microscopy. At 5650 W/cm2 damage was observed at the surface in the form of craters of 80 μm or larger in diameter. Within the craters were found concentric zones spreading out from the center and consisting of (1) an amorphous region, (2) a region showing striations and skeletal crystalline walls in an amorphous matrix, and (3) a mixed amorphous‐crystalline region containing small rounded clusters of dislocations, some of which were helical. In one case crystalline arsenic was found near the central zone. The results observed at this power level indicate that thermal effects have caused melting, evaporation, and decomposition. It is suggested that the skeletal walls and the striations parallel to {110} planes are caused by preferential evaporation or decomposition and may be related to the presence of small precipitates or chemical inhomogeneities along {110} planes of GaAs as observed by others. Damage near the entrance surface at low power densities, and at the exit surface for the highest power density, consisted of unique clusters of dislocations spreading out along orthogonal 〈110〉 directions up to 3 μm. Although the direct cause of these dislocations could not be determined, it suggested that they result from cracking or cleavage of the crystal due to stresses caused by localized heating at sites of precipitates, occlusions, or other faults in the crystal.
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79.20.Ds Laser-beam impact phenomena
07.79.Cz Scanning tunneling microscopes
61.05.-a Techniques for structure determination
07.78.+s Electron, positron, and ion microscopes; electron diffractometers
61.72.Lk Linear defects: dislocations, disclinations

Positive and negative hydrogen ions backscattered from Au, Ta, and ThO2 in the energy range up to 15 keV

H. Verbeek, W. Eckstein, and S. Datz

J. Appl. Phys. 47, 1785 (1976); http://dx.doi.org/10.1063/1.322892 (5 pages) | Cited 18 times

Online Publication Date: 28 August 2008

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Samples of polycrystalline Au, Ta, and ThO2 were bombarded by 5–15‐keV beams of H+1, H+2, H+3, D+1, and D+3 ions. The backscattered positive and negative hydrogen ions were energy analyzed by a spherical condenser. For Au and Ta both the positive and the negative spectra start with zero intensity at zero energy and reach maxima, whose position depends on the primary energy and the ion species. For ThO2 the positive spectrum is similar but the number of negative ions shows no maximum and is largest at energies below 1 keV and continues to decrease with increasing energy. With decreasing work functions of the target materials the number of backscattered negative ions increases. The ratio of negative‐to‐positive backscattered ions is larger than unity at low energies in the cases of Au and ThO2. A comparison of proton and deuteron results shows that the ratio is equal for ions of equal velocities. For Ta and ThO2 this ratio is considerably larger when the targets are bombarded with molecular ions as H+2, H+3, D+2, and D+3 than when bombarded with the corresponding atomic ions H+ and D+ with equal energies per atom.
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79.20.Rf Atomic, molecular, and ion beam impact and interactions with surfaces
34.50.-s Scattering of atoms and molecules

Si depth profile and contaminants in Si‐doped Al film

C. C. Chang, T. T. Sheng, D. V. Speeney, and D. B. Fraser

J. Appl. Phys. 47, 1790 (1976); http://dx.doi.org/10.1063/1.322893 (5 pages)

Online Publication Date: 28 August 2008

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Si depth profiles and contaminants in Si‐doped Al films deposited on SiO2 by electron‐gun evaporation at different base pressures have been measured. The experimental techniques employed were Auger electron spectroscopy combined with ion milling for chemical analysis and depth profiling, and transmission electron microscopy for film structure studies. Auger analysis showed that at intended doping levels of 1 and 2 at.% (previously calibrated using atomic absorption spectrometry) the Al films contained 0.9 and 1.9 at.% Si, if the total Si content was averaged over the entire film thickness. However, most of the Si had migrated to the Al/SiO2 interface after deposition at 300 °C and formed precipitates which nucleated at or near the Al/SiO2 interface. The major film contaminants were C and O, whose concentrations were directly related to the pressure during deposition. The lowest detection limits with the Auger technique were ∼0.01 at.% (100 ppm) for both C and O, attained using a 50‐μA incident electron beam current and a scan time of <30 sec per element.
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68.55.-a Thin film structure and morphology
61.72.sd Impurity concentration
61.72.sh Impurity distribution
61.72.sm Impurity gradients
85.40.-e Microelectronics: LSI, VLSI, ULSI; integrated circuit fabrication technology

Scattering of elastic waves by a cylindrical cavity in a solid

Timothy S. Lewis, David W. Kraft, and Norbert Hom

J. Appl. Phys. 47, 1795 (1976); http://dx.doi.org/10.1063/1.322894 (4 pages) | Cited 8 times

Online Publication Date: 28 August 2008

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Numerical computations of scattering cross sections are made for plane compressional and shear waves incident normally upon an infinitely long circular cylindrical cavity in a homogeneous isotropic elastic solid. Dependencies of the cross sections upon the variables ka and κa (k and κ are the compressional and shear wave vector amplitudes, respectively, and a is the cylinder radius) and upon the material parameter κ/k are discussed, along with the relative contributions of the various components of the total cross sections. Computations are made over the range 0⩽ka⩽6 for incident compressional waves, and 0⩽κa⩽10 for incident shear waves. Both sets of computations are done for a number of values of κ/k corresponding to various host materials.
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62.30.+d Mechanical and elastic waves; vibrations
41.20.Jb Electromagnetic wave propagation; radiowave propagation

Integral formalism for surface waves in piezoelectric crystals. Existence considerations

J. Lothe and D. M. Barnett

J. Appl. Phys. 47, 1799 (1976); http://dx.doi.org/10.1063/1.322895 (9 pages) | Cited 61 times

Online Publication Date: 28 August 2008

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An integral formalism for surface waves in piezoelectric half‐infinite solids valid up to the critical velocity is developed. Various boundary conditions are considered and, in particular, the problem of which boundary conditions allow surface‐wave solutions for velocities below the limiting velocity vL is discussed in detail. It is proved that (a) with a mechanically free surface and zero dielectric constant for adjoining medium, at most one solution is possible for v<vL, (b) with a mechanically clamped surface and zero dielectric constant for adjoining medium, no solution is possible for v<vL, (c) with a mechanically clamped surface and an infinitely conducting adjoining medium, no solution is possible for v<vL, and (d) with a mechanically free surface and an infinitely conducting adjoining medium, at least one and at most two solutions are possible for v<vL. When two solutions are possible, one solution is of the Bluestein‐Gulyaev type.
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41.20.Jb Electromagnetic wave propagation; radiowave propagation
68.35.Ja Surface and interface dynamics and vibrations
77.65.-j Piezoelectricity and electromechanical effects

Dielectric breakdown of Ag2S in the Au‐Ag2S‐Ag system

S. P. Sharma and J. H. Thomas III

J. Appl. Phys. 47, 1808 (1976); http://dx.doi.org/10.1063/1.322896 (4 pages) | Cited 5 times

Online Publication Date: 28 August 2008

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Electrical breakdown of tarnish films (Ag2S) on silver has been investigated in the Au‐Ag2S‐Ag system. Dielectric breakdown in the Au‐Ag2S‐Ag system is polarity sensitive and depends on the rate of application of voltage to the film. Breakdown is consistent with multiple electron avalanche processes. Data indicate intrinsic breakdown fields greater than 3×105 V/cm (for fast rise time voltages). For slow rise time voltages, breakdown is strongly affected by silver ion mobility and becomes polarity dependent. The conductivity ratio (σAgrich/σSrich) has been obtained as a function of time and the average Ag ion mobility (2×10−8 cm2/V sec) has been determined.
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73.40.Jn Metal-to-metal contacts
73.61.Cw Elemental semiconductors
73.61.Ey III-V semiconductors
73.61.Ga II-VI semiconductors
73.61.Jc Amorphous semiconductors; glasses
73.61.Le Other inorganic semiconductors
77.22.Jp Dielectric breakdown and space-charge effects
66.30.J- Diffusion of impurities

Modeling of enhanced diffusion under ion irradiation

S. M. Myers, D. E. Amos, and D. K. Brice

J. Appl. Phys. 47, 1812 (1976); http://dx.doi.org/10.1063/1.322897 (8 pages) | Cited 41 times

Online Publication Date: 28 August 2008

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The differential equations which govern enhanced diffusion under ion irradiation are solved using recently developed numerical techniques. Accurate time‐dependent profiles for vacancies, interstitials, and diffusing atoms are generated thereby with minimal computer time. The theoretical description is improved further by incorporating refined calculations of the atomic displacement rate by energetic ions. Three representative cases of enhanced diffusion are treated in detail: Al diffusion in Al under 100‐keV Al irradiation, Al diffusion in Al under uniform irradiation, and W diffusion in W under 100‐keV proton irradiation. It is shown that more information may be obtained from the diffused atomic profiles if the irradiation damage rate varies with depth in a known way over the diffusion region. Under this condition, both the shape and the time dependence of the atomic profile are sensitive to the rate coefficient for point‐defect annihilation. When the annihilation coefficient is so determined, the point‐defect creation rate can be uniquely related to the enhanced atomic diffusion coefficient. Under irradiation with a limited range, the atomic profiles typically pass through a complicated form, but ultimately reach a flat shape with a relatively abrupt drop‐off at greater depths. This end condition is qualitatively independent of the detailed structure of the irradiation profile, but the sharpness of the drop‐off is a function of the rate coefficient for point‐defect annihilation.
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61.72.U- Doping and impurity implantation
66.30.J- Diffusion of impurities
61.72.jd Vacancies
61.72.jj Interstitials

Light scattering from smectic liquid‐crystal waveguides

T. G. Giallorenzi, J. A. Weiss, and J. P. Sheridan

J. Appl. Phys. 47, 1820 (1976); http://dx.doi.org/10.1063/1.322898 (7 pages) | Cited 11 times

Online Publication Date: 28 August 2008

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Light scattering properties of smectic‐A liquid‐crystal thin‐film waveguides are studied both theoretically and experimentally. A Green’s function analysis of the depolarized light scattering induced by thermal fluctuations in the average molecular alignment is presented. Scattered power distributions and scattering coefficients for mode conversion and for scattering out of the guide are derived. It is shown that the power distributions for scattering from nematic and smectic waveguides differ greatly and that scattering losses in smectic‐A liquid‐crystal waveguides are several orders of magnitude lower than those encountered in nematic guides. Power loss in these waveguides, due to light scattering arising from thermally induced dynamical distortions of the smectic planes, is calculated to be on the order of 2 dB/cm and is experimentally verified.
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42.79.Gn Optical waveguides and couplers
81.05.-t Specific materials: fabrication, treatment, testing, and analysis
78.20.-e Optical properties of bulk materials and thin films

Phase transition in NaNO3

E. R. Johnson, A. Frances, and C. Cm. Wu

J. Appl. Phys. 47, 1827 (1976); http://dx.doi.org/10.1063/1.322899 (2 pages) | Cited 5 times

Online Publication Date: 28 August 2008

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A new phase transition occurring in NaNO3 at about 260 °K in both cooling and heating cycles is reported. The transition is associated with an expansion of the lattice resulting in approximately a 3.6% decrease in the density.
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64.70.K- Solid-solid transitions
65.40.De Thermal expansion; thermomechanical effects
61.05.C- X-ray diffraction and scattering

Tunneling characteristics of thin epitaxial Bi‐film–SiO2–Pb junctions

Hajime Asahi and Akira Kinbara

J. Appl. Phys. 47, 1829 (1976); http://dx.doi.org/10.1063/1.322900 (4 pages) | Cited 1 time

Online Publication Date: 28 August 2008

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The tunneling characteristics in thin epitaxial Bi films (thickness: 400–1200 Å) were investigated. Bi‐SiO2‐Pb tunnel junctions were prepared by vacuum deposition onto freshly cleaved mica substrates in an ultrahigh vacuum system. The dI/dV‐V curve has a large peak at the Bi positive voltage range (150–250 mV) which can be attributed to the band structure of Bi. In the low voltage range (‖V‖<25 mV), d2I/dV2‐V curves show the peaks or dips reflecting the state density of superconducting lead. The phonon‐assisted tunneling peaks or dips in the normal state were also observed. For medium voltage range (‖V‖≳25 mV), there are several peaks or dips due to phonons of SiO2. The subband edges generated by quantum size effects were not observed, probably because the electron bands and the hole band of Bi overlap each other, located at the L and T points in the Brillouin zone, respectively.
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73.40.Gk Tunneling
74.50.+r Tunneling phenomena; Josephson effects
74.78.-w Superconducting films and low-dimensional structures
73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)

Cracks and energy—Criteria for brittle fracture

R. H. Doremus

J. Appl. Phys. 47, 1833 (1976); http://dx.doi.org/10.1063/1.322901 (4 pages) | Cited 14 times

Online Publication Date: 28 August 2008

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The energies of cracks are considered in terms of the first and second laws of thermodynamics, and it is concluded that the Griffith criterion provides a necessary but not sufficient condition for crack propagation. Fracture occurs only when the crack tip radius is larger than a critical value that is several times the interatomic spacing. Surface energies calculated from fracture experiments probably give only an upper bound to the true surface energies of solids. The radius of the crack tip is a parameter that cannot be ignored in fracture experiments.
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46.50.+a Fracture mechanics, fatigue and cracks
62.20.M- Structural failure of materials
81.90.+c Other topics in materials science (restricted to new topics in section 81)

Computer simulation of x‐ray diffraction topographs of stacking faults

B. C. Wonsiewicz and J. R. Patel

J. Appl. Phys. 47, 1837 (1976); http://dx.doi.org/10.1063/1.322902 (9 pages) | Cited 4 times

Online Publication Date: 28 August 2008

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A group of programs are described which will simulate a photograph of arbitrary contrast ratio or exposure. We have used these programs to simulate x‐ray topographs of stacking faults as described by Authier’s spherical wave treatment of a perfect crystal with a stacking fault. Intrinsic and extrinsic faults are examined with a range of different wavelengths, fault orientations, diffraction conditions, specimen thicknesses, and absorption coefficients. In cases where experimental topographs are available, they correspond closely to the simulations, thereby indicating the basic correctness of Authier’s theory. The simulations illustrate the separation of the complex diffraction pattern into three components. Only one component carries information on the nature of the fault. The simulations clearly delineate the conditions for identifying the fault type; namely, the critical value of μd for adequate visibility of the I3 fringes is in the range 1<μd<2. Traverse patterns are demonstrated to be an unreliable guide to the nature of the fault.
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61.72.Nn Stacking faults and other planar or extended defects
61.05.C- X-ray diffraction and scattering

Some aspects of the performance of refrigerating thermojunctions with radial flow of current

K. Landecker

J. Appl. Phys. 47, 1846 (1976); http://dx.doi.org/10.1063/1.322903 (6 pages) | Cited 4 times

Online Publication Date: 28 August 2008

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An expression for the maximum temperature difference ΔTmax produced between the hot and cold junctions of a thermocouple is derived when the arms are disks of thermoelectric material. In these disks the flow of current is in a direction radially inwards or radially outwards. No assumptions have been made about the distribution of the Joule heat over the hot and cold junctions. The solution as a function of the ratio (ro/ri) of the outer to inner radii of the N and P disks constituting the couple exhibits an interesting singularity at one particular value of this ratio. If ro/ri approaches the numerical value 4.5, the maximum temperature difference ΔTmax appears to have no limit. However, its growth is finally arrested by the temperature dependence of the figure of merit Z. It is then found experimentally that the current through the junction may be increased to large values without causing ΔT to pass through a maximum. The coefficient of performance tends to unity at the critical ratio ro/ri=4.5. Finally, it is pointed out that junctions whose arms are in the form of rotationally symmetrical bodies with lateral surfaces generated by hyperbolae are a more perfect approach to the mathematical model adopted than are flat disks. Such junctions produced temperatures lower than junctions with arms of any other shape.
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07.20.-n Thermal instruments and apparatus
85.80.Fi Thermoelectric devices
72.15.Jf Thermoelectric and thermomagnetic effects

Photoelectronic properties of high‐resistivity GaAs : O

Alice L. Lin, Eric Omelianovski, and Richard H. Bube

J. Appl. Phys. 47, 1852 (1976); http://dx.doi.org/10.1063/1.322904 (7 pages) | Cited 126 times

Online Publication Date: 28 August 2008

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The photoelectronic properties of high‐resistivity n‐type GaAs : O have been investigated through measurements of dark conductivity and Hall effect, optical absorption, photoconductivity, and photo‐Hall effect as a function of photon energy, light intensity and temperature, optical quenching of photoconductivity, and thermally stimulated conductivity. The results of all measurements can be described consistently by a four‐level model (0.5, 0.7, 1.0, and 1.25 eV below the conduction band edge) plus eight electron trapping states (with depth between 0.15 and 0.54 eV) common to many different types of high‐resistivity GaAs. At 82 °K, illumination with photons of energy between 1.0 and 1.25 eV produces a major shift in the photoconductivity toward p type and a persistent quenching of n‐type photoconductivity that recovers abruptly only upon warming above 105 °K. Low‐frequency photocurrent oscillations are associated with the 1.25‐eV level. The capture cross section of five of the electron trapping states is small [(5–8) ×10−19 cm2)] and decreases with electric field.
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78.40.Fy Semiconductors
72.40.+w Photoconduction and photovoltaic effects
72.80.Ey III-V and II-VI semiconductors

Photoelectronic properties of high‐resistivity GaAs : Cr

Alice L. Lin and Richard H. Bube

J. Appl. Phys. 47, 1859 (1976); http://dx.doi.org/10.1063/1.322905 (9 pages) | Cited 70 times

Online Publication Date: 28 August 2008

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The photoelectronic properties of high‐resistivity n‐type GaAs : Cr are quite similar to those of high‐resistivity n‐type GaAs : O described in the preceding paper. In the low‐temperature region, intrinsic photoconductivity is n type, increases exponentially with 1/T, and can be consistently described by a simple one‐level Shockley‐Read recombination model with a level lying 0.66 eV below the conduction band and a density that is remarkably constant over a variety of different materials. Two levels characteristic of the Cr doping lie at 0.86 eV below the conduction band and at 0.9 eV above the valence band. Low‐frequency photocurrent oscillations are associated with levels at 0.86 and 1.25 eV below the conduction band. The extrinsic photoconductivity at 0.86 eV is produced via two steps: (i) electrons are photoexcited from the ground state to the excited state of Cr+2 (d4) center, and (ii) they are then thermally excited to the conduction band.
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78.40.Fy Semiconductors
72.40.+w Photoconduction and photovoltaic effects
72.80.Ey III-V and II-VI semiconductors

Effects of inhomogeneities on the parametric excitation of the upper‐hybrid resonance

V. S. Chan and S. R. Seshadri

J. Appl. Phys. 47, 1868 (1976); http://dx.doi.org/10.1063/1.322906 (6 pages) | Cited 3 times

Online Publication Date: 28 August 2008

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The effects of the inhomogeneities of the number density and the magnitude of the magnetostatic field on the characteristics of the parametrically excited instability of the extraordinary mode near the upper‐hybrid resonant frequency are investigated for the case in which the pump wave and the backscattered idler wave are both ordinary modes. The three interacting waves propagate parallel to a given direction perpendicular to the magnetostatic field whose direction remains unchanged throughout the warm plasma of infinite extent. The parametrically excited instability of the upper‐hybrid wave is of the convective or the absolute type according to whether the effective wave number has a linear or a quadratic profile. For both types of instabilities, there are two threshold values for the amplitude of the pump field and they correspond to the requirements for overcoming the damping losses and the convective losses. Numerical results for the various threshold amplitudes are presented as functions of the strength of the magnetostatic field. The inhomogeneities generally increase the various threshold amplitudes as compared to the case of a homogeneous plasma.
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52.35.Py Macroinstabilities (hydromagnetic, e.g., kink, fire-hose, mirror, ballooning, tearing, trapped-particle, flute, Rayleigh-Taylor, etc.)
52.40.Db Electromagnetic (nonlaser) radiation interactions with plasma

Self‐interaction of the upper hybrid wave

V. S. Chan and S. R. Seshadri

J. Appl. Phys. 47, 1874 (1976); http://dx.doi.org/10.1063/1.322882 (6 pages) | Cited 1 time

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The self‐interaction of the extraordinary mode propagating across the magnetostatic field in an electron plasma is investigated with particular attention to the range of frequencies close to the upper hybrid resonant frequency. The slowly varying amplitude of the upper hybrid wave satisfies a cubic Schrödinger equation which is deduced using the method of Kakutani and Sugimoto. The analysis of the Schrödinger equation shows that the extraordinary mode, in the neighborhood of the upper hybrid resonant frequency, is modulationally stable or unstable according to whether the wave number is below or above a critical value which is controlled only by the dispersive properties of the wave and which corresponds to frequencies slightly below the upper hybrid resonant frequency.
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52.35.Mw Nonlinear phenomena: waves, wave propagation, and other interactions (including parametric effects, mode coupling, ponderomotive effects, etc.)
52.40.Db Electromagnetic (nonlaser) radiation interactions with plasma

Relationship between single‐crystal and polycrystal electrical conductivity

Kalman Schulgasser

J. Appl. Phys. 47, 1880 (1976); http://dx.doi.org/10.1063/1.322907 (7 pages) | Cited 27 times

Online Publication Date: 28 August 2008

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The problem of the prediction of the effective electrical conductivity of a polycrystal from the electrical conductivity of a single crystal is considered. It is shown that the familiar Voigt‐Reuss bounds on the behavior of a polycrystal are the very best generally valid bounds that have thus far been proposed and that the various methods that are claimed to predict exact effective conductivity (or narrow bounds) all include implicit restrictions on the internal geometry of the polycrystal. This is accomplished by constructing a series of statistically homogeneous and isotropic polycrystal models for which the effective conductivity can be exactly calculated. It is hence to be expected that no universal relationship between single‐crystal and polycrystal conductivity exists. Experimental evidence is adduced to support this conclusion. The results are also applicable to the analogous problems of thermal conductivity and electrical permittivity.
Show PACS
72.10.Bg General formulation of transport theory
77.22.Ch Permittivity (dielectric function)
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