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1 Feb 1999

Volume 85, Issue 3, pp. 1249-2009

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A reciprocal theorem for effective conductivities of two-dimensional composites containing multiply coated cylinders of arbitrary cross section

Shih-Yuan Lu

J. Appl. Phys. 85, 1975 (1999); http://dx.doi.org/10.1063/1.369189 (3 pages)

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A reciprocal theorem for the effective conductivities of two-dimensional (2D) rectangular arrays of multiply coated cylinders of arbitrary cross section is derived. The theorem is expressed as: σeffx(σ0,σ1,σ2,…,σn,1)×σeffy(1/σ0,1/σ1,1/σ2,…,1/σn,1) = 1, where σeffx and σeffy are the reduced effective conductivities of the array in the x and y directions, respectively, and σ0 and σi (i = 1,n) are the reduced conductivities of the cylinder and coating layer i, respectively, with the matrix assigned the reduced conductivity of one. This theorem is also valid for a class of 2D composites containing aligned, randomly distributed, multiply coated cylinders of arbitrary cross section, whose heat conduction behavior can be described by an equivalent inclusion model. © 1999 American Institute of Physics.
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44.10.+i Heat conduction

Simple formula for the switching field of ultrathin small magnetic structures

S. T. Chui and V. N. Ryzhov

J. Appl. Phys. 85, 1978 (1999); http://dx.doi.org/10.1063/1.369190 (3 pages) | Cited 1 time

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Mechanisms for the switching of the magnetization in small structures are summarized. We derive an analytic formula for the switching field in terms of the system variables and test it against results from Monte Carlo simulations. © 1999 American Institute of Physics.  
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75.70.Ak Magnetic properties of monolayers and thin films
75.70.Kw Domain structure (including magnetic bubbles and vortices)
75.40.Mg Numerical simulation studies

Analytical description of “athermal” nucleation and its relevance to rapidly quenched fluids

Vitaly A. Shneidman

J. Appl. Phys. 85, 1981 (1999); http://dx.doi.org/10.1063/1.369191 (3 pages) | Cited 2 times

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Results of a matched asymptotic analysis of the nucleation equation are used to obtain the “athermal” flux due to variation of the critical size. The total critical flux is also evaluated. Results, which also include estimations of crystallization rates, are used to refine the nucleation-mechanism diagram for liquid silicon proposed by J. S. Im, Gupta, and Crowder [V. V. Gupta, and M. A. Crowder, Appl. Phys. Lett. 72, 662 (1998)]. The possibility of experimental detection of athermal effects on the background of other effects of time-dependent nucleation is discussed. © 1999 American Institute of Physics.
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64.60.Q- Nucleation
64.70.D- Solid-liquid transitions

Electrostatic Aharonov–Bohm effect in solids revised

T. Figielski and T. Wosiński

J. Appl. Phys. 85, 1984 (1999); http://dx.doi.org/10.1063/1.369192 (3 pages) | Cited 4 times

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We consider the Aharonov–Bohm [Phys. Rev. 115, 485 (1959)] interferometer (or a hypothetical quantum interference transistor) that consists of a single-channel quantum wire split into a mesoscopic loop, whose conductance is controlled by a voltage applied between a gate electrode coupled capacitively to one branch of the loop and the wire. It is deduced from fundamental properties of one-dimensional conductors that putting a single elementary charge on the gate–wire capacitor dramatically alters the interference conditions in the device by introducing the phase shift π/2. This surprising result means that the electrostatic Aharonov–Bohm effect belongs in fact to the category of single-electron phenomena in solids and that inherent charge fluctuations can make its clear observation impossible. © 1999 American Institute of Physics.
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85.35.Gv Single electron devices
85.35.Ds Quantum interference devices
85.30.De Semiconductor-device characterization, design, and modeling

Photoacoustic study of the effect of hydroxyl ion on thermal diffusivity of γ alumina

S. Sankara Raman, V. P. N. Nampoori, C. P. G. Vallabhan, G. Ambadas, and S. Sugunan

J. Appl. Phys. 85, 1987 (1999); http://dx.doi.org/10.1063/1.369193 (2 pages)

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The effect of the chemisorbed hydroxyl groups on the thermal diffusivity of γ alumina is determined by evaluating the thermal diffusivity at various degassing temperatures and by doping it with rare earth oxide using photoacoustic technique. The thermal diffusivity is found to decrease with the increase in degassing temperature as well as with the increase in the doping concentration of rare earth oxide. This decrease has been attributed to the loss of hydroxyl ion from the γ-Al2O3. © 1999 American Institute of Physics.
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66.70.-f Nonelectronic thermal conduction and heat-pulse propagation in solids; thermal waves
68.03.Fg Evaporation and condensation of liquids
68.43.Mn Adsorption kinetics
43.35.Ud Thermoacoustics, high temperature acoustics, photoacoustic effect
78.20.hb Piezo-optical, elasto-optical, acousto-optical, and photoelastic effects

Spontaneous emission from InAs/GaSb quantum wells grown by molecular beam epitaxy

N. Bertru, A. N. Baranov, Y. Cuminal, G. Boissier, C. Alibert, A. Joullie, and B. Lambert

J. Appl. Phys. 85, 1989 (1999); http://dx.doi.org/10.1063/1.369175 (3 pages) | Cited 6 times

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We have investigated the spontaneous emission from InAs/GaSb quantum wells grown by molecular beam epitaxy. A strong photoluminescence signal was observed only from samples grown in a narrow substrate temperature range around 400 °C with InSb-like interfaces. From an analysis of the photoluminescence energy with the excitation density, we demonstrated the formation of triangular quantum wells for holes in the GaSb barriers close to the interfaces. Finally, the temperature dependence of the photoluminescence peak energy showed a deviation from the InAs band gap evolution at low temperature, which could be related to the type II broken gap band alignment. © 1999 American Institute of Physics.
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78.66.Fd III-V semiconductors
78.55.Cr III-V semiconductors
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
81.05.Ea III-V semiconductors
73.20.At Surface states, band structure, electron density of states

Cathodic arc carbon plasma/gas interaction in fullerenes synthesis study

J.-L. Meunier

J. Appl. Phys. 85, 1992 (1999); http://dx.doi.org/10.1063/1.369194 (3 pages) | Cited 3 times

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Cathodic arc plasmas show characteristics similar to the fullerene producing laser ablation plasmas. Experimental and theoretical results on cathodic arc systems are applied to study the possible zones of formation of the large carbon molecules. These are believed to form in a relatively localized region whose position is governed by basic gas and expanding plasma parameters. A snowplow plasma expansion model gives a probable zone for the nucleation of larger carbon molecule located at 3 mm from the cathode for a 120 A arc in 55 Torr of helium. This correlates with preliminary spectroscopic measurements of C2 molecular radiation emission observed in pulsed cathodic arc plasma discharges in helium. © 1999 American Institute of Physics.
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52.77.Bn Etching and cleaning
52.77.Dq Plasma-based ion implantation and deposition
81.20.-n Methods of materials synthesis and materials processing
61.48.-c Structure of fullerenes and related hollow and planar molecular structures

Reciprocal space mapping of phase transformation in epitaxial PbTiO3 thin films using synchrotron x-ray diffraction

K. S. Lee and S. Baik

J. Appl. Phys. 85, 1995 (1999); http://dx.doi.org/10.1063/1.369195 (3 pages) | Cited 21 times

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Phase transformation in epitaxial PbTiO3 thin films grown on MgO(001) substrates was studied and quantified by two-dimensional reciprocal space mapping technique using synchrotron x-ray diffraction equipped with an in situ high temperature stage. Just below the Curie temperature, a twin-like domain structure was formed with an initial value of c-domain abundance, α ∼ 0.3, and the value increased continuously during cooling, and eventually the c-domain dominant structure (α ∼ 0.72) was achieved at room temperature through continuous expansion of the c domains. By investigating the intensity distribution of contour maps, domain tilting and mosaicity were characterized along the q[h00] direction and the presence of a strain gradient along the growth direction q[001] was also confirmed from the asymmetric distribution of the contour maps. © 1999 American Institute of Physics.
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77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
77.80.B- Phase transitions and Curie point
77.55.-g Dielectric thin films
77.80.Dj Domain structure; hysteresis
68.55.Nq Composition and phase identification
64.70.K- Solid-solid transitions

Pressure sensing with a flexural plate wave resonator

M. A. Butler, M. K. Hill, J. J. Spates, and S. J. Martin

J. Appl. Phys. 85, 1998 (1999); http://dx.doi.org/10.1063/1.369196 (3 pages)

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A silicon nitride membrane supported on a silicon substrate and having a sealed air cavity underneath has been used as a pressure sensor. Membrane resonances are excited and detected using conductor lines patterned on the membrane in combination with an applied magnetic field. The resonant frequency depends strongly upon membrane tension and thus the differential pressure across the membrane. © 1999 American Institute of Physics.  
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07.07.Df Sensors (chemical, optical, electrical, movement, gas, etc.); remote sensing
46.40.Cd Mechanical wave propagation (including diffraction, scattering, and dispersion)
62.30.+d Mechanical and elastic waves; vibrations

Theoretical evidence for the semi-insulating character of AlN

Antonella Fara, Fabio Bernardini, and Vincenzo Fiorentini

J. Appl. Phys. 85, 2001 (1999); http://dx.doi.org/10.1063/1.369197 (3 pages) | Cited 28 times

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We present ab initio density-functional calculations for acceptors, donors, and native defects in aluminum nitride, showing that acceptors are deeper (Be∼0.25 eV, Mg∼0.45 eV) and less soluble than in GaN; at further variance with GaN, both the extrinsic donors SiAl and CAl, and the native donor VN (the anion vacancy) are found to be deep (about 1 to 3 eV below the conduction). We thus predict that doped AlN will generally turn out to be semi-insulating in the normally achieved Al-rich conditions, in agreement with the known doping difficulties of high-x AlxGa1−xN alloys. © 1999 American Institute of Physics.
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71.55.Eq III-V semiconductors
71.15.Mb Density functional theory, local density approximation, gradient and other corrections

Step structure of arsenic-terminated vicinal Ge (100)

S. Gan, L. Li, M. J. Begarney, D. Law, B.-K. Han, and R. F. Hicks

J. Appl. Phys. 85, 2004 (1999); http://dx.doi.org/10.1063/1.369176 (3 pages)

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Germanium (100) crystals, 9° off-axis towards the [011] were exposed to 2.0 Torr of tertiarybutylarsine and 99.0 Torr of hydrogen at 650 °C, then heated to between 450 and 600 °C in vacuum or H2. The resulting surfaces consist of narrow dimer-terminated terraces, with (1×2) and (2×1) domains, that are separated by steps between one and eight atomic layers in height. The distribution of (1×2) and (2×1) domains changes with temperature, exhibiting a pronounced maximum in the (1×2) fraction at 510 °C. These results suggest that the arsenic passivation of germanium is a critical step in gallium arsenide heteroepitaxy. © 1999 American Institute of Physics.
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68.35.B- Structure of clean surfaces (and surface reconstruction)
81.05.Cy Elemental semiconductors
81.65.Rv Passivation

Multibarrier heterostructure GaAs/AlAs switch

A. Reklaitis

J. Appl. Phys. 85, 2007 (1999); http://dx.doi.org/10.1063/1.369180 (3 pages)

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A multibarrier heterostructure GaAs/AlAs current switching diode has been proposed and investigated by Monte Carlo particle simulations. The switching phenomenon is based on electron tunneling and thermoemission from the GaAs wells to the AlAs barriers, electron drift across the thin AlAs barriers followed by a subsequent impact ionization in the undoped GaAs layers. The calculated switching voltage is close to 100 V for the diode involving four AlAs barriers at 300 K lattice temperature. The estimated switching time is in the order of 10 ps. © 1999 American Institute of Physics.
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85.30.Mn Junction breakdown and tunneling devices (including resonance tunneling devices)
85.30.De Semiconductor-device characterization, design, and modeling
73.50.Fq High-field and nonlinear effects
73.61.Ey III-V semiconductors
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