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15 Jan 1999

Volume 85, Issue 2, pp. 641-1243

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Simple thermodynamic diagrams for real refrigeration systems

J. M. Gordon, K. C. Ng, and H. T. Chua

J. Appl. Phys. 85, 641 (1999); http://dx.doi.org/10.1063/1.369247 (6 pages) | Cited 3 times

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The thermodynamic performance of real irreversible cooling and refrigeration systems (chillers) can be summarized in simple rectangular temperature-entropy diagrams, in analogy to classic pedagogical examples for idealized reversible devices. The key to translating complex dissipative losses into this graphical framework is the process average temperature—a factor that can be calculated from nonintrusive experimental measurements, for converting entropy production into lost work. An uncomplicated thermodynamic model is used to transform the governing chiller performance equations into an easily-interpreted graph. Examples based upon actual data from commercial work-driven (reciprocating) and heat-driven (absorption) chillers are presented, and are used to highlight the predominance of internal dissipation in determining chiller efficiency. With the thermodynamic diagram representation, the relative roles of each irreversibility source, as well as the reversible and endoreversible limits, become transparent. © 1999 American Institute of Physics.
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07.20.Mc Cryogenics; refrigerators, low-temperature detectors, and other low-temperature equipment
05.70.Ln Nonequilibrium and irreversible thermodynamics

Signals induced in semiconductor gamma-ray imaging detectors

J. D. Eskin, H. H. Barrett, and H. B. Barber

J. Appl. Phys. 85, 647 (1999); http://dx.doi.org/10.1063/1.369198 (13 pages) | Cited 34 times

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The signal induced in a readout circuit connected to a pixel electrode in a semiconductor gamma-ray imaging array is calculated by solving the Laplace equation. Two approaches are presented that use Green functions in solving the boundary value problem: decomposition into basis functions, and construction of an infinite series of image charges. Another approach is developed based on the Ramo–Shockley theorem, which makes use of weighting potentials. These potentials may be readily calculated in three dimensions using a Fourier-transform propagation technique. An analytic solution is found for the special two-dimensional case of a strip detector. Experiments on CdZnTe square-pixel test structures using alpha radiation confirm the expected trends in pulse shape as a function of pixel size. Signals observed simultaneously on adjacent pixels also follow the predicted division of currents. Trends with pixel size are also confirmed in the shape of pulse-height spectra taken using a 99mTc source. © 1999 American Institute of Physics.
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29.40.Wk Solid-state detectors
07.68.+m Photography, photographic instruments; xerography
02.30.Jr Partial differential equations
07.85.Fv X- and γ-ray sources, mirrors, gratings, and detectors
02.10.Ud Linear algebra
02.10.Xm Multilinear algebra
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Capture radius of magnetic particles in random cylindrical matrices in high gradient magnetic separation

Mayuree Natenapit and Wirat Sanglek

J. Appl. Phys. 85, 660 (1999); http://dx.doi.org/10.1063/1.369199 (5 pages) | Cited 7 times

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An effective medium treatment (EMT) was used to model the magnetic field around randomly distributed magnetic cylindrical fine wires and applied to calculate the capture radius of paramagnetic particles in a filter operating either in the longitudinal or transverse design mode. This article reports capture radius as a function of the ratio of magnetic velocity to fluid entrance velocity with a magnetic parameter which determines the strength of the magnetic short-range force, as a parameter. Finally, comparisons of the results based on the EMT approach, with those obtained by using the single-wire model, are given along with discussion on the criteria for validity of the simple single-wire model. © 1999 American Institute of Physics.
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75.50.Tt Fine-particle systems; nanocrystalline materials
85.70.-w Magnetic devices
75.20.-g Diamagnetism, paramagnetism, and superparamagnetism
07.55.-w Magnetic instruments and components
41.20.Gz Magnetostatics; magnetic shielding, magnetic induction, boundary-value problems

Relaxation kinetics in quantum cascade lasers

S. Slivken, V. I. Litvinov, M. Razeghi, and J. R. Meyer

J. Appl. Phys. 85, 665 (1999); http://dx.doi.org/10.1063/1.369200 (7 pages) | Cited 11 times

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Relaxation kinetics in a quantum cascade intersubband laser are investigated. Distribution functions and gain spectra of a three-subband double-quantum-well active region are obtained as a function of temperature and injection current. The potentially important role of the nonequilibrium phonons at lasing threshold is shown and discussed in details. It is shown that the threshold current is strongly dependent of the power dissipated in the active region in steady state. The numerical calculations for an 8.5 μm laser illustrate the general issues of relaxation kinetics in quantum cascade lasers. Temperature dependence of the threshold current is obtained in a good agreement with the experiments. © 1999 American Institute of Physics.
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42.55.Px Semiconductor lasers; laser diodes

Optimization of double pulse pumping for Ni-like Sm x-ray lasers

J. Y. Lin, G. J. Tallents, R. Smith, A. G. MacPhee, E. Wolfrum, J. Zhang, G. Eker, R. Keenan, C. L. S. Lewis, D. Neely, R. M. N. O’Rourke, G. J. Pert, S. J. Pestehe, and J. S. Wark

J. Appl. Phys. 85, 672 (1999); http://dx.doi.org/10.1063/1.369201 (4 pages) | Cited 11 times

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We report a systematic study of double pulse pumping of the Ni-like Sm x-ray laser at 73 Å, currently the shortest wavelength saturated x-ray laser. It is found that the Sm x-ray laser output can change by orders of magnitude when the intensity ratio of the pumping pulses and their relative delay are varied. Optimum pumping conditions are found and interpreted in terms of a simple model. © 1999 American Institute of Physics.
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42.55.Vc X- and γ-ray lasers
42.65.Re Ultrafast processes; optical pulse generation and pulse compression

Higher-order optical nonlinearity observed in host–guest liquid crystals

Hiroshi Ono and Yoshiro Harato

J. Appl. Phys. 85, 676 (1999); http://dx.doi.org/10.1063/1.369202 (5 pages) | Cited 11 times

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Optical nonlinearity in host–guest liquid crystals was characterized by systematically investigating both the experimental diffraction beam pattern and the theoretical one originating in photothermal self-phase modulation. The experimental diffraction patterns were in very good agreement with the calculated results when the refractive index changes (Δn) were assumed to be described by the equation Δn = n2I+n4I2, where n2 and n4 are nonlinear coefficients, and I is the light intensity. These higher-order nonlinear coefficients were strongly dependent on the nematic–isotropic transition temperatures of the host–guest liquid crystals, dye concentration, and sample thickness. © 1999 American Institute of Physics.
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42.70.Df Liquid crystals
42.70.Nq Other nonlinear optical materials; photorefractive and semiconductor materials
42.65.Jx Beam trapping, self-focusing and defocusing; self-phase modulation
78.20.N- Thermo-optic effects
78.20.nb Photothermal effects
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
61.30.Eb Experimental determinations of smectic, nematic, cholesteric, and other structures
64.70.M- Transitions in liquid crystals

Comparison of the temperature dependence of optical poling between guest-host and side-chain polymer films

Gang Xu, Jinhai Si, Xuchun Liu, Q. G. Yang, Peixian Ye, Zhao Li, and Yuquan Shen

J. Appl. Phys. 85, 681 (1999); http://dx.doi.org/10.1063/1.369147 (5 pages) | Cited 14 times

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A comparison of temperature-dependent optical poling between two azopolymers, a side-chain polymer system (disperse red 19-functionalized polyimide polymer) and a guest-host polymer (dispersed red 1-doped polymethyl methacrylate), has been performed at various poling temperatures ranging from 25 to 70 °C. The observed saturation levels of induced second-order nonlinear susceptibility in all cases could be resolved into two components with a faster and a slower decay process after poling, which were respectively attributed to the cis-to-trans isomerization and the loss of induced polar order by orientational diffusion of azo chromophores. The saturation level and its slower decay component were observed to increase with the increase of poling temperature in the side-chain polymer, but to decrease in the guest-host system. The faster decay components were observed to decrease with poling temperature in both the systems. The decay times of the faster component decreased with temperature in the two polymers. The decay times of the slower component in the guest-host polymer, which were much smaller than those in the side-chain polymer, also decreased with temperature. All the observations have been explained physically. © 1999 American Institute of Physics.
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77.22.Ej Polarization and depolarization
42.65.An Optical susceptibility, hyperpolarizability
77.84.Jd Polymers; organic compounds
77.55.-g Dielectric thin films
78.66.Qn Polymers; organic compounds

Observation of downstream energetic electron/ion flow and accompanied high-power microwave radiation during the opening of a submicrosecond plasma opening switch

Ya. E. Krasik, A. Dunaevsky, J. Felsteiner, and J. R. Goyer

J. Appl. Phys. 85, 686 (1999); http://dx.doi.org/10.1063/1.369148 (10 pages) | Cited 3 times

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In this article, results of experimental investigations of high-energy electron beam generation and transportation in the region downstream of a submicrosecond plasma opening switch (POS) (Ipos  ⩽ 35 kA, τ1/4 ≅ 300 ns) are presented. This electron beam is accompanied by collectively accelerated ions having energies several times higher than the electron energies. Experiments were carried out with different loads: short-circuit, high-impedance, and planar electron diode. It is shown that the electron/ion beam appearance in the region downstream of the POS load occurs almost simultaneously with the beginning of the inductive voltage, independently of the type of load. In addition, generation of high-power microwave radiation (fmw  ⩽ 10 GHz, Pmw ⩽ 200 MW) was observed for all types of loads. We believe that the generation of the microwave radiation is related to the injection of a noncomplete charge-neutralized electron beam into the downstream drift region. These results and a qualitative explanation of the generation of the inductive voltage and microwave radiation are discussed. © 1999 American Institute of Physics.
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52.75.Kq Plasma switches (e.g., spark gaps)
07.77.Ka Charged-particle beam sources and detectors
29.25.Bx Electron sources
41.75.Fr Electron and positron beams

Absolute atomic hydrogen densities in a radio frequency discharge measured by two-photon laser induced fluorescence imaging

L. Chérigier, U. Czarnetzki, D. Luggenhölscher, V. Schulz-von der Gathen, and H. F. Döbele

J. Appl. Phys. 85, 696 (1999); http://dx.doi.org/10.1063/1.369149 (7 pages) | Cited 22 times

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Absolute atomic hydrogen densities were measured in the gaseous electronics conference reference cell parallel plate reactor by Doppler-free two-photon absorption laser induced fluorescence spectroscopy (TALIF) at λ=205 nm. The capacitively coupled radio frequency discharge was operated at 13.56 MHz in pure hydrogen under various input power and pressure conditions. The Doppler-free excitation technique with an unfocused laser beam together with imaging the fluorescence radiation by an intensified charge coupled device camera allows instantaneous spatial resolution along the radial direction. Absolute density calibration is obtained with the aid of a flow tube reactor and titration with NO2. The influence of spatial intensity inhomogenities along the laser beam and subsequent fluorescence are corrected by TALIF in xenon. A full mapping of the absolute density distribution between the electrodes was obtained. The detection limit for atomic hydrogen amounts to about 2×1018 m−3. The dissociation degree is of the order of a few percent. © 1999 American Institute of Physics.
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52.70.Kz Optical (ultraviolet, visible, infrared) measurements
52.25.Os Emission, absorption, and scattering of electromagnetic radiation
52.80.Pi High-frequency and RF discharges

Experimental setup and electrical characteristics of an inductively coupled plasma

V. A. Godyak, R. B. Piejak, and B. M. Alexandrovich

J. Appl. Phys. 85, 703 (1999); http://dx.doi.org/10.1063/1.369150 (10 pages) | Cited 38 times

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This article describes an experimental system that has been used to study inductively coupled plasma (ICP). The aim of this effort was to generate an experimental ICP database over a wide range of discharge conditions (power, frequency, and gas pressure) obtained in the same experimental device and using the same diagnostic means. Design of the experimental setup and diagnostics for measurement of ICP external electrical characteristics (coil voltage and current), power dissipated in plasma and radio frequency plasma potential are given here together with experimental results obtained over a wide range of discharge conditions. © 1999 American Institute of Physics.
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52.70.Ds Electric and magnetic measurements
52.25.Fi Transport properties
52.80.Pi High-frequency and RF discharges

Characterization and modeling of the ablation plumes formed by intense-pulsed ion beam impact on solid targets

H. A. Davis, G. P. Johnston, J. C. Olson, D. J. Rej, W. J. Waganaar, C. L. Ruiz, F. A. Schmidlapp, and M. O. Thompson

J. Appl. Phys. 85, 713 (1999); http://dx.doi.org/10.1063/1.369151 (9 pages) | Cited 4 times

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An investigation of the properties of the ablation products from intense-pulsed ion beam impact on solid targets is described. Measurements and calculations of the properties of the ablation plume are presented and correlated with incident beam parameters. Experimental techniques include Thomson parabola particle spectroscopy to measure the incident ion beam atomic composition and the energy spectrum of each beam component, thermal imaging to measure the incident-beam energy density, time-resolved photography to measure the plume expansion time history and geometry, and time-resolved energy-density measurements of the plume. The results of a thermal transport model of the beam-target interaction are presented, and a detailed comparison with measurements is made. © 1999 American Institute of Physics.
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52.40.Mj Particle beam interactions in plasmas
52.50.Dg Plasma sources
52.70.Kz Optical (ultraviolet, visible, infrared) measurements
41.85.Ja Particle beam transport
41.75.Ak Positive-ion beams
81.15.Jj Ion and electron beam-assisted deposition; ion plating
52.25.Os Emission, absorption, and scattering of electromagnetic radiation
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Temperature dependence of the domain wall width in LaAlO3

Jutta Chrosch and Ekhard K. H. Salje

J. Appl. Phys. 85, 722 (1999); http://dx.doi.org/10.1063/1.369152 (6 pages) | Cited 45 times

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Twin wall related diffuse scattering intensities from a single crystal of LaAlO3 were determined using high-resolution x-ray diffraction methods. Rocking curves were measured for sample temperatures between 295 and 900 K. The wall thickness W was determined by comparing the observed diffraction profiles with structure factor calculations for a tanh(x/W) wall profile. It is shown that W ≈ 20 Å at low temperatures and increases slowly with temperature reaching values in excess of 200 Å near Tc ≈ 850 K with W∝∣T−Tc∣−1. © 1999 American Institute of Physics.
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62.20.F- Deformation and plasticity
61.05.cp X-ray diffraction
61.05.cf X-ray scattering (including small-angle scattering)
61.72.Mm Grain and twin boundaries

Half-leaky guided wave determination of azimuthal anchoring energy and twist elastic constant of a homogeneously aligned nematic liquid crystal

F. Yang, J. R. Sambles, and G. W. Bradberry

J. Appl. Phys. 85, 728 (1999); http://dx.doi.org/10.1063/1.369153 (6 pages) | Cited 15 times

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Optical excitation of half-leaky guided modes has been used to explore the director distortion of a homogeneously aligned nematic liquid crystal (BDH E7) under application of an in-plane electric field. Homogeneous alignment is realized by obliquely evaporated SiOx layers with an in-plane field being applied across a 3 mm gap between gold electrodes. The director is initially aligned approximately parallel to the edges of the electrode gap. By modeling the director profile in the cell to fit the half-leaky guided mode reflectivity data, both with and without applied fields, and then comparing the field induced distortions to continuum theory, we obtain both the twist elastic constant k22 and the surface azimuthal anchoring coefficient, Wa. At 23.7 °C we find that k22 = 6.5×10−12 N and Wa = 2.3×10−6 Jm−2. © 1999 American Institute of Physics.
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61.30.Gd Orientational order of liquid crystals; electric and magnetic field effects on order
68.03.Cd Surface tension and related phenomena
78.20.Jq Electro-optical effects
62.10.+s Mechanical properties of liquids
61.30.Cz Molecular and microscopic models and theories of liquid crystal structure

Quantum size and composition effects in photoacoustic spectra of FexZr1−xO2 clusters

F. X. Liu, X. Y. Zhang, Q. Wu, L. Liu, J. Y. Wang, and Q. D. Su

J. Appl. Phys. 85, 734 (1999); http://dx.doi.org/10.1063/1.369248 (5 pages) | Cited 2 times

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The quantum size and composition effects on the optical properties of FexZr1−xO2 (x = 0, 7.5, 15, and 35 wt %, respectively) clusters were studied by measuring their photoacoustic spectra at room temperature. We observed a concomitant smearing of the band gap, narrowing the effective gap of the grains with increasing iron content. These phenomena are attributed partly to the formation of a separate Fe2O3 phase, likely residing at the grain boundaries. The appearance of five spectral bands may be ascribed to the electronic transition of the Fe3+ centers in the samples from the ground level to five excitation states. The exciton peaks occur and shift towards blue, which can be explained by the quantum size effect. The absorption edges exhibit a red shift with increasing Fe content due to the Burstein’s effect. © 1999 American Institute of Physics.
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78.20.hb Piezo-optical, elasto-optical, acousto-optical, and photoelastic effects
78.66.Vs Fine-particle systems
43.35.Ud Thermoacoustics, high temperature acoustics, photoacoustic effect
61.46.-w Structure of nanoscale materials
61.43.Gt Powders, porous materials
73.22.-f Electronic structure of nanoscale materials and related systems
71.35.Cc Intrinsic properties of excitons; optical absorption spectra
78.40.Ha Other nonmetallic inorganics

Use of Rietveld refinement to fit a hexagonal crystal structure in the presence of elastic and plastic anisotropy

M. R. Daymond, M. A. M. Bourke, and R. B. Von Dreele

J. Appl. Phys. 85, 739 (1999); http://dx.doi.org/10.1063/1.369154 (9 pages) | Cited 51 times

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When multiple elastic diffraction peaks are obtained from an x-ray or neutron source, data analysis is commonly performed using a Rietveld refinement applied to the entire pattern, rather than simply performing single peak fits. In the simplest case the crystal structure is assumed to be ideal despite the presence of stresses which, coupled with the elastic and plastic anisotropy of individual grains, can result in a nonisotropic response of the polycrystal. A first step to account for this anisotropy in the refinement is to include an anisotropic strain parameter. In an earlier work [J. Appl. Phys. 82, 1554 (1997)] we included elastic anisotropy into a Rietveld refinement and discussed its validity in the elastic and plastic regimes for a cubic crystal structure. Here we extend the discussion to include anisotropy in hexagonal crystal structures. The agreement between single peak fits and the Rietveld refinement modeled single peak positions is considered for hexagonal close packed beryllium in the presence of an applied compressive load, in both the elastic and plastic regime (to ∼ 1% plastic strain). Agreement is found to be good in the elastic and early plastic regime, where only basal slip is assumed to be active. At higher loads, where prism slip and/or basal fracture are also assumed to be active, agreement is poorer for some diffraction planes. The implications for residual stress measurements are considered. © 1999 American Institute of Physics.
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61.50.Ah Theory of crystal structure, crystal symmetry; calculations and modeling
61.05.cc Theories of x-ray diffraction and scattering
62.20.F- Deformation and plasticity
62.20.D- Elasticity

Search for radiation-induced electrical degradation in ion irradiated sapphire and polycrystalline Al2O3

W. Kesternich

J. Appl. Phys. 85, 748 (1999); http://dx.doi.org/10.1063/1.369155 (5 pages) | Cited 2 times

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An international discussion is being carried out on whether radiation-induced electrical degradation in ceramic insulators does or does not exist. In the present experiments on radiation-induced conductivity and radiation-induced electrical degradation in high purity polycrystalline Al2O3 and sapphire all interfering effects resulting from surface conductances have been eliminated. The results have not confirmed a permanent degradation of the volume conductivity. Radiation-induced conductivity values were observed to decrease with dose. A transient in the electrical conductivity after ion beam off was discovered. © 1999 American Institute of Physics.
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61.80.Jh Ion radiation effects
61.82.Ms Insulators
72.80.Sk Insulators
84.70.+p High-current and high-voltage technology: power systems; power transmission lines and cables

Interaction between Fe, dopants, and secondary defects in MeV Fe ion implanted InP

Andrea Gasparotto, Alberto Carnera, Cesare Frigeri, Francesco Priolo, Beatrice Fraboni, Andrea Camporese, and Gilberto Rossetto

J. Appl. Phys. 85, 753 (1999); http://dx.doi.org/10.1063/1.369156 (8 pages) | Cited 14 times

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We investigate the role of damage production and annealing in determining the Fe redistribution properties when implanting Fe at MeV energies in n-type InP. Fe ion implantation is performed at 2 MeV on (100) InP substrates, both undoped and Sn doped (1.5×1018 cm−3). Implants are performed both at room temperature (RT) and at 200 °C (HT), with doses ranging from 1×1013 to 1.2×1015 cm−2. A double implantation experiment is also performed, coimplanting Fe and P to investigate the influence of the P induced damage on the Fe redistribution/accumulation. Annealing is performed in the temperature range between 650 and 800 °C using flowing phosphine to prevent surface decomposition. To characterize the damage of our samples before and after annealing we employ Rutherford backscattering spectrometry in channeling condition and transmission electron microscopy; Fe depth profiles are measured by secondary ions mass spectrometry. A strict correlation is found between the position of Fe accumulation peaks and that of secondary defects formed in RT implanted samples during annealing; in particular it is shown that end of range dislocation loops and interfaces between damaged and undamaged crystal regions act as gettering sites for Fe atoms. The accumulation process is controlled by Fe diffusion that is greatly enhanced by the presence of mobile point defects related to the implantation damage; on the contrary it is shown that Sn doping has a strong retarding action on Fe diffusion. It is demonstrated that the strong reduction in damage production related to dynamic annealing in HT implantation can be used to reduce or avoid Fe redistribution/accumulation phenomena, leading to fairly stable implantation profiles also for high annealing temperatures and long annealing times. © 1999 American Institute of Physics.
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61.72.uj III-V and II-VI semiconductors
61.80.Jh Ion radiation effects
61.72.Cc Kinetics of defect formation and annealing
61.72.Yx Interaction between different crystal defects; gettering effect
61.82.Fk Semiconductors
61.72.S- Impurities in crystals
61.72.Ff Direct observation of dislocations and other defects (etch pits, decoration, electron microscopy, x-ray topography, etc.)

Two-dimensional simulation of plasma-based ion implantation

M. Paulus, L. Stals, U. Rüde, and B. Rauschenbach

J. Appl. Phys. 85, 761 (1999); http://dx.doi.org/10.1063/1.369157 (6 pages) | Cited 22 times

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A particle-in-cell simulation is used to study the time-dependent evolution of the potential and the electrical field surrounding two-dimensional objects during a high voltage pulse in the context of plasma immersion ion implantation. The numerical procedure is based on the solution of Poisson’s equation on a grid and the determination of the movement of the particles through the grid. Ion current density, implanted concentration, average impact energy, and impact angle of the ions were calculated using this method for two geometrical shapes, a square and an L-shaped object. The nonuniformity of the sheath potential near convex and concave corners is shown. The divergence of the electrical field in the vicinity of corners leads to dramatically reduced concentration of the incident ions. The simulation also shows that a large ion flux hits the surface during the rise time of the pulse. Directly after the rise time, more than 40% of the whole concentration is implanted. Hence, the average impact energy of the ions is reduced during the rise time of the pulse. In the vicinity of corners the incident ions strike the surface under oblique angles. The interior sides of the objects are characterized by smaller average impact angles than the exterior sides. In addition, the dependence of the impact angle and the energy distribution on the pulse time is presented. The influence of the shape of the objects on the average energy of the ions turns out to be slight for both geometries. The results of the particle-in-cell simulation are in good agreement with the published measurements. © 1999 American Institute of Physics.
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85.40.Ry Impurity doping, diffusion and ion implantation technology
52.77.Bn Etching and cleaning
52.77.Dq Plasma-based ion implantation and deposition
52.65.Rr Particle-in-cell method
61.72.up Other materials
61.72.uf Ge and Si
61.72.uj III-V and II-VI semiconductors
79.20.Rf Atomic, molecular, and ion beam impact and interactions with surfaces
52.40.Hf Plasma-material interactions; boundary layer effects

Simulation of dynamic compaction of metal powders

D. Roshan Kumar, R. Krishna Kumar, and P. K. Philip

J. Appl. Phys. 85, 767 (1999); http://dx.doi.org/10.1063/1.369158 (9 pages) | Cited 4 times

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This article presents numerical studies on the deformation of particles during dynamic compaction of metal powders. The analysis of the process is based on a micromechanics approach using multiple particle configurations. The material considered is elastoviscoplastic with interparticle friction. Two-dimensional studies on particles in close packed arrangement were carried out using plane strain conditions for deformation and thermal response. The finite element method using an explicit dynamic analysis procedure was used for the simulations. The influence of speed of compaction, strain hardening, strain rate dependency, interparticle friction and size of the powder particles on the final shape and temperature variations within the particles were analyzed. The studies offer useful information on the shape and temperature variations within the particles. The results provide a better understanding of the dynamic compaction process at the micromechanics level. © 1999 American Institute of Physics.
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81.20.Ev Powder processing: powder metallurgy, compaction, sintering, mechanical alloying, and granulation
81.40.Lm Deformation, plasticity, and creep
81.40.Ef Cold working, work hardening; annealing, post-deformation annealing, quenching, tempering recovery, and crystallization
81.40.Pq Friction, lubrication, and wear
02.70.Dh Finite-element and Galerkin methods
62.20.F- Deformation and plasticity
62.20.Qp Friction, tribology, and hardness
81.05.Bx Metals, semimetals, and alloys

Thermal conductivity of uranium dioxide up to 2900 K from simultaneous measurement of the heat capacity and thermal diffusivity

C. Ronchi, M. Sheindlin, M. Musella, and G. J. Hyland

J. Appl. Phys. 85, 776 (1999); http://dx.doi.org/10.1063/1.369159 (14 pages) | Cited 31 times

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The thermal diffusivity and heat capacity of uranium dioxide have been measured from 500 to 2900 K with an advanced laser-flash technique. These two quantities were determined simultaneously by means of an accurate numerical fitting of the experimental thermograms. At high temperatures the precision of the method used is much better than that associated with conventional laser-flash measurements. It was found that the heat capacity continues to increase even at temperatures above the expected lambda transition (2670 K). The inverse of the thermal diffusivity increases linearly with temperature up to 2600 K, whilst at higher temperatures the slope markedly decreases. A new expression for the thermal conductivity as a function of temperature is proposed, which is corroborated by some theoretical considerations on the underlying heat transport mechanisms. © 1999 American Institute of Physics.
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28.41.Bm Fuel elements, preparation, reloading, and reprocessing
66.70.-f Nonelectronic thermal conduction and heat-pulse propagation in solids; thermal waves
65.40.-b Thermal properties of crystalline solids
65.60.+a Thermal properties of amorphous solids and glasses: heat capacity, thermal expansion, etc.
65.80.-g Thermal properties of small particles, nanocrystals, nanotubes, and other related systems

Effect of strain on the interdiffusion of InGaAs/GaAs heterostructures

W. P. Gillin

J. Appl. Phys. 85, 790 (1999); http://dx.doi.org/10.1063/1.369160 (4 pages) | Cited 7 times

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The results of interdiffusion experiments on two multiple quantum well heterostructures of InGaAs/GaAs are presented. The two samples each had four quantum wells with indium concentrations, in order from the surface, of 5%, 15%, 20%, and 10%. The two samples also had different barrier layer thicknesses to allow any strain or depth dependence of the diffusion to be observed. No effect of strain or depth on the diffusion was observed. © 1999 American Institute of Physics.
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68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties
68.35.Fx Diffusion; interface formation

Temperature dependence of the thermal diffusivity of GaAs in the 100–305 K range measured by the pulsed photothermal displacement technique

M. Soltanolkotabi, G. L. Bennis, and R. Gupta

J. Appl. Phys. 85, 794 (1999); http://dx.doi.org/10.1063/1.369161 (5 pages) | Cited 8 times

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We have measured the variation of the value of the thermal diffusivity of semi-insulating GaAs in the 100–305 K range. The method used is the pulsed photothermal displacement technique. This is a noncontact technique, and the value of the thermal diffusivity is derived from the temporal evolution of the signal rather than its amplitude. This makes the technique less susceptible to uncertainties. We find that the temperature dependence of the thermal conductivity of semi-insulating GaAs follows a power law as T−1.62, in disagreement with results obtained previously. Possible reasons for the deviation within this very important intermediate temperature range are discussed. © 1999 American Institute of Physics.
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66.70.-f Nonelectronic thermal conduction and heat-pulse propagation in solids; thermal waves
65.90.+i Other topics in thermal properties of condensed matter (restricted to new topics in section 65)

Diffusion of Au in ZnSe and its dependence on crystal quality

J. Slotte, R. Salonen, T. Ahlgren, E. Rauhala, J. Keinonen, J. Räisänen, P. Uusimaa, A. Salokatve, M. Pessa, and A. Laakso

J. Appl. Phys. 85, 799 (1999); http://dx.doi.org/10.1063/1.369162 (4 pages) | Cited 1 time

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Diffusion of gold in zinc selenide has been studied by using a 12C and 4He ion backscattering technique. The samples were thin films grown by molecular beam epitaxy on bulk GaAs (100) substrates and on GaAs (100) epitaxial layers followed by evaporation of gold and annealing in the temperature range 400–800 °C. The surface properties of the samples were studied with scanning electron microscopy and atomic force microscopy. The crystal quality of the samples was studied with 4He ion channeling. The gold diffusion was found to depend significantly on the crystal quality of the ZnSe. An empirical model for calculating the diffusion coefficient for different crystal quality ZnSe is presented. © 1999 American Institute of Physics.
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66.30.Ny Chemical interdiffusion; diffusion barriers
68.35.Fx Diffusion; interface formation
68.55.-a Thin film structure and morphology
61.85.+p Channeling phenomena (blocking, energy loss, etc.)
82.80.Yc Rutherford backscattering (RBS), and other methods of chemical analysis
73.40.Ns Metal-nonmetal contacts

Fluorine implantation effect on boron diffusion in Si

Yong-Jik Park and Jong-Jean Kim

J. Appl. Phys. 85, 803 (1999); http://dx.doi.org/10.1063/1.369163 (4 pages) | Cited 21 times

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Boron diffusion was studied in the BF2+ implanted Si by secondary ion mass spectroscopy. Anomalous boron diffusion was observed in the excess Si region of the amorphized layer at low temperatures below 300 °C. This was explained by a diffusion model where boron was assumed to diffuse by way of an intermediate species BI formed of interstitial Si(SiI) and substitutional boron. It is also found that fluorine plays a significant role in enhancing boron diffusion even at an annealing temperature as low as 300 °C, although the enhanced boron diffusion was reported only to occur at annealing temperatures above 600 °C. Fluorine may hinder SiI from growing into large clusters which need a high temperature annealing to dissociate into freely migrating species. Exponential diffusion profile of fluorine could be explained by a model of SiI–F complex formation. This complex consumes SiI resulting from small Si clusters which could dissociate at low annealing temperatures. This result also supports that boron diffusion at high annealing temperatures may be suppressed by co-implantation of fluorine. © 1999 American Institute of Physics.
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66.30.J- Diffusion of impurities
61.72.uf Ge and Si
81.05.Cy Elemental semiconductors

Sulfur doping of GaAs with (NH4)2Sx solution

Jong-Lam Lee

J. Appl. Phys. 85, 807 (1999); http://dx.doi.org/10.1063/1.369164 (5 pages) | Cited 5 times

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A novel technique for sulfur doping to GaAs was demonstrated. The surface of GaAs was treated with (NH4)2Sx solution, subsequent to annealing using either furnace or rapid thermal processing. Sulfur atoms adsorbed at the surface of GaAs during the (NH4)2Sx treatment diffuse into GaAs during the annealing. The diffusion profiles of sulfur in both types of annealing treatments show a concave shape from the GaAs surface. Diffusion constants of sulfur determined using the Boltzmann–Matano technique increase with the decrease of sulfur concentration via the depth from the surface of GaAs. This suggests that immobile sulfur donor SAs+ forms at the near surface interacts with a Ga divacancy, and results in the production of mobile As interstitials, IAs. The IAs moves fast toward the inside of GaAs and kickout the SAs+ donor, producing a fast diffusing species of interstitial S atoms. The diffusion coefficients of sulfur determined are 2.5×10−14 cm2/s at 840 °C and 5×10−12 cm2/s at 900 °C. The sulfur doping technique is applied to the fabrication of metal-semiconductor field-effect transistors (MESFETs). The MESFETs with 1.0 μm gate length exhibit transconductance of 190 mS/mm, demonstrating the applicability of this technique to the formation of active channel layer of MESFETs. © 1999 American Institute of Physics.
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61.72.uj III-V and II-VI semiconductors
81.05.Ea III-V semiconductors
68.35.Fx Diffusion; interface formation
61.72.Cc Kinetics of defect formation and annealing
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