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1 Jun 1998

Volume 83, Issue 11, pp. 5609-7398

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Quantitative magnetic force microscopy on perpendicularly magnetized samples

Hans J. Hug, B. Stiefel, P. J. A. van Schendel, A. Moser, R. Hofer, S. Martin, H.-J. Güntherodt, Steffen Porthun, Leon Abelmann, J. C. Lodder, Gabriel Bochi, and R. C. O’Handley

J. Appl. Phys. 83, 5609 (1998); http://dx.doi.org/10.1063/1.367412 (12 pages) | Cited 60 times

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We present a transfer-function approach to calculate the force on a magnetic force microscope tip and the stray field due to a perpendicularly magnetized medium having an arbitrary magnetization pattern. Under certain conditions, it is possible to calculate the magnetization pattern from the measured force data. We apply this transfer function theory to quantitatively simulate magnetic force microscopy data acquired on a CoNi/Pt multilayer and on an epitaxially grown Cu/Ni/Cu/Si(001) magnetic thin film. The method described here serves as an excellent basis for (i) the definition of the condition for achieving maximum resolution in a specific experiment, (ii) the differences of force and force z-derivative imaging, (iii) the artificial distinction between domain and domain wall contrast, and finally (iv) the influence of various tip shapes on image content. © 1998 American Institute of Physics.
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07.79.Pk Magnetic force microscopes
68.37.Ef Scanning tunneling microscopy (including chemistry induced with STM)
68.37.Ps Atomic force microscopy (AFM)
68.37.Rt Magnetic force microscopy (MFM)
68.37.Uv Near-field scanning microscopy and spectroscopy

Enhanced magneto-optical Kerr effect in oxidized Co thin films

B. Rellinghaus, S. Fernandez de Avila, D. Weller, G. Armelles, R. Beyers, and A. Kellock

J. Appl. Phys. 83, 5621 (1998); http://dx.doi.org/10.1063/1.367413 (5 pages) | Cited 2 times

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We have studied the structural and magneto-optical properties of postdeposition oxidized Co thin films. The oxidization process leads to the formation of a double-layered structure of fcc Co3O4 on top of metallic Co. The magneto-optical Kerr effect (MOKE), measured in the range 0.8 eV ⩽ EPh ⩽ 5.5 eV reveals characteristic dependencies of the MOKE spectra on annealing temperature and time. In particular, we observe resonance-type enhancements of the Kerr effects by up to a factor of 10 compared with unannealed metallic Co. The experimental data are quantitatively reproduced by bilayer optical stack calculations. © 1998 American Institute of Physics.
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78.66.Nk Insulators
81.65.Mq Oxidation
78.20.Ls Magneto-optical effects
81.05.Bx Metals, semimetals, and alloys
61.72.Cc Kinetics of defect formation and annealing

Relaxation of electron polarization for optically pumped rubidium atoms

W. Nagengast, A. Nass, C. Grosshauser, K. Rith, and F. Schmidt

J. Appl. Phys. 83, 5626 (1998); http://dx.doi.org/10.1063/1.367414 (6 pages) | Cited 3 times

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Relaxation time constants of electron polarization, 〈Sz〉, for optically pumped rubidium atoms in a drifilm coated glass cell have been investigated with the Faraday rotation method. The dependence of the 〈Sz〉 relaxation time on pump cell temperature, rubidium density and applied magnetic field has been determined with high precision. The measurements allow the determination of the local magnetic field on the surface, alkali-wall binding energy and wall-dwell time. Furthermore, the change of relaxation time caused by admixtures of molecular hydrogen, nitrogen and oxygen has been investigated. No influence due to the addition of hydrogen could be detected up to a density of 3.3×1014 cm−3 at typical rubidium densities of several 1011 cm−3. The cross section for depolarizing collisons with molecular oxygen has been determined to be 7.50×10−15 cm2. The corresponding cross section for nitrogen was found to be two orders of magnitude lower. The experimental results are discussed in respect to the performance of spin exchange sources for nuclear polarized hydrogen and deuterium. © 1998 American Institute of Physics.
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32.80.Xx Level crossing and optical pumping
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Electric field singularity at an electrode tip in a nonlinear electrical conductor

Agnes Vojta and David R. Clarke

J. Appl. Phys. 83, 5632 (1998); http://dx.doi.org/10.1063/1.367415 (4 pages) | Cited 3 times

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By analogy with the well-established analysis for the elastic field singularity around a crack tip in a nonlinear elastic material, it is shown that the electric field, E, at the tip of a flat conducting plate in a nonlinear conducting material obeying jαEN has a field singularity of the form r−1/(N+1) where r is the distance from the plate. The corresponding current density scales with distance from the tip as jαr−N/(N+1). Electrical network simulations of a highly conducting electrode in a nonlinear conducting medium support these scaling relationships. © 1998 American Institute of Physics.
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41.20.Cv Electrostatics; Poisson and Laplace equations, boundary-value problems

Particle acceleration by laser fields in a dielectric disk-loaded waveguide

L. C. Steinhauer, R. D. Romea, W. D. Kimura, and J. R. Fontana

J. Appl. Phys. 83, 5636 (1998); http://dx.doi.org/10.1063/1.367416 (8 pages) | Cited 2 times

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A new method is proposed for accelerating relativistic charged particle beams in a vacuum by a laser. The laser propagates in an overmoded waveguide interrupted periodically by thin dielectric disks spaced many wavelengths apart. The particle beam travels along the waveguide axis, passing through irises in the disks. The disks correct for slippage of the particle phase relative to the laser wave. This concept exploits the inverse of familiar radiation processes (transition radiation, diffraction radiation). Several practical accelerator issues are incorporated in a systems analysis. Acceleration gradients in the GeV/m range are projected using lasers with ∼ 100 GW power. This represents more than an order of magnitude stronger coupling of the laser energy compared to other laser acceleration schemes. © 1998 American Institute of Physics.
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29.20.-c Accelerators
42.62.-b Laser applications
85.50.-n Dielectric, ferroelectric, and piezoelectric devices
84.40.Az Waveguides, transmission lines, striplines

Dynamics of electromagnetic field in imploding conducting shell

Yu. Dolinsky and T. Elperin

J. Appl. Phys. 83, 5644 (1998); http://dx.doi.org/10.1063/1.367417 (6 pages) | Cited 1 time

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In this study we derived explicit analytical solutions of two problems. First is a problem of accumulating of magnetic fields in imploding shells with different geometries. The second problem is determining the eigenmodes of a resonator with moving walls. Using the obtained exact solutions we found the regions of validity of an adiabatic approximation when the frequency of the resonator follows the instantaneous values of geometrical parameters, and the amplitude is determined by a conservation of a magnetic flux. The obtained solutions are of interest in design of devices for generation of ultrastrong magnetic fields and powerful electromagnetic radiation. © 1998 American Institute of Physics.
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03.50.De Classical electromagnetism, Maxwell equations

Determination of ordinary refractive index profile for a planar waveguide by transmission spectrum analysis

Shiuh Chao, Yun-Chiao Chen, and Huai-Yi Chen

J. Appl. Phys. 83, 5650 (1998); http://dx.doi.org/10.1063/1.367418 (8 pages) | Cited 3 times

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We introduce a new method to determine the ordinary refractive index profile of a planar waveguide on a crystal plate. The index profile of the planar waveguide can be numerically divided into multilayers; the transmission spectrum of the multilayer waveguide can be calculated and numerically analyzed to fit the measured transmission spectrum. We demonstrated this method on a proton exchanged planar waveguide in z-cut LiTaO3. We found that the ordinary refractive index profile of this waveguide can very well be described by a Fermi–Dirac function. The index profile evolution with proton exchange time and anneal time were obtained together with the diffusion coefficients for the proton exchange and anneal processes. We discovered that, for the proton exchange process in LiTaO3, there exists a surface diffusion phenomenon which has a much smaller diffusion coefficient than that of the bulk diffusion. © 1998 American Institute of Physics.
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42.65.Wi Nonlinear waveguides
42.79.Gn Optical waveguides and couplers
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
77.80.-e Ferroelectricity and antiferroelectricity
77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
68.35.Fx Diffusion; interface formation

Valveless pumping using traversing vapor bubbles in microchannels

Thomas K. Jun and Chang-Jin “CJ” Kim

J. Appl. Phys. 83, 5658 (1998); http://dx.doi.org/10.1063/1.367419 (7 pages) | Cited 65 times

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Pumping of fluids in microchannels using the movement of a single or multiple vapor bubble(s) is proposed, analyzed, and demonstrated. The pumping mechanism requires no micromechanical moving parts for actuation by utilizing asymmetric heating which creates a variation in vapor pressure and surface tension due to the heater-induced temperature gradient along the channel. A heat and mass transfer analysis was performed to understand the pumping mechanism and estimate the pumping capability of the micropumping device. To verify the concept and our analysis, a pumping device with a transparent microchannel with a hydraulic diameter of 3.4 μm was fabricated on a silicon wafer using surface micromachining. Experimental results with the first generation device have shown pumping of isopropanol at velocities as high as 160 μm/s (0.5 nl/min flow rate) with a pressure head of approximately 800 Pa. © 1998 American Institute of Physics.
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07.10.Cm Micromechanical devices and systems
47.55.D- Drops and bubbles
07.07.Tw Servo and control equipment; robots

Study on growth processes of particles in germane radio frequency discharges using laser light scattering and scanning electron microscopic methods

Hiroharu Kawasaki, Junichirou Kida, Kazutaka Sakamoto, Tsuyoshi Fukuzawa, Masaharu Shiratani, and Yukio Watanabe

J. Appl. Phys. 83, 5665 (1998); http://dx.doi.org/10.1063/1.367420 (5 pages) | Cited 15 times

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Growth processes of particles formed in germane (GeH4) rf parallel plate discharges are studied using a laser light scattering and scanning electron microscopic methods. For GeH4(5%)+He, 30 sccm, 80 Pa, and a relatively high power of 40 W(0.51 W/cm2), particles begin to be observed from a very early time of about 0.13 s after the discharge initiation around the plasma/sheath boundary near the powered electrode, where emission intensity of Ge atoms is high. This appearance time of particles is extremely early compared to that (about 0.5 s) in silane (SiH4) rf discharges. The localized existence of particles suggests that short-lifetime radicals being generated at a high rate may contribute to the particle nucleation, while little information about reaction rates for GeHx (x = 0−3) radicals is available. After nucleation and subsequent initial growth of particles, they coagulate quickly with one another, which brings about a growth rate considerably high compared to that for SiH4. Some Ge particles become submicron in size at an early time of 0.3 s and fall to the plasma/sheath boundary near the lower grounded electrode. For such a high coagulation rate (growth rate is about 800 nm/s), particles have irregular nonspherical shapes and most of them are agglomerates composed of chains, while they are almost spherical with a roughness of primary particle size (about 10 nm) for a low coagulation rate (growth rate is about 100 nm/s). Fast appearance of particles for GeH4 discharges also brings about rapid decrease in discharge voltage and absolute value of self-bias voltage. © 1998 American Institute of Physics.
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52.80.Pi High-frequency and RF discharges
52.77.Bn Etching and cleaning
52.77.Dq Plasma-based ion implantation and deposition
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
85.40.Sz Deposition technology
78.35.+c Brillouin and Rayleigh scattering; other light scattering

Plasma transport around dust agglomerates having complex shapes

Eric R. Keiter and Mark J. Kushner

J. Appl. Phys. 83, 5670 (1998); http://dx.doi.org/10.1063/1.367421 (8 pages) | Cited 6 times

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Dust particles generated in low temperature plasmas as used for microelectronics fabrication are often agglomerates of smaller monodisperse particles. The transport of these agglomerates, and the subsequent contamination of surfaces, depends on the details of ion-momentum transfer (ion drag) to, and electrostatic forces on, the agglomerate. Given that the charge distribution on the surface of the agglomerate and local electric fields in the vicinity of the agglomerate depend on its shape, the subsequent forces on the agglomerate will also be a function of shape. In this article, we describe results from a simulation in which plasma transport around, and the charging of, agglomerates are investigated. We find that the charge distribution on the agglomerates is generally nonuniform, a consequence of both shadowing and charge depletion. The ion-momentum transfer cross section, calculated using a Monte Carlo simulation, also depends on the shape of the agglomerate.© 1998 American Institute of Physics.
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52.25.Fi Transport properties
52.25.Vy Impurities in plasmas
52.65.Pp Monte Carlo methods

Streamer mechanism for negative corona current pulses

Mirko Černák, Tatsuzo Hosokawa, Shigeo Kobayashi, and Teruo Kaneda

J. Appl. Phys. 83, 5678 (1998); http://dx.doi.org/10.1063/1.367422 (13 pages) | Cited 20 times

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Current wave forms of initial stages of breakdown and corona formation in a short negative point-to-plane gap have been measured with a nanosecond time resolution in air, O2, and N2 at pressures 13.33–100 kPa, and at various overvoltages. The experiments revealed the existence of a stepped form of negative corona Trichel pulses in O2 at atmospheric pressure. To test existing models for the negative corona pulse formation, effects of changing cathode secondary electron emission were studied using a brass cathode coated by CuI and graphite. It is concluded that a negative corona (Trichel) pulse is associated with the ignition of a cathode-directed streamer in the immediate vicinity of the cathode and the subsequent formation of a glow-discharge-type cathode region at the streamer arrival to the cathode. The implications of these results to negative corona applications are discussed. © 1998 American Institute of Physics.
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52.80.Hc Glow; corona

Multitube surface-wave discharges for increased gas throughput at atmospheric pressure

M. Moisan, Z. Zakrzewski, R. Etemadi, and J. C. Rostaing

J. Appl. Phys. 83, 5691 (1998); http://dx.doi.org/10.1063/1.367423 (11 pages) | Cited 24 times

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Large diameter (>10 mm) microwave discharges at atmospheric pressure are often constricted transversely and, when large gas flow rates are used, unstable as far as microwave power coupling is concerned. A group of small bore tubes can be used instead to provide the same gas throughput and ensure a higher probability of interaction of molecules to be processed with the carrier gas. The solution presented provides equal power sharing in these small diameter plasma columns and it employs preferably a single microwave field applicator, therefore enabling one to use only one power generator and yielding a compact system. This scheme is based on the properties of surface-wave sustained plasmas and it calls on basic principles of waveguide circuitry. © 1998 American Institute of Physics.
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52.80.Pi High-frequency and RF discharges
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Particle-size effect on the ferroelectric phase transition in PbSc1/2Ta1/2O3 ceramics

Yung Park, Kevin M. Knowles, and Kurn Cho

J. Appl. Phys. 83, 5702 (1998); http://dx.doi.org/10.1063/1.367424 (7 pages) | Cited 17 times

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The particle-size dependence on the ferroelectric phase transition in nanocrystalline PbSc1/2Ta1/2O3 ceramics has been investigated for particles in the 0.01–0.16 μm size range. The phase transition was monitored through measurement of the dielectric constant as a function of temperature, variable temperature x-ray diffraction, and differential scanning calorimetry. The c/a tetragonality ratio decreased monotonically with particle size, reducing to unity at 0 °C for particles ⩽ 0.053 μm in size. The ferroelectric transition temperature Tc decreased gradually and the phase transition became more diffuse in nature as the particle size decreased. Below a mean particle size of 0.02 μm there was no peak in either the dielectric constant or the differential scanning calorimetry curve as a function of temperature, even though variable temperature x-ray diffraction could detect tetragonality indicative of ferroelectric distortions at sufficiently low temperatures down to the smallest crystallite size of 0.01 μm. © 1998 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
77.22.Ch Permittivity (dielectric function)
61.46.-w Structure of nanoscale materials

Electron microscopy studies of ion implanted silicon for seeding electroless copper films

G. K. Muralidhar, S. Bhansali, A. Pogany, and D. K. Sood

J. Appl. Phys. 83, 5709 (1998); http://dx.doi.org/10.1063/1.367425 (5 pages) | Cited 6 times

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The feasibility of ion implantation induced electroless copper plating as an effective technique for micro electromechanical systems fabrication was explored by our group recently. This paper aims at investigating such implanted surfaces in order to understand the mechanism assisting the plating. Si was implanted with Pd+ ions at an ion energy of 19 keV in a metal vapour vacuum arc (MEVVA) implanter. The implantation dose ranged between 7×1014 and 2×1017 ions/cm2. The substrates were characterized using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). TEM studies on these substrates indicated that implanted ions tend to form metallic clusters or agglomerates in the substrate. The electroless films nucleate at these clusters. An attempt was made to establish a relationship between implantation dose and cluster size. The topology of the electroless plated films was examined under SEM and the results are discussed in detail. © 1998 American Institute of Physics.
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61.72.uf Ge and Si
73.40.Ns Metal-nonmetal contacts
81.05.Bx Metals, semimetals, and alloys
81.15.Pq Electrodeposition, electroplating
68.37.Hk Scanning electron microscopy (SEM) (including EBIC)
68.37.Lp Transmission electron microscopy (TEM)

Local order of polymer derived amorphous SixCyNz

H. Uhlig, M. Frieß, P. Lamparter, and S. Steeb

J. Appl. Phys. 83, 5714 (1998); http://dx.doi.org/10.1063/1.367426 (5 pages) | Cited 6 times

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We report on the local order of a-Si39C61, a-Si40C24N36, and a-Si26C40N34. The total structure factors and pair correlation functions obtained by x-ray diffraction as well as the coordination numbers of the first coordination sphere are presented. All materials exhibit a distinct short range order. In the case of a-Si39C61, a stoichiometric amorphous SiC phase besides an amorphous carbon phase is formed. Also in the case of a-Si40C24N36 and a-Si26C40N34 phase separation into two amorphous phases is observed. © 1998 American Institute of Physics.
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61.43.Er Other amorphous solids

Thermal stresses in metal-coated optical fibers

Sham-Tsong Shiue and Yi-Shyang Lin

J. Appl. Phys. 83, 5719 (1998); http://dx.doi.org/10.1063/1.367427 (5 pages) | Cited 23 times

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The thermal stresses in metal-coated optical fibers are analyzed. Several thermal stresses are important in a metal-coated optical fiber. First, the interfacial radial stress would produce microbending loss. Secondly, the thermally induced axial force in the glass fiber would induce buckling of the fiber and also results in an increase of bending loss. Thirdly, when the interfacial shear stress is larger than its shear strength, the metal coating would be delaminated from the glass fiber. Finally, when the normal stress in the metal coating is larger than its tensile strength, the metal coating would be broken. These thermal stresses could be minimized by appropriately selecting physical properties of the metal coating and its thickness. To minimize these thermal stresses, the Young’s modulus, thermal expansion coefficient, and Poisson’s ratio of the metal coating should be decreased. On the other hand, the thickness of the metal coating has an optimal value. Based on the strength consideration, an optimal design of the metal-coated optical fiber also is considered. © 1998 American Institute of Physics.
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42.81.-i Fiber optics
62.20.D- Elasticity
62.20.F- Deformation and plasticity
65.40.De Thermal expansion; thermomechanical effects

The role of structural relaxation in the plastic flow of metallic glasses

V. A. Khonik, K. Kitagawa, V. A. Mikhailov, and A. Yu. Vinogradov

J. Appl. Phys. 83, 5724 (1998); http://dx.doi.org/10.1063/1.367428 (8 pages) | Cited 10 times

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The role of structural relaxation in the plastic flow behavior of metallic glasses is analyzed both theoretically and experimentally. The characteristic time of structural relaxation is calculated as a function of glass thermal prehistory. It is revealed that heating above the room temperature by several tens of Kelvins results in a sharp, by several orders of magnitude, decrease of this time. It is argued that localized “inhomogeneous” dislocation-like flow occurs on loading if the characteristic time of structural relaxation is much greater than the characteristic loading time, while “homogeneous” viscous deformation is observed in the opposite case. Precise measurements of acoustic emission in a Co-based metallic glass being loaded at different temperatures and strain rates are employed for verification of this statement. It is shown that the inhomogeneous → homogeneous flow transition occurs at temperatures somewhat higher than T = 400 K, and the transition temperature increases by ≈ 40 K as the strain rate increases by two orders of magnitude. Theoretical estimations show that for the inhomogeneous flow the characteristic time of structural relaxation in the loaded state is indeed much greater than the characteristic loading time. It is concluded that the kinetics of structural relaxation determines the flow mode of metallic glasses in a unique manner. The kinetically “frozen” structural relaxation gives rise to a crystalline-like localized flow under load while intensive structural relaxation facilitates a viscous glass-like behavior. © 1998 American Institute of Physics.
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81.40.Lm Deformation, plasticity, and creep
61.43.Fs Glasses
62.20.F- Deformation and plasticity
81.40.Gh Other heat and thermomechanical treatments
61.72.Hh Indirect evidence of dislocations and other defects (resistivity, slip, creep, strains, internal friction, EPR, NMR, etc.)
61.72.Lk Linear defects: dislocations, disclinations
62.65.+k Acoustical properties of solids

Dynamic stress bridging in granular material

S. G. Bardenhagen and J. U. Brackbill

J. Appl. Phys. 83, 5732 (1998); http://dx.doi.org/10.1063/1.367429 (9 pages) | Cited 23 times

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Through numerical experiments we investigate stress localization in granular material with application to plastic-bonded explosives. The results shed light on static versus dynamic loading, and on the role of an interstitial material between grains. Under static loading, we observe stress localization and bridging in a lattice of polydisperse cylinders in two dimensions. Under dynamic loading, we observe a two wave structure with stress fingers propagating ahead of a normal compaction wave. When an interstitial material is added (a polymeric binder), force fluctuations are substantially reduced under both static and dynamic loading. Under dynamic loading, the structure of the stress wave depends upon the material properties of the binder. As the binder stiffness increases, stress fingering decreases and is replaced by a planar compaction wave. © 1998 American Institute of Physics.
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81.05.Rm Porous materials; granular materials
62.50.-p High-pressure effects in solids and liquids

Experimental characterization of quasi static and shock wave behavior of porous aluminum

Stephane Bonnan, Pierre-Louis Hereil, and Francis Collombet

J. Appl. Phys. 83, 5741 (1998); http://dx.doi.org/10.1063/1.367430 (9 pages) | Cited 10 times

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Experiments of quasi static hydrostatic and uniaxial strain compression, and of shock wave propagation performed on 9% and 17% porous aluminum are presented, analyzed, and compared. Quasi static experiments show the influence of coupling between void collapse and plasticity induced in the matrix on the material macroscopic behavior. The amount of pore compaction appears to be enhanced by the deviatoric stress component present in the uniaxial strain tests and not in the hydrostatic ones. The originality of the plate impact setup and its associated metrology [velocity interferometer system for any reflector (VISAR) interferometry and polyvinylidene fluoride (PVDF) piezoelectric gages] exhibits also the influence of these local physical mechanisms on shock wave propagation in porous aluminum. More, the variations observed between the rise times of shocks seem to point out a preponderance of the dynamic effects (inertia or strain rate) over the material behavior. We observe indeed that the higher the stress in the material, the shorter the shock rise time. This point is confirmed by comparing quasi static and dynamic responses of porous aluminum. Comparison of these experimental results to numerical simulations should be interesting to prove or not this hypothesis. © 1998 American Institute of Physics.
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62.50.-p High-pressure effects in solids and liquids
81.40.Vw Pressure treatment
61.72.Qq Microscopic defects (voids, inclusions, etc.)
62.20.F- Deformation and plasticity
81.40.Lm Deformation, plasticity, and creep

Electromigration failure of integrated circuit metallizations subjected to high-frequency pulsed currents

D. W. Malone and R. E. Hummel

J. Appl. Phys. 83, 5750 (1998); http://dx.doi.org/10.1063/1.367431 (11 pages) | Cited 1 time

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Electromigration life tests were performed on copper-alloyed aluminum test structures that were representative of modern integrated circuit metallization schemes. A total of 18 electrical stress treatments were investigated. One was a steady dc current, and the others were pulsed dc currents varied according to duty cycle and frequency. The duty cycle was varied from 33.3% to 80%, and the frequency was varied such that three distinct orders of magnitude were roughly represented—100 kHz, 1 MHz, and 100 MHz. The median time to failure, t50, was used as the primary basis of comparison between test groups of six–nine samples. There was no discernible dependence of t50 on the pulse frequency. In contrast, the duty cycle, d, played a strong role. Duty cycles greater than 50% produced median lifetimes that varied as 1/d2, while duty cycles equal to and less than 50% produced a shift toward (but not reaching) a 1/d dependence. This shift was most pronounced at the smallest duty cycle of 33.3%, for which lifetimes were midway between the predictions of the 1/d2 and 1/d relationships. Post-test optical micrographs were obtained for each test stripe, and these suggested that the location of electromigration damage was influenced by the pulse duty cycle. Most damage occurred near the cathode contact in all instances, but there was an increased incidence of damage farther downwind with decreasing duty cycle. The results are explained in terms of a Blech length effect that may operate as a result of the bamboo test stripe structure. © 1998 American Institute of Physics.
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85.40.Ls Metallization, contacts, interconnects; device isolation
66.30.Qa Electromigration

Modeling and numerical simulations of microwave-induced ionic transport

S. A. Freeman, J. H. Booske, and R. F. Cooper

J. Appl. Phys. 83, 5761 (1998); http://dx.doi.org/10.1063/1.367432 (12 pages) | Cited 15 times

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A numerical model was developed to simulate and study microwave-induced transport in ionic solids. The model is based on continuum equations, is very general, and could be applied to many materials. The assumptions, boundary conditions, initial conditions, and numerical techniques used in the model are described. Results are presented from a study of microwave driven defect transport in sodium chloride. Static, high-frequency, and quasistatic results show that ponderomotive rectification of vacancy fluxes will act to deplete the vacancies in a near-surface region and will continue to pull vacancies to the surface through diffusion kinetics. The ponderomotive driving force for this transport is characterized over a wide range of variable space. The magnitude of the driving force falls right in the range such that it can explain why microwave-enhanced mass transport is observed in some experimental cases but not in others. © 1998 American Institute of Physics.
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66.30.Dn Theory of diffusion and ionic conduction in solids
66.30.H- Self-diffusion and ionic conduction in nonmetals
61.72.J- Point defects and defect clusters
68.35.Fx Diffusion; interface formation

Tracer-based representation of the mobility in a diffuse antiphase boundary

J. S. Kirkaldy

J. Appl. Phys. 83, 5773 (1998); http://dx.doi.org/10.1063/1.367433 (6 pages) | Cited 2 times

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A tracer representation of the rate coefficient involved in the relaxation of diffuse spherical phase–antiphase boundaries in symmetric B2 binary ordering alloys is presented. Adopting broadly accepted Allen–Cahn [Acta Metall. 27, 1085 (1979)] diffusion-reaction phenomenology, but incorporating vacancy kinetics together with a conventional Landau driving force based upon mean curvature K and the surface free energy σ following Lifshitz, we obtain a non-Arrhenius rate coefficient D = 2Mκ appearing within the Allen–Cahn [Acta Metall. 27, 1085 (1979)] velocity expression which pertains to the symmetric β-brass type coarsening kinetics: v/K = 2Mκ ≃ 2D∗(Tc−T)/(Tc)1/2, where M is a non-Einstein mobility coefficient, κ is the gradient energy coefficient, D∗ is a near-Arrhenius empirical mean tracer diffusion coefficient, and Tc is the critical temperature. This temperature dependency, together with Arrhenius D∗, offers satisfactory agreement with the experiments of Allen, Cahn, and Krzanowski. On the basis of an Allen–Cahn [Acta Metall. 27, 1085 (1979)] σ for a diffuse interface in the mean field approximation this translates to a velocity curvature relation of the form v ∼ D∗σ1/3K. This represents an element of conflict since Allen and Cahn [Acta Metall. 27, 1085 (1979)] have favored a velocity or mobility which is independent of σ. © 1998 American Institute of Physics.
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66.30.Lw Diffusion of other defects
65.20.-w Thermal properties of liquids
65.40.gd Entropy

Effect of wet oxidized AlxGa1−xAs layer on the interdiffusion of InGaAs/GaAs quantum wells

Joong-Seon Choe, Sang-Wan Ryu, Byung-Doo Choe, and H. Lim

J. Appl. Phys. 83, 5779 (1998); http://dx.doi.org/10.1063/1.367505 (4 pages) | Cited 7 times

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The effect of wet oxidized AlAs cap layer and AlGaAs interlayer on the thermal stability of In0.2Ga0.8As/GaAs quantum well (QW) is studied. The QW interdiffusion rate is observed to increase with the Al composition of the AlxGa1−xAs interlayer until x reaches about 0.5 and then saturate for x ≥ 0.5. When the oxidation is performed at 380 °C for 15 min, the threshold value of x for the enhancement of QW interdiffusion is found to be 0.3. It is also confirmed that the QW interdiffusion can only be explained when the strain effect in InGaAs is taken into account. © 1998 American Institute of Physics.
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68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties
68.60.Dv Thermal stability; thermal effects
66.30.Ny Chemical interdiffusion; diffusion barriers
68.35.Fx Diffusion; interface formation
81.65.Mq Oxidation
81.05.Ea III-V semiconductors

Thermal conductivity of κ-Al2O3 and α-Al2O3 wear-resistant coatings

David G. Cahill, S.-M. Lee, and Torbjörn I. Selinder

J. Appl. Phys. 83, 5783 (1998); http://dx.doi.org/10.1063/1.367500 (4 pages) | Cited 23 times

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The thermal conductivities of α-Al2O3 and κ-Al2O3 wear-resistant coatings are measured using the 3ω method in the temperature range 80<T<600 K. The coatings are 13 μm thick and deposited by chemical vapor deposition on substrates of Co-cemented WC. The α-Al2O3 coating has a thermal conductivity comparable to sapphire at T>300 K. The relatively small thermal conductivity of κ-Al2O3, a factor of ∼ 3 smaller than α-Al2O3, suggests that this metastable phase of alumina can be applied as an effective thermal barrier for cutting tools. © 1998 American Institute of Physics.
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66.70.-f Nonelectronic thermal conduction and heat-pulse propagation in solids; thermal waves
68.60.Dv Thermal stability; thermal effects
81.40.Pq Friction, lubrication, and wear
62.20.Qp Friction, tribology, and hardness
81.05.Bx Metals, semimetals, and alloys
81.65.-b Surface treatments

Stress relaxation in Si-doped GaN studied by Raman spectroscopy

In-Hwan Lee, In-Hoon Choi, Cheul-Ro Lee, Eun-joo Shin, Dongho Kim, Sam Kyu Noh, Sung-Jin Son, Ki Yong Lim, and Hyung Jae Lee

J. Appl. Phys. 83, 5787 (1998); http://dx.doi.org/10.1063/1.367501 (5 pages) | Cited 31 times

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We report the Si-doping-induced relaxation of residual stress in GaN epitaxial layers grown on (0001) sapphire substrate by the metalorganic vapor phase epitaxy technique. Micro-Raman spectroscopy is used to assess stress situation in the films with systematically modulated doping concentration from 4.0×1017 up to 1.6×1019 cm−3. As the Si-doping concentration increases, a monotonic decrease of the E2 phonon frequency is observed, which signifies gradual relaxation of the stress in the film. The layers are fully relaxed when electron concentration exceeds 1.6×1019 cm−3. The linear coefficient of shift in Raman frequency (ω) induced by the in-plane biaxial compressive stress (σ∥) is estimated to be Δω/Δσ∥ = 7.7 cm−1/GPa. We suggest that Si doping increases density of misfit dislocation, judging from linewidth of x-ray rocking curve. © 1998 American Institute of Physics.
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68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
78.30.Fs III-V and II-VI semiconductors
78.66.Fd III-V semiconductors
81.15.Kk Vapor phase epitaxy; growth from vapor phase
81.05.Ea III-V semiconductors
71.20.Nr Semiconductor compounds
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