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1 Apr 1999

Volume 85, Issue 7, pp. 3395-3936

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Fabrication, modeling, and direct evanescent field measurement of tapered optical fiber sensors

P. N. Moar, S. T. Huntington, J. Katsifolis, L. W. Cahill, A. Roberts, and K. A. Nugent

J. Appl. Phys. 85, 3395 (1999); http://dx.doi.org/10.1063/1.369695 (4 pages) | Cited 8 times

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Tapered optical fibers have been fabricated using a flame elongation technique. The evanescent field distribution surrounding the taper region has been measured directly using a scanning near field optical microscope and results are found to be in good agreement with predictions made using a finite difference beam propagation method. © 1999 American Institute of Physics.
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42.81.Pa Sensors, gyros
07.60.Vg Fiber-optic instruments
07.79.Fc Near-field scanning optical microscopes
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Switching of self-organized patterns in mutually modulating liquid crystal devices for beam control

Yoshiki Iino and Peter Davis

J. Appl. Phys. 85, 3399 (1999); http://dx.doi.org/10.1063/1.369696 (7 pages) | Cited 3 times

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An optical circuit for beam pointing using self-organized roll patterns is proposed and demonstrated. The circuit contains two mutually coupled spatial light modulators (SLMs). It is shown that abrupt beam switching can be realized by changing a bias voltage applied to the liquid crystal layer of one of the SLM. The pattern forming and beam switching mechanism is explained using a theoretical model which includes the effects of diffraction, feedback displacement, and nonlinearity of the SLM. © 1999 American Institute of Physics.
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42.79.Hp Optical processors, correlators, and modulators
42.79.Kr Display devices, liquid-crystal devices
42.65.Jx Beam trapping, self-focusing and defocusing; self-phase modulation

Coherence-based edge diffraction sharpening of x-ray images: A simple model

G. Margaritondo and G. Tromba

J. Appl. Phys. 85, 3406 (1999); http://dx.doi.org/10.1063/1.369697 (3 pages) | Cited 36 times

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Recent, striking examples of x-ray image sharpening are based on Fresnel edge diffraction. A simple model shows that image sharpening can be achieved under less stringent conditions as could be thought. The extreme spatial coherence of third-generation synchrotron sources appears helpful but not strictly necessary, and high time coherence is not an essential requirement. These conclusions, consistent with the results of other authors, strongly enhance the potential impact in medical x-ray applications, materials science and other fields. © 1999 American Institute of Physics.
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61.05.cc Theories of x-ray diffraction and scattering
61.05.cp X-ray diffraction
87.64.Bx Electron, neutron and x-ray diffraction and scattering

Band-engineered semiconductor optical waveguides for integral transform implementation

D. Dragoman and M. Dragoman

J. Appl. Phys. 85, 3409 (1999); http://dx.doi.org/10.1063/1.369771 (4 pages) | Cited 1 time

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The article proposes the implementation of integral transforms using band-engineered semiconductor waveguides. This application could open a new perspective regarding optical computing. © 1999 American Institute of Physics.  
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42.79.Gn Optical waveguides and couplers
42.79.Ry Gradient-index (GRIN) devices
42.79.Ta Optical computers, logic elements, interconnects, switches; neural networks
02.30.-f Function theory, analysis

Ultraviolet-photosensitive effect of sol–gel-derived GeO2–SiO2 glasses

Hikari Shigemura, Yoji Kawamoto, Junji Nishii, and Masahide Takahashi

J. Appl. Phys. 85, 3413 (1999); http://dx.doi.org/10.1063/1.369698 (6 pages) | Cited 15 times

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Germanosilicate glasses are prepared by a sol–gel method and the ultraviolet (UV) photosensitivity of the glasses is investigated by optical absorption, electron spin resonance, and photoluminescence measurements. A KrF pulsed laser and a Hg lamp are used as UV light sources. The concentrations of intrinsic germanium-related oxygen-deficient centers in the glasses are successfully controlled by sintering conditions; in air or under reduced pressure. One-order larger intensity of the 5 eV absorption band is observed in the sol–gel glass sintered under the latter condition, as compared to a fiber preform of almost the same composition, which is formed by the vapor-phase axial deposition method. The effect of irradiation with KrF laser pulses on sol–gel glass is different from that on preform glass. On the other hand, the Hg-lamp illumination has the same effect on both sol–gel glass and preform glass. Based on these results, we discuss the defect states in sol–gel-derived glass and fiber preform glass and also the mechanisms of photochemical reactions under these two UV light sources. © 1999 American Institute of Physics.
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42.70.Ce Glasses, quartz
42.70.Gi Light-sensitive materials
61.80.Ba Ultraviolet, visible, and infrared radiation effects (including laser radiation)
81.05.Kf Glasses (including metallic glasses)
61.82.Ms Insulators
61.43.Fs Glasses
81.10.Dn Growth from solutions
81.10.Fq Growth from melts; zone melting and refining
81.15.Lm Liquid phase epitaxy; deposition from liquid phases (melts, solutions, and surface layers on liquids)
76.30.Mi Color centers and other defects
78.40.Pg Disordered solids
78.55.Hx Other solid inorganic materials

Legendre polynomial approach for modeling free-ultrasonic waves in multilayered plates

J. E. Lefebvre, V. Zhang, J. Gazalet, and T. Gryba

J. Appl. Phys. 85, 3419 (1999); http://dx.doi.org/10.1063/1.369699 (9 pages) | Cited 16 times

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Modeled on the Laguerre polynomial approach used for surface acoustic waves, a formulation is presented for the study of free-acoustic wave propagation in layered plates. It uses the Legendre polynomials. Each layer can be of arbitrary anisotropy and piezoelectricity with arbitrary crystal orientation with the only restriction that the parameters of the constituent materials are close to each other. Formulations are given for open-circuit and short-circuit surfaces. Phase velocity dispersion curves, attenuations, power distributions, and field profiles are easily obtained from an algorithm easily implemented on a computer using commercial software. Numerical results are given for AlAs/GaAs multilayered structures which illustrate the capabilities of the described method. Its major advantages are: (i) in a unified formulation, all types of modes, surface modes, interface modes, and plate modes are naturally encompassed. (ii) Large values of the frequency-thickness product as compared to the values allowed by the usual methods may be dealt with. (iii) For propagation loss calculation, the usual multivariable search is avoided since the proposed method naturally works in the complex plane. © 1999 American Institute of Physics.
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68.35.Gy Mechanical properties; surface strains
02.10.De Algebraic structures and number theory
62.65.+k Acoustical properties of solids
77.65.Dq Acoustoelectric effects and surface acoustic waves (SAW) in piezoelectrics
43.35.Pt Surface waves in solids and liquids

Radio-frequency plasma potential variations originating from capacitive coupling from the coil antenna in inductively coupled plasmas

M. Watanabe, D. M. Shaw, G. J. Collins, and H. Sugai

J. Appl. Phys. 85, 3428 (1999); http://dx.doi.org/10.1063/1.369700 (7 pages) | Cited 15 times

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The radio-frequency plasma potential in a stove top inductively coupled plasma source is measured by a capacitive probe. The experimental results are compared to a crude circuit model which accounts for capacitive coupling between the rf coil and the bulk plasma. The capacitive coupling model has three terms: the dielectric window capacitance, the sheath capacitance between the dielectric window and the bulk plasma, and the bulk plasma to ground sheath capacitance. The crude circuit model predictions are verified by quantitative comparison with the measured rf plasma potential in the bulk argon plasma at pressures from 1 to 20 mTorr and radio-frequency (13.56 MHz) plasma power levels from 60 to 1000 W. Finally, the measured ion energy spectrum, as determined by a retarding potential analyzer, agrees with rf plasma potential measurements over the entire range of experimental conditions. © 1999 American Institute of Physics.
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52.40.Fd Plasma interactions with antennas; plasma-filled waveguides
52.70.Ds Electric and magnetic measurements
52.80.Pi High-frequency and RF discharges
52.40.Hf Plasma-material interactions; boundary layer effects

Plasma sheath model and ion energy distribution for all radio frequencies

Theodoros Panagopoulos and Demetre J. Economou

J. Appl. Phys. 85, 3435 (1999); http://dx.doi.org/10.1063/1.369701 (9 pages) | Cited 68 times

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The spatiotemporal structure of the sheath and the ion energy distribution (IED) at the electrode of a collisionless electropositive glow discharge were studied with a model that is valid for arbitrary radio frequencies (rf). The model is based on the work of P. A. Miller and M. E. Riley [J. Appl. Phys. 82, 3689 (1997)] and uses an effective electric field to which the heavy ions respond. Given the plasma density and electron temperature at the sheath edge, and the waveform of either the potential or total current across the sheath, the spatial and/or temporal profiles of the following quantities were obtained: sheath thickness and capacitance, electron and ion densities, potential, and individual components of the current. An analytic expression for the energy split of the IED function was also obtained. The product ωτi of applied radian frequency ω and ion transit time τi is a critical parameter for describing the sheath dynamics. © 1999 American Institute of Physics.
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52.80.Hc Glow; corona
52.40.Hf Plasma-material interactions; boundary layer effects
52.25.-b Plasma properties

Reduction of laser imprinting using polarization smoothing on a solid-state fusion laser

T. R. Boehly, V. A. Smalyuk, D. D. Meyerhofer, J. P. Knauer, D. K. Bradley, R. S. Craxton, M. J. Guardalben, S. Skupsky, and T. J. Kessler

J. Appl. Phys. 85, 3444 (1999); http://dx.doi.org/10.1063/1.369702 (4 pages) | Cited 23 times

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We demonstrate a laser beam-smoothing technique known as polarization smoothing. A birefringent optical wedge splits the individual laser beams into two orthogonally polarized beams that, when coupled with a distributed phase plate, produce two speckle patterns shifted with respect to one another. This instantaneously reduces the on-target nonuniformity by a factor of √2. We measured this reduction optically and its effect is demonstrated in laser-driven targets. © 1999 American Institute of Physics.
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42.60.Jf Beam characteristics: profile, intensity, and power; spatial pattern formation
42.62.-b Laser applications
52.50.Jm Plasma production and heating by laser beams (laser-foil, laser-cluster, etc.)
42.30.Ms Speckle and moiré patterns
28.52.Cx Fueling, heating and ignition
42.55.Rz Doped-insulator lasers and other solid state lasers
78.20.Fm Birefringence

An analysis of heat transfer and fume production in gas metal arc welding. III

J. Haidar

J. Appl. Phys. 85, 3448 (1999); http://dx.doi.org/10.1063/1.370500 (12 pages) | Cited 24 times

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A two–dimensional dynamic theory for predictions of arc and electrode properties in arc welding has been used to investigate heat transfer phenomena in the welding wire in gas metal arc welding (GMAW). The theory is a unified treatment of the welding wire, the plasma and the workpiece and includes a free surface treatment for the welding drops, accounting for the effects of inertia, gravity, surface tension, arc pressure, magnetic forces, and viscous drag by the gas flow around the drop. Also, the theory accounts for the variation of the surface tension coefficient with temperature and includes thermal and dynamic phenomena within the solid and liquid phases of the wire, together with a detailed treatment for the electrode sheath regions. Calculations are made for arcs in argon with wires of mild steel at currents between 150 and 325 A. Results of calculations for heat fluxes within the wire suggest that evaporation from the surface of the droplet during droplet growth has an important influence on the heat balance of the wire. The calculated evaporation rates from the droplet surface during droplet growth at the tip of the wire are found to be much higher than measured rates of fume formation in GMAW, suggesting an important recondensation process at the surface of the workpiece. © 1999 American Institute of Physics.
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52.77.Bn Etching and cleaning
52.77.Dq Plasma-based ion implantation and deposition
47.27.T- Turbulent transport processes
82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces

Dynamics of a coplanar-electrode plasma display panel cell. I. Basic operation

Shahid Rauf  and Mark J. Kushner 

J. Appl. Phys. 85, 3460 (1999); http://dx.doi.org/10.1063/1.369703 (10 pages) | Cited 134 times

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Plasma display panels (PDPs) are a technology for large-area high-brightness flat panel displays. There is considerable interest in improving PDP efficiency by optimizing the cell design, input voltage characteristics, operating conditions and gas mixture. In this article, we report on a two-dimensional computer model for PDPs which has been used to investigate the operation of a coplanar-electrode PDP cell sustained in He/Ne/Xe gas mixtures. The plasma transport equations are implicitly integrated in time to enable simulation of complex gas mixtures and PDP cell designs. To resolve the details of the electron dynamics, the electron temperature is computed by solving the electron energy equation. A Monte Carlo simulation for secondary electrons and a radiation transport model for visible light emission are also employed. The basic operation of the PDP cell is described in this article. The first pulse was usually found to initiate a discharge between the top electrodes and the bottom address electrode, which was grounded. Only after a positive surface charge was formed on the bottom dielectric did the discharge shift to being between the coplanar electrodes. For our conditions, radiation from Xe2∗ made a larger contribution to exciting the phosphor for visible light emission than radiation from the resonance states of Xe since radiation from Xe2∗ is optically thin. © 1999 American Institute of Physics.
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52.75.-d Plasma devices
52.25.Fi Transport properties
52.25.-b Plasma properties
85.60.Pg Display systems

Dynamics of a coplanar-electrode plasma display panel. II. Cell optimization

Shahid Rauf and Mark J. Kushner

J. Appl. Phys. 85, 3470 (1999); http://dx.doi.org/10.1063/1.369704 (7 pages) | Cited 51 times

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Plasma display panels (PDPs) are a leading technology for large-area flat panel displays. As a result, there is significant interest in improving their efficiency, luminosity, and lifetime. In this article, results from a two-dimensional model are used to investigate the consequences of operating conditions, gas mixture, cell dimensions, and material properties on the visible light generation capacity (luminosity and efficiency) of a coplanar-electrode PDP cell sustained in He/Ne/Xe gas mixtures. Of the species that dominantly lead to the generation of visible light (Xe∗, Xe∗∗, and Xe2∗), Xe2∗ makes the largest contribution for our conditions since its UV radiation is optically thin and Xe2∗ is efficiently generated from the long-lived xenon metastable. Significant improvements could be made in PDP light generation efficiency by choosing operating conditions that favor production of Xe2∗, such as increasing gas pressure to enhance the three-body collision processes that generate Xe2∗. Gas mixtures with more Ne (or less He) were found to produce more visible light at higher efficiency since electron transport in Ne is less collisional than He and Xe2∗ is produced more efficiently in three body collisions with Ne. PDP light emission characteristics are sensitive to the spacing between the dielectrics and there is an optimum spacing where both total visible light output and efficiency are high. It was found that PDP cells do not generate visible light efficiently during the postavalanche discharge phase due to low values of E/N (electric field/total gas density) in the bulk plasma region. Slight improvements can be made in light generation efficiency be choosing conditions for which PDP cell spends less time in the discharge phase in each cycle. © 1999 American Institute of Physics.
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85.60.Pg Display systems
52.75.-d Plasma devices
52.25.Fi Transport properties
52.20.Fs Electron collisions
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Study of microstructural behavior and nonadiabatic small polaron hopping conduction in BaTiO3 doped lead-vanadate glass and glass-ceramics dispersed with ferroelectric nanocrystals

Manisha Sadhukhan, D. K. Modak, and B. K. Chaudhuri

J. Appl. Phys. 85, 3477 (1999); http://dx.doi.org/10.1063/1.369705 (11 pages) | Cited 9 times

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Multicomponent semiconducting oxide glasses like (80 V2O5–20 PbO)+xBaTiO3 (x = 5–30 wt %) dispersed with nanocrystalline BaTiO3 have been prepared by a fast quenching technique. Results of microstructural study and transport properties (between 80 and 450 K) of these glasses and some glass ceramics have been reported in this article. It has been shown from x-ray diffraction, scanning electron microscopic, and other studies that homogeneous glasses are formed with wide concentrations of BaTiO3 (x ⩽ 30 wt %). Transmission electron microscopic study, however, indicates the presence of nanocrystalline phases in the glass matrix. Mott’s variable range (nonadiabatic) hopping conduction mechanism is found to be valid at the low temperature regime (below θD/4, θD being the Debye temperature) while in the high temperature regime (above θD/2), the polaron hopping models of Schnakenberg as well as Emin and co-workers can quantitatively predict the conductivity data for all these special types of multicomponent glass-nanocrystal composites. The model parameters, obtained from best fit of the experimental data with these models, are consistent with the glass compositions. The dielectric constants of these glasses are found to be very high (comparable to that of bulk BaTiO3) and about two orders of magnitude higher than those of BaTiO3 free (80 V2O5–20 PbO) and other transition metal oxide glasses. This novel character is considered to be due to the embedded nanocrystalline BaTiO3 phases. The glass samples annealed at 300 °C for 9 h in air also showed nano and microcrystalline BaTiO3 phase along with traces of PbV2O6, PbTiO3, TiO2, and Pb2V2O7 phases. Broad anomaly (with a maximum around 390 K) is observed from the thermal variation of dielectric constant data of these partially annealed glass-ceramic samples. This anomaly resembles to the anomaly observed around the Curie temperature (∼393 K) in bulk ferroelectric BaTiO3 crystal. © 1999 American Institute of Physics.
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61.43.Dq Amorphous semiconductors, metals, and alloys
72.80.Ng Disordered solids
61.46.-w Structure of nanoscale materials
77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
72.20.Ee Mobility edges; hopping transport
71.38.-k Polarons and electron-phonon interactions
61.43.Fs Glasses
77.22.Ch Permittivity (dielectric function)

Selective field evaporation in field-ion microscopy for ordered alloys

Xi-jin Ge, Nan-xian Chen, Wen-qing Zhang, and Feng-wu Zhu

J. Appl. Phys. 85, 3488 (1999); http://dx.doi.org/10.1063/1.369706 (6 pages) | Cited 15 times

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Semiempirical pair potentials, obtained by applying the Chen-inversion technique to a cohesion equation of Rose et al. [Phys. Rev. B 29, 2963 (1984)], are employed to assess the bonding energies of surface atoms of intermetallic compounds. This provides a new calculational model of selective field evaporation in field-ion microscopy (FIM). Based on this model, a successful interpretation of FIM image contrasts for Fe3Al,PtCo,Pt3Co,Ni4Mo,Ni3Al, and Ni3Fe is given. © 1999 American Institute of Physics.
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79.70.+q Field emission, ionization, evaporation, and desorption
68.37.Vj Field emission and field-ion microscopy
73.30.+y Surface double layers, Schottky barriers, and work functions
61.50.Lt Crystal binding; cohesive energy

Optimized subamorphizing silicon implants to modify diffusion and activation of arsenic, boron, and phosphorus implants for shallow junction creation

S. Aronowitz, H. Puchner, and J. Kimball

J. Appl. Phys. 85, 3494 (1999); http://dx.doi.org/10.1063/1.369707 (5 pages) | Cited 2 times

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Subamorphizing silicon preimplants were combined with relatively high dose drain (1014atoms/cm2) arsenic, boron, and phosphorus implants. The studies included as-implanted distributions. Extensive secondary ion mass spectrometry and spreading resistance profiling (SRP) analyses were carried out. It was found that the SRP analyses could be used to optimize the silicon implant energy. The resulting dopant profiles showed that not only was channeling suppressed and dopant diffusion reduced but activation also could be controlled. Equivalent medium doped drain regions of 150 nm were created using conventional furnace anneals. It was concluded that subamorphizing silicon preimplants could be used to create very shallow junctions in the medium dose drain regions of silicon-based devices. © 1999 American Institute of Physics.
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61.72.uf Ge and Si
85.40.Ry Impurity doping, diffusion and ion implantation technology
66.30.J- Diffusion of impurities
79.20.Rf Atomic, molecular, and ion beam impact and interactions with surfaces

Redshift of the longitudinal optical phonon in neutron irradiated GaP

K. Kuriyama, Y. Miyamoto, and M. Okada

J. Appl. Phys. 85, 3499 (1999); http://dx.doi.org/10.1063/1.369708 (4 pages) | Cited 5 times

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Redshift of the longitudinal optical (LO) phonon relating to the defect structure in neutron-irradiated GaP has been studied using Raman scattering, electron paramagnetic resonance, x-ray diffraction, and Fourier-transform infrared absorption methods. The defect structure is discussed for the two cases of vacancy-interstitials and antisites using a simple model of the LO–transverse optical phonon frequency splitting (Δω). It is suggested that the slight reduction of Δω originates from the vacancy-interstitial clusters rather than the antisite defects, considering the annealing behavior of the antisite defect concentrations, the volume expansion, and infrared absorption in neutron-irradiated samples. The clusters are associated with a volume expansion of about 0.13% observed in the neutron-irradiated samples. © 1999 American Institute of Physics.
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78.30.Fs III-V and II-VI semiconductors
61.80.Hg Neutron radiation effects
61.82.Fk Semiconductors
61.72.J- Point defects and defect clusters
76.30.Mi Color centers and other defects
61.72.Yx Interaction between different crystal defects; gettering effect
63.20.D- Phonon states and bands, normal modes, and phonon dispersion
61.72.Cc Kinetics of defect formation and annealing

Vacancies and interstitial atoms in e−-irradiated germanium

P. Ehrhart and H. Zillgen

J. Appl. Phys. 85, 3503 (1999); http://dx.doi.org/10.1063/1.369709 (9 pages) | Cited 10 times

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High purity Ge wafers have been irradiated at low temperatures with MeV electrons and have subsequently been investigated by x-ray diffraction methods. The intensity of the Huang diffuse scattering shows that a high concentration of defects (>1019 cm−3) can be frozen in at 4 K. A large fraction of the defects is stabilized in the form of close Frenkel pairs which are characterized by the nearly perfect cancellation of the long range displacement fields of the interstitial atom and the vacancy. We discuss the absolute size of these displacements as well as the introduction rate of the defects, which is of the order of ∑ = 3 cm−1. The high defect introduction rates are at variance to the results of electrical and optical investigations and indicate that these methods detect only a few percent of the total defect concentration which is produced and frozen in at 4 K. The consequences for the understanding of the defect production in Ge and for the assumption of an athermal migration of interstitial atoms are discussed in close relation to similar results for Si. In addition, we discuss the differences between the defect patterns observed after 4 K irradiation to those observed after room-temperature irradiations and the thermally activated defect reactions up to the final annealing at 600 K. © 1999 American Institute of Physics.
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61.72.J- Point defects and defect clusters
71.55.Cn Elemental semiconductors
61.80.Fe Electron and positron radiation effects
61.82.Fk Semiconductors
61.72.Cc Kinetics of defect formation and annealing

Phase formation and thermal stability of mechanical alloyed iron–tantalum

M. Mertinat, U. Herr, D. Oelgeschläger, and K. Samwer

J. Appl. Phys. 85, 3512 (1999); http://dx.doi.org/10.1063/1.369710 (7 pages) | Cited 1 time

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Iron-rich iron–tantalum solid solutions were prepared by mechanical alloying of elemental powder mixtures. At low Ta concentrations the alloys form a crystalline solid solution with bcc structure. At higher contents additionally an amorphous phase appears. The phase fractions and their compositions were determined by x-ray diffraction and Mössbauer spectroscopy. The thermal stability of the supersaturated solid solutions was investigated by differential scanning calorimetry measurements. Upon annealing, the solid solutions are found to establish a metastable equilibrium by precipitation of the amorphous phase before transformation to the equilibrium phases sets in. The results are discussed on the basis of the phase stabilities of the participating stable and metastable phases. It is concluded that the phase formation in this system during milling can be described by a smeared-out polymorphous transition to the amorphous phase with increasing solute content rather than by a metastable phase equilibrium. The possibility of grain boundary wetting with the amorphous phase is discussed. © 1999 American Institute of Physics.
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64.70.K- Solid-solid transitions
76.80.+y Mössbauer effect; other γ-ray spectroscopy
81.30.Bx Phase diagrams of metals, alloys, and oxides
81.05.Bx Metals, semimetals, and alloys
81.30.Hd Constant-composition solid-solid phase transformations: polymorphic, massive, and order-disorder
81.20.Ev Powder processing: powder metallurgy, compaction, sintering, mechanical alloying, and granulation
81.70.Pg Thermal analysis, differential thermal analysis (DTA), differential thermogravimetric analysis
64.75.-g Phase equilibria
81.30.Mh Solid-phase precipitation
61.72.Mm Grain and twin boundaries

Elastic moduli, strength, and fracture initiation at sharp notches in etched single crystal silicon microstructures

Wan Suwito, Martin L. Dunn, Shawn J. Cunningham, and David T. Read

J. Appl. Phys. 85, 3519 (1999); http://dx.doi.org/10.1063/1.369711 (16 pages) | Cited 31 times

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We designed and fabricated a series of micromechanical test structures for microtensile testing by anisotropically etching epitaxial silicon. Specimens were fabricated to study Young’s moduli, the uniaxial tensile strength, and the strength of T-structures which are tensile bars with an abrupt reduced cross section that have a 90° corner at the point of reduction. They are a generic mimic of actual transitions that occur in micromechanical structures due to anisotropic etching. The test structures were loaded in uniaxial tension in a piezoactuated microtensile test apparatus. The applied force and crosshead displacement were recorded and displacements in the specimen gage section were directly measured using a speckle interferometry technique. During tensile loading of the T-structures, fracture always initiates at the sharp 90° corners. This results in an interesting apparent strength scaling where the nominal strength of the structures increases as their width decreases. In order to understand the fracture initiation from the sharp 90° corners of the silicon T-structures, we carried out a complete analysis of the elastic fields at the 90° corners by coupling an asymptotic analysis (to compute the asymptotic radial and angular dependence of the elastic fields up to an arbitrary constant for each loading mode, the stress intensity), and full-field finite element calculations (to determine the magnitude of the stress intensities for specific geometries and loadings). Excellent results are obtained by using a single parameter, the critical mode I stress intensity, to correlate fracture initiation from the sharp 90° corners of the T-structures. © 1999 American Institute of Physics.
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68.60.Bs Mechanical and acoustical properties
81.05.Cy Elemental semiconductors
62.20.F- Deformation and plasticity
81.40.Lm Deformation, plasticity, and creep
62.20.D- Elasticity
81.40.Jj Elasticity and anelasticity, stress-strain relations
81.65.Cf Surface cleaning, etching, patterning
02.70.Dh Finite-element and Galerkin methods

Raman analysis of the E1 and A1 quasi-longitudinal optical and quasi-transverse optical modes in wurtzite AlN

Leah Bergman, Mitra Dutta, Cengiz Balkas, Robert F. Davis, James A. Christman, Dimitri Alexson, and Robert J. Nemanich

J. Appl. Phys. 85, 3535 (1999); http://dx.doi.org/10.1063/1.369712 (5 pages) | Cited 33 times

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This article presents a study of the quasi-longitudinal optical and quasi-transverse optical modes in wurtzite AlN which originate from the interaction of phonons belonging to the A1 and E1 symmetry groups. In order to analyze the allowed quasi as well as pure Raman modes, the modes were observed in a rotating crystallographic coordinate system, and the Raman tensors of the wurtzite crystal structure were calculated as a function of the crystallographic rotation. The frequencies of the quasimodes of wurtzite AlN were also analyzed in terms of the interaction of the polar phonons with the long range electrostatic field model. The experimental values of the Raman frequencies of the quasiphonons concur with these expected from the model, implying that the long range electrostatic field dominates the short range forces for polar phonons in AlN. © 1999 American Institute of Physics.
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78.30.Fs III-V and II-VI semiconductors
63.20.-e Phonons in crystal lattices

Thermal wave reflection and refraction: Theoretical and experimental evidence

M. Bertolotti, G. L. Liakhou, R. Li Voti, S. Paoloni, and C. Sibilia

J. Appl. Phys. 85, 3540 (1999); http://dx.doi.org/10.1063/1.369713 (6 pages) | Cited 7 times

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This article describes and proves the basic phenomena which take place when thermal waves approach an interface between two media: the reflection and the refraction. In synthesis the Snell law for plane thermal waves is proved, both theoretically and experimentally, by means of the mirage technique. © 1999 American Institute of Physics.
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44.10.+i Heat conduction
44.35.+c Heat flow in multiphase systems

Simulations of stress evolution and the current density scaling of electromigration-induced failure times in pure and alloyed interconnects

Young-Joon Park, Vaibhav K. Andleigh, and Carl V. Thompson

J. Appl. Phys. 85, 3546 (1999); http://dx.doi.org/10.1063/1.369714 (10 pages) | Cited 55 times

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An electromigration model is developed to simulate the reliability of Al and Al–Cu interconnects. A polynomial expression for the free energy of solution by Murray [Int. Met. Rev. 30, 211 (1985)] was used to calculate the chemical potential for Al and Cu while the diffusivities were defined based on a Cu-trapping model by Rosenberg [J. Vac. Sci. Technol. 9, 263 (1972)]. The effects of Cu on stress evolution and lifetime were investigated in all-bamboo and near-bamboo stud-to-stud structures. In addition, the significance of the effect of mechanical stress on the diffusivity of both Al and Cu was determined in all-bamboo and near-bamboo lines. The void nucleation and growth process was simulated in 200 μm, stud-to-stud lines. Current density scaling behavior for void-nucleation-limited failure and void-growth-limited failure modes was simulated in long, stud-to-stud lines. Current density exponents of both n = 2 for void nucleation and n = 1 for void growth failure modes were found in both pure Al and Al–Cu lines. Limitations of the most widely used current density scaling law (Black’s equation) in the analysis of the reliability of stud-to-stud lines are discussed. By modifying the input materials properties used in this model (when they are known), this model can be adapted to predict the reliability of other interconnect materials such as pure Cu and Cu alloys. © 1999 American Institute of Physics.
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85.40.Ls Metallization, contacts, interconnects; device isolation
66.30.Qa Electromigration

2 MeV electron irradiation of silicon at elevated temperatures: Influence on platinum diffusion and creation of electrically active defects

D. C. Schmidt, B. G. Svensson, J. L. Lindström, S. Godey, E. Ntsoenzok, J. F. Barbot, and C. Blanchard

J. Appl. Phys. 85, 3556 (1999); http://dx.doi.org/10.1063/1.369773 (5 pages) | Cited 2 times

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Platinum has been diffused at 300–800 °C for 30 min into n-type epitaxial silicon samples during 2 MeV electron irradiation using a dose of 1×1017 e− cm−2. Thereafter the samples were characterized by capacitance–voltage measurements and deep level transient spectroscopy. The samples with irradiation temperatures of 500, 600, and 700 °C could be analyzed, while the compensation in the others was too high. Most of the observed deep levels were characterized using the Arrhenius method. Their possible identities are discussed. The deep level of substitutional platinum first appears in the sample irradiated at 600 °C and is the dominant defect level at even higher temperatures. We observe that at a chosen distance from the sample surface (17 μm), the concentration of electrically active platinum after an irradiation at 700 °C is a factor of 1000 higher than in an ordinarily diffused sample. Taking into account experiments where platinum was diffused into pre-irradiated samples, the observed behavior is attributed to a reduced correlated recombination of interstitials and vacancies. © 1999 American Institute of Physics.
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61.80.Fe Electron and positron radiation effects
61.82.Fk Semiconductors
66.30.J- Diffusion of impurities
71.55.Cn Elemental semiconductors
61.72.J- Point defects and defect clusters
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
73.61.Cw Elemental semiconductors

Influence of the domain size on the band gap of ordered (GaIn)P

Torsten Saß, Ines Pietzonka, and Heidemarie Schmidt

J. Appl. Phys. 85, 3561 (1999); http://dx.doi.org/10.1063/1.369715 (4 pages) | Cited 8 times

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The domain size and the band-gap energy of ordered epitaxial (GaIn)P layers have been determined by means of transmission electron microscopy and photoluminescence measurements, respectively. With decreasing domain size the symmetry of the ordered layers is reduced from the trigonal space group R3m (CuPtB type) to the monoclinic Pm space group. Pseudopotential band-structure calculations reveal an increase of the band-gap energy of ordered (GaIn)P with diminishing domain size. This would affect the determination of the degree of order by methods, which rely on the band-gap energy of perfectly ordered (GaIn)P. By correlating the theoretical with the experimental band-gap energies we demonstrate that the order parameter η of layers with small domains is higher if the dependence of the band-gap energy on the domain size is considered. Hence, for the determination of the degree of order not only the band-gap energy, but also the domain size have to be taken into account. © 1999 American Institute of Physics.
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71.20.Nr Semiconductor compounds
73.61.Ey III-V semiconductors
78.55.Cr III-V semiconductors
78.66.Fd III-V semiconductors
68.55.-a Thin film structure and morphology

Growth and characterization of nanoscale 3C–SiC islands on Si substrates

Tatsuro Miyasato, Yong Sun, and J. Keith Wigmore

J. Appl. Phys. 85, 3565 (1999); http://dx.doi.org/10.1063/1.369772 (4 pages) | Cited 5 times

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Three-dimensional nanoscale SiC islands were grown directly on to (111) crystalline Si substrates by reaction with hydrogen-plasma-containing Si and C radicals at temperatures between 650 and 900 °C. X-ray diffraction and transmission electron microscopy observations show that the islands are composed of (111)-oriented cubic SiC (3C–SiC) grains. Nucleation of the islands took place at conical projections on the Si substrate surface produced by hydrogen plasma etching. At the highest substrate temperatures the diameter and density of the islands were smallest, while their height was greatest and their structure most disordered. © 1999 American Institute of Physics.
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81.07.-b Nanoscale materials and structures: fabrication and characterization
61.46.-w Structure of nanoscale materials
81.65.Cf Surface cleaning, etching, patterning
52.77.Bn Etching and cleaning
52.77.Dq Plasma-based ion implantation and deposition
81.15.Kk Vapor phase epitaxy; growth from vapor phase
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