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15 Nov 2009

Volume 106, Issue 10, Articles (10xxxx)

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J. Appl. Phys. 106, 103913 (2009); http://dx.doi.org/10.1063/1.3260240 (5 pages)

P. Krone, D. Makarov, T. Schrefl, and M. Albrecht
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Study of acoustic wave behavior in silicon-based one-dimensional phononic-crystal plates using harmony response analysis

Xuefeng Zhu (祝雪丰), Tao Xu (徐涛), Shengchun Liu (刘盛春), and Jianchun Cheng (程建春)

J. Appl. Phys. 106, 104901 (2009); http://dx.doi.org/10.1063/1.3259401 (6 pages) | Cited 8 times

Online Publication Date: 17 November 2009

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We promote an efficient method named harmony response analysis (HRA) as a comparison with transient response analysis and supercell plane wave expansion (supercell PWE) to study the behavior of Lamb wave in silicon-based one-dimensional composite plates. To implement HRA for dealing with Lamb waves in phononic-crystal plates, the viscous-spring artificial boundaries are employed to eliminate the boundary reflection in maximum. With the calculation of displacement field, the propagations of elastic waves under different frequency loads (inside/outside the completed band gap) are investigated in details. The method is then applied in plates both with and without substrate. We further study the plates with quasiperiodicity (generalized Fibonacci systems and double-period system) and investigate the change in band gaps induced by the quasiperiodicity.
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68.35.Iv Acoustical properties
62.30.+d Mechanical and elastic waves; vibrations
63.20.D- Phonon states and bands, normal modes, and phonon dispersion

Leakage mechanism in flat seals

F. Bottiglione, G. Carbone, L. Mangialardi, and G. Mantriota

J. Appl. Phys. 106, 104902 (2009); http://dx.doi.org/10.1063/1.3254187 (7 pages) | Cited 12 times

Online Publication Date: 17 November 2009

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We present a theoretical approach to estimate the fluid leakage in flat seals. The approach is based on the analogy between the seal-substrate interface and a porous medium. We assume that the interface is constituted of a random distribution of noncontact patches (the pores) and small but numerous contact spots (islands). Leakage may occur only through the pores, of which the lateral size and height are distributed according to a probability density function that we calculate on the basis of a recent theory of contact mechanics. Our theoretical approach is based on a percolation scheme that has never been proposed before and we believe it could be useful to stimulate further theoretical or experimental investigations. Within this percolation scheme we apply critical path analysis to calculate the hydraulic conductivity of the medium and compare our predictions with other calculations very recently presented to the scientific community.
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89.20.Kk Engineering

Schottky’s conjecture on multiplication of field enhancement factors

Ryan Miller, Y. Y. Lau, and John H. Booske

J. Appl. Phys. 106, 104903 (2009); http://dx.doi.org/10.1063/1.3253760 (10 pages) | Cited 2 times

Online Publication Date: 18 November 2009

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Of great interest to high power microwave, millimeter wave to terahertz sources, x-ray tubes, electrons guns, etc., is the electric field enhancement obtained from sharp emitting structures fabricated by various microfabrication methods. In this paper, we use conformal mapping to investigate the field enhancement of several rectilinear geometries, including a single rectangular ridge, a trapezoidal ridge, and their superposition, i.e., one ridge on top of another. We show that the composite field enhancement factor of the double ridge with a microprotrusion on top of a macroprotrusion is dominated by the product of the individual protrusions’ field enhancement factors over a very wide range of geometric aspect ratios, as conjectured by Schottky. Simplified scaling laws are proposed. Significant deviation from Schottky’s product rule occurs almost exclusively when the half-width of the macroprotrusion is less than the height of the microprotrusion. Accurate expressions of the divergent electric field near the sharp edges are derived.
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73.30.+y Surface double layers, Schottky barriers, and work functions

Comparison of amorphous silicon photodiodes and photoconductors for detection of quantum dot biomolecular tags

A. C. Pimentel, D. M. F. Prazeres, V. Chu, and J. P. Conde

J. Appl. Phys. 106, 104904 (2009); http://dx.doi.org/10.1063/1.3259389 (8 pages) | Cited 1 time

Online Publication Date: 20 November 2009

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A comparative study of the performance of hydrogenated amorphous silicon photosensors based on two different device configurations for integration in a microarray platform for biomolecular detection is presented. A perpendicular contact p-i-n photodiode and a parallel contact intrinsic photoconductor, both with an integrated fluorescence filter, are microfabricated for the detection in solution of the fluorescence of the quantum dot Evitag 604 nm, a tag commonly used to label biological molecules. The minimum quantities of quantum dot detected by the p-i-n photodiode and the parallel contact photoconductor were 1 fmol (0.1 nM) and 30 fmol (3 nM), respectively.
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87.80.-y Biophysical techniques (research methods)
85.60.Gz Photodetectors (including infrared and CCD detectors)
87.15.-v Biomolecules: structure and physical properties
85.60.Dw Photodiodes; phototransistors; photoresistors
42.82.Gw Other integrated-optical elements and systems
42.82.Cr Fabrication techniques; lithography, pattern transfer

Quantifying fatigue generated in high strain rate cyclic loading of Norway spruce

Ari Salmi, Lauri Salminen, and Edward Hæggström

J. Appl. Phys. 106, 104905 (2009); http://dx.doi.org/10.1063/1.3257176 (5 pages) | Cited 4 times

Online Publication Date: 20 November 2009

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Papermaking, especially mechanical pulping, consumes much energy. To reduce this energy consumption one has to understand and exploit the phenomena present during the pulping. An important phenomenon to understand is wood fatigue. We quantitatively measure the fatigue generated during high strain rate cyclic loading of spruce wood performed under conditions resembling those present during mechanical pulping. We impacted the samples with 5% strain pulses at 500 Hz. The radial direction stiffness drop in the samples was quantified by 500 kHz ultrasonic through-transmission postimpacting. The depth profile of the generated fatigue was also determined. A dependency of the amount of fatigue generated during cyclic straining on the moisture content was detected. A hypothesis about the temporal and spatial evolution of the fatigue during the process is presented. The results, supporting the hypothesis, provide insight into wood behavior under mechanical pulping conditions.
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89.20.Bb Industrial and technological research and development
89.20.Kk Engineering

Short- and long-range orders in Fe–Cr: A Monte Carlo study

C. Pareige, C. Domain, and P. Olsson

J. Appl. Phys. 106, 104906 (2009); http://dx.doi.org/10.1063/1.3257232 (7 pages) | Cited 5 times

Online Publication Date: 20 November 2009

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Atomistic kinetic Monte Carlo simulations based on the two-band semiempirical cohesive model for Fe–Cr have revealed a body centered tetragonal Fe14Cr ordered compound at very low temperatures. Density functional theory calculations have shown that this structure is more stable than the Fe15Cr compound reported in literature. The study of short-range order, at higher temperatures, has shown that short-range order is not only characterized by the existence of Fe–Cr correlations in the two first neighbor shells but also by the existence of Cr–Cr correlations in the seventh and eighth neighbor shells corresponding to characteristic lengths of the ordered compound. The comparison of these results to neutron diffuse scattering experiments has shown that these characteristic lengths are observed in the experiments. Nevertheless, it appears that a larger spectrum of correlation lengths must exist in the experimental alloy. A Fourier transform of the atomic configuration has shown that the α phase is short-range ordered in the two-phase region.
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65.40.gd Entropy

Thermodynamics of the thermoelectric potential

Christophe Goupil

J. Appl. Phys. 106, 104907 (2009); http://dx.doi.org/10.1063/1.3257250 (4 pages) | Cited 1 time

Online Publication Date: 20 November 2009

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We derive the principal contributions to energy flux and entropy flux in a thermoelectric material using a force-flux description. Using the reduced current u = −J/κ∇T of the coupled thermal and electrical flows, we introduce the so-called thermoelectric potential Tα+1/u. We show that this approach gives a simple description of the thermodynamics of the thermoelectric process, including the heat and entropy production terms. The thermoelectric potential gives a precise estimate of the thermodynamical best working conditions leading to a direct measurement of the irreversible contribution for practical applications where the optimal thermoelectric potential value cannot be maintained.
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72.20.Pa Thermoelectric and thermomagnetic effects
65.40.gd Entropy
72.15.Jf Thermoelectric and thermomagnetic effects

Slow waves on magnetic metamaterials and on chains of plasmonic nanoparticles: Driven solutions in the presence of retardation

O. Zhuromskyy, O. Sydoruk, E. Shamonina, and L. Solymar

J. Appl. Phys. 106, 104908 (2009); http://dx.doi.org/10.1063/1.3259397 (7 pages) | Cited 7 times

Online Publication Date: 23 November 2009

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Slow waves on chains or lattices of resonant elements offer a unique tool for guiding and manipulating the electromagnetic radiation on a subwavelength scale. Applications range from radio waves to optics with two major classes of structures being used: (i) metamaterials made of coupled ring resonators supporting magnetoinductive waves and (ii) plasmonic crystals made of nanoparticles supporting waves of near-field coupling. We derive dispersion equations of both types of slow waves for the case when the interelement coupling is governed by retardation effects, and show how closely they are related. The current distribution is found from Kirchhoff’s equation by inverting the impedance matrix. In contrast to previous treatments power conservation is demonstrated in a form relevant to a finite structure: the input power is shown to be equal to the radiated power plus the powers absorbed in the Ohmic resistance of the elements and the terminal impedance. The relations between frequency and wave number are determined for a 500-element line for two excitations using three different methods. Our approach of retrieval of the dispersion from driven solutions of finite lines is relevant for practical applications and may be used in the design of metamaterials and plasmonic crystals with desired properties.
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81.05.Xj Metamaterials for chiral, bianisotropic and other complex media
41.20.Jb Electromagnetic wave propagation; radiowave propagation
42.70.-a Optical materials

Enhanced mass transport in ultrarapidly heated Ni/Si thin-film multilayers

L. P. Cook, R. E. Cavicchi, N. Bassim, S. Eustis, W. Wong-Ng, I. Levin, U. R. Kattner, C. E. Campbell, C. B. Montgomery, W. F. Egelhoff, and M. D. Vaudin

J. Appl. Phys. 106, 104909 (2009); http://dx.doi.org/10.1063/1.3254225 (6 pages) | Cited 4 times

Online Publication Date: 23 November 2009

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We investigated multilayer and bilayer Ni/Si thin films by nanodifferential scanning calorimetry (nano-DSC) at ultrarapid scan rates, in a temperature-time regime not accessible with conventional apparatus. DSC experiments were completed at slower scan rates as well, where it was possible to conduct parallel rapid thermal annealing experiments for comparison. Postexperimental characterization was accomplished by x-ray diffraction, and by transmission electron microscopy (TEM) and energy-filtered TEM of thin cross sections prepared by focused ion beam milling. We found that rate of heating has a profound effect on the resulting microstructure, as well as on the DSC signal. After heating to 560 °C at 120 °C/s, the general microstructure of the multilayer was preserved, in spite of extensive interdiffusion of Ni and Si. By contrast, after heating to 560 °C at 16 000 °C/s, the multilayer films were completely homogeneous with no evidence of the original multilayer microstructure. For the slower scan rates, we interpret the results as indicating a solid state diffusion-nucleation-growth process. At the higher scan rates, we suggest that the temperature increased so rapidly that a metastable liquid was first formed, resulting in complete intermixing of the multilayer, followed by crystallization to form solid phases. The integrated DSC enthalpies for both multilayer and bilayer films are consistent with this interpretation, which is further supported by thermodynamic predictions of metastable Ni/Si melting and solid state Ni/Si interdiffusion. Our results suggest that use of heating rates >10 000 °C/s may open new avenues for intermetallic micro- and nanofabrication, at temperatures well below those prevailing during explosive silicidation.
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81.40.Gh Other heat and thermomechanical treatments
66.30.Ny Chemical interdiffusion; diffusion barriers
64.60.Q- Nucleation
64.70.dg Crystallization of specific substances
64.70.dj Melting of specific substances
65.40.G- Other thermodynamical quantities

On the role of surface plasmon polaritons in the formation of laser-induced periodic surface structures upon irradiation of silicon by femtosecond-laser pulses

Jörn Bonse, Arkadi Rosenfeld, and Jörg Krüger

J. Appl. Phys. 106, 104910 (2009); http://dx.doi.org/10.1063/1.3261734 (5 pages) | Cited 41 times

Online Publication Date: 23 November 2009

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The formation of nearly wavelength-sized laser-induced periodic surface structures (LIPSSs) on single-crystalline silicon upon irradiation with single or multiple femtosecond-laser pulses (pulse duration τ = 130 fs and central wavelength λ = 800 nm) in air is studied experimentally and theoretically. In our theoretical approach, we model the LIPSS formation by combining the generally accepted first-principles theory of Sipe and co-workers with a Drude model in order to account for transient intrapulse changes in the optical properties of the material due to the excitation of a dense electron-hole plasma. Our results are capable to explain quantitatively the spatial periods of the LIPSSs being somewhat smaller than the laser wavelength, their orientation perpendicular to the laser beam polarization, and their characteristic fluence dependence. Moreover, evidence is presented that surface plasmon polaritons play a dominant role during the initial stage of near-wavelength-sized periodic surface structures in femtosecond-laser irradiated silicon, and it is demonstrated that these LIPSSs can be formed in silicon upon irradiation by single femtosecond-laser pulses.
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81.05.Cy Elemental semiconductors
68.35.bg Semiconductors
72.30.+q High-frequency effects; plasma effects
71.36.+c Polaritons (including photon-phonon and photon-magnon interactions)
78.47.J- Ultrafast spectroscopy (<1 psec)
78.68.+m Optical properties of surfaces
73.20.Mf Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)
71.15.-m Methods of electronic structure calculations
61.80.Ba Ultraviolet, visible, and infrared radiation effects (including laser radiation)
61.82.Fk Semiconductors

Extended model of the photoinitiation mechanisms in photopolymer materials

Shui Liu, Michael R. Gleeson, Dusan Sabol, and John T. Sheridan

J. Appl. Phys. 106, 104911 (2009); http://dx.doi.org/10.1063/1.3262586 (10 pages) | Cited 6 times

Online Publication Date: 23 November 2009

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In order to further improve photopolymer materials for applications such as data storage, a deeper understanding of the photochemical mechanisms which are present during the formation of holographic gratings has become ever more crucial. This is especially true of the photoinitiation processes, since holographic data storage requires multiple sequential short exposures. Previously, models describing the temporal variation in the photosensitizer (dye) concentration as a function of exposure have been presented and applied to two different types of photosensitizer, i.e., Methylene Blue and Erythrosine B, in a polyvinyl alcohol/acrylamide based photopolymer. These models include the effects of photosensitizer recovery and bleaching under certain limiting conditions. In this paper, based on a detailed study of the photochemical reactions, the previous models are further developed to more physically represent these effects. This enables a more accurate description of the time varying dye absorption, recovery, and bleaching, and therefore of the generation of primary radicals in photopolymers containing such dyes.
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42.70.Jk Polymers and organics
42.70.Ln Holographic recording materials; optical storage media
42.79.Vb Optical storage systems, optical disks
42.40.My Applications
42.40.Eq Holographic optical elements; holographic gratings
82.50.-m Photochemistry

In situ measurement of surface potential developed on MgO thin film surface under ion irradiation using ion scattering spectroscopy

T. Nagatomi (永富隆清), T. Kuwayama (桑山剛), K. Yoshino (吉野恭平), Y. Takai (高井義造), Y. Morita (森田幸弘), M. Nishitani (西谷幹彦), and M. Kitagawa (北川雅俊)

J. Appl. Phys. 106, 104912 (2009); http://dx.doi.org/10.1063/1.3259428 (11 pages) | Cited 5 times

Online Publication Date: 24 November 2009

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The application of ion scattering spectroscopy (ISS) to the in situ measurement of the surface potential developed on an insulator surface under positive ion irradiation was investigated. The ISS spectra measured for a MgO film of 600 nm thickness on a Si substrate by the irradiation of 950 eV He+ ions revealed that the surface is positively charged by approximately 180 V. For accurate measurement of the surface potential, a correction to take into account the angular deflection of primary ions induced by the high surface potential is required. The dependence of the surface potential on the sample temperature revealed that no charging is induced above 700 °C, indicating that accumulated charges can be removed by heating to 700 °C. From the measurement of the ion-induced secondary electron yield using a collector electrode located in front of the sample surface, the surface potential and ion-induced secondary electron yield were found to be strongly affected by the experimental setup. Secondary electrons produced by the impact of slow positive secondary ions, the maximum energy of which corresponds to the surface potential, play an important role when the bias voltage applied to the collector electrode is positively high for the present experimental setup. The surface potential developed on the surface of MgO films of 600 and 200 nm thickness was measured in situ, revealing that the amount of accumulated charges and the time required to attain the steady state of charging are slightly dependent on the beam current of primary ions and strongly dependent on the thickness of the MgO film. The present results confirmed that the application of ISS has high potential for investigating charging phenomena and the secondary electron emission from insulator surfaces under positive ion irradiation.
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61.80.Jh Ion radiation effects
61.82.Ms Insulators
79.20.Hx Electron impact: secondary emission
79.20.Rf Atomic, molecular, and ion beam impact and interactions with surfaces
68.49.Sf Ion scattering from surfaces (charge transfer, sputtering, SIMS)

Picogram material dosing of microstructures

Sarah S. Bedair and Gary K. Fedder

J. Appl. Phys. 106, 104913 (2009); http://dx.doi.org/10.1063/1.3248305 (7 pages) | Cited 1 time

Online Publication Date: 24 November 2009

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A solution delivery platform comprised of a suspended microcapillary connected to a microwell enables picogram solute deposition on suspended structures. Precision material placement in the capillary from a 100 pl drop inkjetted into the well is achieved without the destruction of the microstructure and adjacent submicron electrostatic gaps. This method scales to smaller structures without the need for drop miniaturization. The theory behind the solute transfer in the system is developed. Three regions in the drying process are observed and match with the model. The “accumulation” region builds solute concentration in the capillary. The “solidification” region initiates the solidification of solute starting at the free end of the capillary. The “termination” region is characterized by a rapid increase in the solidification due to an increase in the well concentration near the end of the drop lifetime. The accumulation time and solidification rate dependence on concentration compare well with the model.
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81.40.-z Treatment of materials and its effects on microstructure, nanostructure, and properties
81.15.Lm Liquid phase epitaxy; deposition from liquid phases (melts, solutions, and surface layers on liquids)

Breakdown of silicon particle detectors under proton irradiation

S. Väyrynen, J. Räisänen, I. Kassamakov, and E. Tuominen

J. Appl. Phys. 106, 104914 (2009); http://dx.doi.org/10.1063/1.3262611 (4 pages) | Cited 4 times

Online Publication Date: 25 November 2009

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Silicon particle detectors made on Czochralski and float zone silicon materials were irradiated with 7 and 9 MeV protons at a temperature of 220 K. During the irradiations, the detectors were biased up to their operating voltage. Specific values for the fluence and flux of the irradiation were found to cause a sudden breakdown in the detectors. We studied the limits of the fluence and the flux in the breakdown as well as the behavior of the detector response function under high flux irradiations. The breakdown was shown to be an edge effect. Additionally, the buildup of an oxide charge is suggested to lead to an increased localized electric field, which in turn triggers a charge carrier multiplication. Furthermore, we studied the influences of the type of silicon material and the configuration of the detector guard rings.
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29.40.Wk Solid-state detectors
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