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15 Jun 1995

Volume 77, Issue 12, pp. 6087-6738

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Extraction of morphological quantities from a digitized medium

David A. Coker and Salvatore Torquato

J. Appl. Phys. 77, 6087 (1995); http://dx.doi.org/10.1063/1.359134 (13 pages) | Cited 25 times

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We present an analysis of the effect of digitization at a moderate resolution on the determination of various morphological quantities for a model three‐dimensional digitized medium. Specifically, we study systems of digitized overlapping spheres which have many of the features found in man‐made and geologic materials. The goal of this paper is to demonstrate which quantities are most sensitive to the process of digitization and resolution. In addition, the question of whether three‐dimensional data sets are necessary to obtain reliable results concerning material structure is answered in the affirmative. © 1995 American Institute of Physics.
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05.40.-a Fluctuation phenomena, random processes, noise, and Brownian motion
81.30.-t Phase diagrams and microstructures developed by solidification and solid-solid phase transformations

Optical absorption by colloidal precipitates in bismuth‐implanted fused silica: Annealing behavior

Seung Y. Park, Robert A. Weeks, and Raymond A. Zuhr

J. Appl. Phys. 77, 6100 (1995); http://dx.doi.org/10.1063/1.359135 (8 pages) | Cited 9 times

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The near‐surface regions of high‐purity fused silica disks (Corning 7940) were modified by implantation with Bi2+ ions at 160 keV and at room temperature. The glasses implanted with a nominal dose of 6×1016 Bi2+ ions/cm2 at ∼5 μA/cm2 were subsequently annealed in oxidizing and inert atmospheres. The annealing temperature ranged from 500 to 1100 °C. The doses retained before and after the anneals were determined from Rutherford backscattering. A broad optical‐absorption band at ∼5 eV (248 nm) was resolved and attributed to surface plasmon resonance from colloidal bismuth metal particles precipitated after implantation and observed by transmission electron microscopy. After annealing in oxygen for 60 min at temperatures ≥1000 °C the bismuth in the sample decreased by ∼70%. Annealing in an oxidizing atmosphere oxidized the metallic precipitates, and oxidation changed the optical absorption of the samples. For samples annealed in argon, a relatively small decrease in retained dose by ∼12% was observed for temperatures ≥1000 °C. Based on the difference in the effects of annealing in oxygen and in argon, the bismuth atoms in the samples annealed in argon are not oxidized and remain in the particles. The small changes in the distribution of bismuth after annealing in argon are due to diffusion of bismuth atoms from colloidal particles to larger particles, i.e., Ostwald ripening, as well as evaporation from the surface of the fused silica. © 1995 American Institute of Physics.  
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78.30.Hv Other nonmetallic inorganics
78.40.Ha Other nonmetallic inorganics
42.70.Ce Glasses, quartz
61.72.up Other materials

Analysis of light‐induced processes in bacteriorhodopsin and its application for spatial light modulation

K. P. J. Reddy

J. Appl. Phys. 77, 6108 (1995); http://dx.doi.org/10.1063/1.359136 (6 pages) | Cited 7 times

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A simplified energy‐level scheme is proposed for the photochemical cycle of the bacteriorhodopsin molecule. Rate equations are solved for the detailed light‐induced processes based on this model and the intensity‐induced population densities in various states of the molecule at steady state are computed which are used to obtain an analytic expression for the absorption coefficient of the modulation beam. Modulation of the probe laser‐beam transmission by the modulation‐laser‐beam intensity‐induced population changes is analyzed. It is predicted that for a probe beam at 412 nm up to 82% modulation can be achieved using a laser beam intensity of 3.2 W/cm2 at 570 nm. For temperatures ∼77 K, the transmission at 610 nm can be switched from zero to 81% for modulating laser intensity of 11 W/cm2. Construction of a spatial light modulator based on bacteriorhodopsin molecules is proposed and some of its features are discussed. © 1995 American Institute of Physics.
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42.30.Lr Modulation and optical transfer functions
42.70.Gi Light-sensitive materials
42.79.Hp Optical processors, correlators, and modulators

Low‐temperature annealing of ion‐implanted KNbO3 waveguides for second‐harmonic generation

Tomas Pliska, Dieter H. Jundt, Daniel Fluck, Peter Günter, Daniel Rytz, Martin Fleuster, and Christoph Buchal

J. Appl. Phys. 77, 6114 (1995); http://dx.doi.org/10.1063/1.359137 (7 pages) | Cited 12 times

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Results on annealing experiments of He+ ion‐implanted KNbO3 planar and channel waveguides are reported. Annealing at 150 °C for several hours leads to a reduction of the waveguide attenuation constant by more than 5 dB cm−1 at a wavelength of 457 nm without significant change of the profile of the mode confining barrier. A minimum waveguide attenuation constant of 1.3 dB cm−1 in planar and 2.2 dB cm−1 in channel waveguides at 515 nm was achieved. Second‐harmonic generation measurements in the waveguides showed that the conversion efficiency can be improved by more than a factor of 2 by the annealing process. © 1995 American Institute of Physics.
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42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation
42.70.Nq Other nonlinear optical materials; photorefractive and semiconductor materials
42.82.Et Waveguides, couplers, and arrays

Fabrication and characterization of pyrophosphoric acid proton exchanged lithium tantalate waveguides

Gillian M. Davis and Nathan A. Lindop

J. Appl. Phys. 77, 6121 (1995); http://dx.doi.org/10.1063/1.359549 (7 pages) | Cited 4 times

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Planar waveguides in z‐cut LiTaO3 have been fabricated by ion exchange in pyrophosphoric acid. The dependence of the refractive index change and waveguide depth on the ion‐exchange time and temperature, and the anneal time and temperature has been investigated. In addition, waveguide transmission and inversion depths have been measured. The ion exchange temperature and duration were varied between 230 and 293 °C and 15 and 90 min, respectively. The anneal temperature and duration were varied between 300 and 594 °C, and 16 and 840 s, respectively. Under certain conditions the depth of the waveguide was shown to have a simple dependence on the processing conditions. The minimum waveguide coupling and propagation loss was measured to be 0.4 dB. Inversion was observed for anneals of 180 s and temperatures of 525–594 °C. © 1995 American Institute of Physics.
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42.82.Cr Fabrication techniques; lithography, pattern transfer
42.82.Et Waveguides, couplers, and arrays

Population mechanisms of the green Er3+:LiYF4 laser

M. Pollnau, W. Lüthy, and H. P. Weber

J. Appl. Phys. 77, 6128 (1995); http://dx.doi.org/10.1063/1.359138 (7 pages) | Cited 11 times

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In computer simulations the mechanisms that lead to room‐temperature continuous‐wave green upconversion lasing in Er3+:LiYF4 are investigated. The rate‐equation system considers the full erbium level scheme up to 2H9/2, ground‐state depletion, excited‐state absorption on the pump and laser wavelengths, three interionic processes, stimulated emission, and the crystal and resonator data of the experiments. Experimental results performed at the University of Hamburg, Germany, are reproduced in the simulation. The influence of different parameters as pump wavelength, absorption cross sections, interionic parameters, dopant concentration, and temperature is investigated. An avalanche effect which exploits the strong cross relaxation from the upper laser level and the upconversion from 4I13/2 leads to an efficient population of the upper laser level. At higher dopant concentrations the cross relaxation becomes detrimental to stimulated emission due to the depletion of the upper laser level. This concentration dependence can be considered as a general behavior of rare‐earth‐doped avalanche lasers. © 1995 American Institute of Physics.  
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42.55.Rz Doped-insulator lasers and other solid state lasers
42.60.Da Resonators, cavities, amplifiers, arrays, and rings
78.45.+h Stimulated emission

Polarization bistability in strained ridge‐waveguide InGaAsP/InP lasers: Experiment and theory

G. Berger, R. Müller, A. Klehr, and M. Voss

J. Appl. Phys. 77, 6135 (1995); http://dx.doi.org/10.1063/1.359139 (10 pages) | Cited 7 times

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New experimental and theoretical results on TE/TM bistability in 1.3 μm ridge‐waveguide InGaAsP/InP bulk lasers at room temperature are presented. Measured polarization resolved light power–current (P–I) characteristics as well as lateral near‐ and far‐field patterns are compared with results from a theoretical model based on the paraxial wave equations for TE‐ and TM‐polarized modes and the diffusion equation for the carrier distribution. The model was numerically evaluated by use of the beam propagation method. The observed TE/TM bistability is explained by the interplay of three different effects: (i) Tensile stress of about 109 dyn/cm2 promotes the TM gain strongly enough to compete with the TE mode. (ii) Improved TM waveguiding due to an enhancement of the effective refractive index near the beam axis caused by carrier depletion with increasing current leads to the onset of TM lasing and TE/TM switching. (iii) The TE/TM transition is accompanied by an abrupt increase of spatial hole burning in the lateral carrier distribution. Because of this nonlinear effect, a lower current is needed to switch the laser back to TE, giving rise to a hysteresis loop in the P–I characteristics and to TE/TM polarization bistability. © 1995 American Institute of Physics.
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42.55.Px Semiconductor lasers; laser diodes
42.65.Pc Optical bistability, multistability, and switching, including local field effects
42.55.Rz Doped-insulator lasers and other solid state lasers

Angular‐selective optical transmittance of anisotropic inhomogeneous Cr‐based films made by sputtering

D. Le Bellac, G. A. Niklasson, and C. G. Granqvist

J. Appl. Phys. 77, 6145 (1995); http://dx.doi.org/10.1063/1.359140 (7 pages) | Cited 19 times

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Thin Cr‐based films were made by sputtering with oblique incidence of the deposition flux onto a substrate. The films had an inclined columnar microstructure, as verified by atomic force microscopy and scanning electron microscopy. The optical transmittance showed pronounced angular selectivity as well as spectral selectivity. Scaling relations were found for the thickness‐dependent transmittance. The optical data could be reconciled with a model based on the Bruggeman effective medium theory. © 1995 American Institute of Physics.  
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78.66.Bz Metals and metallic alloys
68.55.-a Thin film structure and morphology
81.15.Cd Deposition by sputtering

Surface waves in an anisotropic periodically multilayered medium: Influence of the absorption

Catherine Potel and Jean‐François de Belleval

J. Appl. Phys. 77, 6152 (1995); http://dx.doi.org/10.1063/1.359141 (10 pages) | Cited 4 times

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The influence of absorption upon behavior of the reflection coefficient in water for an anisotropic periodically multilayered medium is studied. From observing a trough of the experimental reflection coefficient of a carbon/epoxy composite immersed in water, the propagation modes of the Floquet waves in an infinite anisotropic periodically multilayered medium in vacuum have been studied. This was explained by a mode that we called the multilayered Rayleigh mode. This mode results from a combination of the Floquet waves which propagate in a periodically multilayered medium. This occurs when all the Floquet waves are inhomogeneous. Analyzing the results obtained in the isotropic case permits the more complicated cases to be explained. By analogy with the isotropic case, the multilayered Rayleigh wave is related to the poles and the zeros of the reflection coefficient. The existence of a critical attenuation becomes evident when the reflection coefficient in water for the multilayered medium reaches zero. © 1995 American Institute of Physics.
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68.43.-h Chemisorption/physisorption: adsorbates on surfaces
43.35.Cg Ultrasonic velocity, dispersion, scattering, diffraction, and attenuation in solids; elastic constants

Free electron laser gain: Approximant forms and inclusion of inhomogeneous broadening contributions

G. Dattoli, P. L. Ottaviani, A. Segreto, and G. Altobelli

J. Appl. Phys. 77, 6162 (1995); http://dx.doi.org/10.1063/1.359142 (7 pages) | Cited 5 times

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The free electron laser gain formulae for low‐, intermediate‐, and high‐gain domains are parametrized by means of a simple expression reproducing linear and exponential regimes. The proposed reformulation provides a useful tool of analysis because of its remarkable simplicity and because it offers the possibility of deriving comparably simple gain formulae that include inhomogeneous broadening effects. © 1995 American Institute of Physics.
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41.60.Cr Free-electron lasers
42.60.Da Resonators, cavities, amplifiers, arrays, and rings

Radio‐frequency plasmas in CF4: Self‐consistent modeling of the plasma physics and chemistry

Nikolaos V. Mantzaris, Andreas Boudouvis, and Evangelos Gogolides

J. Appl. Phys. 77, 6169 (1995); http://dx.doi.org/10.1063/1.359143 (12 pages) | Cited 38 times

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A self‐consistent, one‐dimensional simulator for the physics and chemistry of radio frequency plasmas is developed and applied for CF4. The simulator consists of a fluid model for the discharge, a commercial Boltzmann code for calculations of electron energy distribution function (EEDF), a generalized plasma chemistry code, and an interface among the three models. Chemistry calculations are fed back into the physics model and the procedure is repeated until a self‐consistent solution is obtained. The CF4 discharge shows an electronegative behavior with ten times more negative ions than electrons even at low pressures of 100 mTorr. The EEDF high energy tail lies between the Maxwell and Druyvensteyn distribution. The chemistry model predicts densities of 3.5×1012 cm−3 for CF3, 3×1012 cm−3 for CF2, 2.5×1013 cm−3 for F, and 0.7×1012 cm−3 for CF, in agreement with experimental data from a Japanese group. CF and to a lesser extent CF2, are consumed at the surface, and CF, CF2, and F densities and profiles are sensitive to the sticking coefficient and residence time. CF2 and CF are produced mainly from the parent gas CF4 and not its fragments. Finally, the chemistry results are fed back into the physics model and influence the discharge structure, mainly by changing electron densities and the width of the inner core of the positive‐negative ion plasma. Thus, the importance of self‐consistent plasma calculations is demonstrated and justified. © 1995 American Institute of Physics.
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52.77.Bn Etching and cleaning
52.77.Dq Plasma-based ion implantation and deposition
82.33.Xj Plasma reactions (including flowing afterglow and electric discharges)

O2 rf discharge structure in parallel plates reactor at 13.56 MHz for material processing

Mari Shibata, Nobuhiko Nakano, and Toshiaki Makabe

J. Appl. Phys. 77, 6181 (1995); http://dx.doi.org/10.1063/1.359144 (7 pages) | Cited 32 times

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The spatiotemporal structure of O2 rf discharges between parallel plates at 13.56 MHz is investigated by using the relaxation continuum model. The results for pressure of 0.5 Torr and the sustaining voltage of 75–200 sin ωt V are studied by considering the elementary particles, O+2, O+, O−2, O−, electrons, and O in O2. In these conditions, atomic oxygen, formed by the dissociative electron impact in O2 with density of ∼1014 cm−3, plays important role to the rf structure through the associative detachment process. That is, the expanding characteristics of the sheath width unique to the O2 rf discharge are realized with increasing the sustaining voltage. The validity of the numerical result is demonstrated with the spatiotemporal structure by the measurement by the spatiotemporally resolved optical emission spectroscopy. The flux of each particle to the electrode is also discussed. © 1995 American Institute of Physics.
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52.77.Bn Etching and cleaning
52.77.Dq Plasma-based ion implantation and deposition
52.80.Pi High-frequency and RF discharges

Electron density measurements in a magnetically insulated ion diode

M. Tuszewski, W. J. Waganaar, and M. P. Desjarlais

J. Appl. Phys. 77, 6188 (1995); http://dx.doi.org/10.1063/1.359145 (6 pages) | Cited 3 times

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Electron densities between the electrodes of a flashover anode intense ion beam diode are studied with laser interferometry. Visible and infrared data show no measurable density near the anode and at mid‐gap during ion beam emission. Hence, anode or cathode plasma closures do not cause impedance collapse. However, a two‐phase density build‐up observed near the cathode during beam emission appears associated with impedance collapse and with the termination of the ion beam. Substantial density is measured after the end of the ion beam, consistent with ionization of the neutrals produced by the flashover process. © 1995 American Institute of Physics.
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52.40.Mj Particle beam interactions in plasmas
52.70.Kz Optical (ultraviolet, visible, infrared) measurements

Empirical depth profile simulator for ion implantation in 6Hα‐SiC

S. Ahmed, C. J. Barbero, T. W. Sigmon, and J. W. Erickson

J. Appl. Phys. 77, 6194 (1995); http://dx.doi.org/10.1063/1.359146 (7 pages) | Cited 20 times

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Silicon carbide is a semiconductor material suitable for a variety of specialized devices. Implantation profiles of 30–300 keV B, Al, N, and As in 6Hα‐SiC are reported. The profiles, measured by secondary‐ion‐mass spectrometry, are fit with Pearson‐IV curves which require knowledge of the first four moments of the distribution. The moments of the impurity distributions are extracted from the experimental data and fit to simple functions of the ion energies. Thus, an accurate implantation depth profile simulator, based on experimental data for the common dopants in 6Hα‐SiC, is developed. This method results in a more accurate implant simulator than is obtained using conventional first‐principles calculations, primarily due to channeling considerations. © 1995 American Institute of Physics.
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61.72.uf Ge and Si
82.80.Ms Mass spectrometry (including SIMS, multiphoton ionization and resonance ionization mass spectrometry, MALDI)

Orientation selection in thin platinum films on (001) MgO

P. C. McIntyre, C. J. Maggiore, and M. Nastasi

J. Appl. Phys. 77, 6201 (1995); http://dx.doi.org/10.1063/1.359147 (4 pages) | Cited 24 times

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Orientation selection in platinum films of ∼20 nm thickness deposited onto (001) MgO substrates by e‐beam evaporation was investigated through ion beam channeling and x‐ray diffraction. A mixture of crystallites having (111) and (001) orientation was observed in Pt films deposited over a range of substrate temperatures from 25 to 700 °C, with the (111) orientation dominant at low temperatures. The (111) orientation was present in these evaporated films at significantly higher substrate temperatures than reported for Pt films deposited by sputtering or pulsed laser deposition. Both orientations had strongly preferred in‐plane orientations: [110] Pt//[110] MgO for the (001)‐oriented crystallites and [110]Pt//[110] MgO for the (111). The orientation selection process was rationalized based on the expected relative interfacial energies for these two orientations. © 1995 American Institute of Physics.
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68.55.-a Thin film structure and morphology
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy

Dissociation kinetics of hydrogen‐passivated (100) Si/SiO2 interface defects

J. H. Stathis

J. Appl. Phys. 77, 6205 (1995); http://dx.doi.org/10.1063/1.359148 (3 pages) | Cited 29 times

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The activation energy for thermal dissociation of hydrogen from silicon dangling‐bond defects (Pb centers) has been measured using both (111)‐ and (100)‐oriented samples. The behavior of each of the three Pb varieties [P111b at the (111) interface, P100b0 and P100b1 at the (100) interface] is compared. For P111b, excellent agreement with previous results by Brower [Phys. Rev. B 42, 3444 (1990)] is obtained. The activation energies of the (100)‐interface Pb centers are slightly higher, assuming the same vibrational frequency, and, unlike that of P111b, are affected by a postoxidation anneal. © 1995 American Institute of Physics.
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68.35.Dv Composition, segregation; defects and impurities
61.72.Cc Kinetics of defect formation and annealing
82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces

Characterization of photodeposited selenium planar structures by scanning force microscopy

A. Peled, V. Baranauskas, C. Rodrigues, D. Art‐Weisman, L. Grantman, and A. A. Friesem

J. Appl. Phys. 77, 6208 (1995); http://dx.doi.org/10.1063/1.359149 (6 pages) | Cited 6 times

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This article describes the results of a surface morphology study of photodeposited thin film devices of Selenium by scanning force microscopy (SFM). First, the structures of the photodeposited films were investigated at device level dimensions of the order of visible wavelength. Specifically, ultrathin sinusoidal holographic gratings with spatial periods in the range 480–514 nm were visually identified from SFM nanograph images. Second, grain level structural investigation was performed using image processing techniques such as filtering and one‐ and two‐dimensional Fourier transforms analysis. The variation of the surface grain structure was sampled across the Gaussian profiles of the laser photodeposited patterns. It was found that the random amorphous clustering at the perimeter of the deposited structures becomes progressively grainy towards the center, creating protrusions above the surface with trigonal Selenium (t‐Se) crystalline features. Third, performing image enhancement analysis at high magnification—the nanometer level structure was investigated for amorphous Selenium (a‐Se) and the laser thermally induced structural transformations of the a‐Se films. It was found that the atomic solid‐state structure of a‐Se films, previously deduced only by indirect methods, consists mainly of a random mixture of Sex branched chains containing also a small concentration of imperfect ring structures characteristic of the α‐ and β‐monoclinic phases. The triclinic crystalline phase (t‐Se) was identified in the center of the laser overheated regions of the film Gaussian profile. The results enable us to conclude about the debate in the literature regarding the crystalline and amorphous structure of Selenium thin films. © 1995 American Institute of Physics.
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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
68.35.B- Structure of clean surfaces (and surface reconstruction)
68.55.-a Thin film structure and morphology
42.70.Ln Holographic recording materials; optical storage media

Interfacial structure of nanocrystalline Fe73.5Cu1Nb3Si13.5B9 studied by positron annihilation

T. Liu, Z. T. Zhao, Z. X. Xu, R. Z. Ma, Y. H. Guo, H. M. Cao, and Y. Y. Wang

J. Appl. Phys. 77, 6214 (1995); http://dx.doi.org/10.1063/1.359150 (3 pages) | Cited 3 times

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Nanocrystalline Fe73.5Cu1Nb3Si13.5B9 alloy prepared by the crystallization of amorphous alloy has been studied by using the positron annihilation technique. Positron parameters, i.e., lifetime τ1, τ2, and line shape parameter S are obtained as a function of the annealing temperature. The results show that there exist two types of defects at the interfaces of nanocrystalline Fe73.5Cu1Nb3Si13.5B9 alloy: vacancy‐like and vacancy‐like group microvoids characterized by the lifetime τ1 and τ2. The former is in overwhelming majority. The changes of the structural defects corresponding to different stages, structural relaxation, and crystallization are discussed. © 1995 American Institute of Physics.
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61.66.Dk Alloys
75.50.Bb Fe and its alloys
78.70.Bj Positron annihilation

Dislocation multiplication mechanisms in low‐misfit strained epitaxial layers

R. Beanland

J. Appl. Phys. 77, 6217 (1995); http://dx.doi.org/10.1063/1.359151 (6 pages) | Cited 28 times

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The origin of misfit dislocations in significantly relaxed low‐misfit strained layers is considered. The characteristics of strain relief due to heterogeneous dislocation nucleation at particles, nucleation of dislocations at the free surface of the layer, and multiplication mechanisms are considered and compared with the observed relaxation behavior of constant composition layers of InxGa1−xAs layers on (001) GaAs. It is proposed that dislocation multiplication is consistent with a wide range of experimental results. The observation that 60° and edge dislocations are often seen lying above, but parallel to, the interface in significantly relaxed layers has prompted a study of the possible multiplication mechanisms that they may form. It is shown that one in four reactions between 60° dislocations may lead to a pair of spiral dislocation sources, and that a single spiral source that operates only once may form at the end of edge dislocations. © 1995 American Institute of Physics.
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61.72.Lk Linear defects: dislocations, disclinations
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
61.72.Ff Direct observation of dislocations and other defects (etch pits, decoration, electron microscopy, x-ray topography, etc.)

Structure of stacking faults formed in pairs in a ZnSe epitaxial layer on a GaAs(001) buffer layer

J. Tanimura, O. Wada, T. Ogama, Y. Endoh, and M. Imaizumi

J. Appl. Phys. 77, 6223 (1995); http://dx.doi.org/10.1063/1.359152 (5 pages) | Cited 21 times

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Structure of stacking faults formed in pairs in a ZnSe epitaxial layer grown by gas source molecular beam epitaxy on a GaAs(001) buffer layer was determined with transmission electron microscopy. Extrinsic type stacking faults were formed on (111) and (111) planes with the same polarity, which was determined by convergent‐beam electron diffraction. The two stacking faults meet at a point which is a few atomic layers away from the interface between ZnSe and GaAs. Partial dislocations at the edge of the stacking faults were found to be the Shockley type ones with a Burgers vector of 1/6〈211〉. Probable formation processes of the stacking faults have been discussed. © 1995 American Institute of Physics.
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61.72.Nn Stacking faults and other planar or extended defects
68.37.Hk Scanning electron microscopy (SEM) (including EBIC)
68.37.Lp Transmission electron microscopy (TEM)
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.

Theoretical analysis of surface transverse waves propagating on a piezoelectric substrate under shallow groove or thin metal strip gratings

E. Gavignet, S. Ballandras, and E. Bigler

J. Appl. Phys. 77, 6228 (1995); http://dx.doi.org/10.1063/1.359590 (6 pages) | Cited 5 times

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Theoretical calculations are developed in the present study in order to predict propagation characteristics of surface transverse waves (STW) on piezoelectric substrates. A general model has been implemented for both cases of shallow groove or thin metal strip grating resonators. The analysis gives access to the principal STW characteristics (propagation and attenuation coefficients, velocity, electrical and mechanical amplitudes) and the dispersion curve relating the angular frequency to the propagation coefficient. The results obtained are in good agreement with previous results without piezoelectricity. Improvements on theoretical predictions are emphasized for the case of STW propagating under thin metal strips on AT‐cut quartz. © 1995 American Institute of Physics.
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77.65.Dq Acoustoelectric effects and surface acoustic waves (SAW) in piezoelectrics
62.30.+d Mechanical and elastic waves; vibrations
43.35.Pt Surface waves in solids and liquids

Anisotropic networks with stable dipole orientation obtained by photopolymerization in the ferroelectric state

R. A. M. Hikmet and J. Lub

J. Appl. Phys. 77, 6234 (1995); http://dx.doi.org/10.1063/1.359153 (5 pages) | Cited 14 times

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In this study a ferroelectric liquid crystal (FLC) monoacrylate (S)‐4‐(1‐ethoxycarbonyl‐1‐ethyloxy)phenyl 4′‐(11‐acryloyloxyundecyloxy)biphenyl‐4‐carboxylate was used. Room‐temperature spontaneous polarization of the monoacrylate was measured to be 190 nC/cm2. The monoacrylate was provided with 10% LC diacrylate. After inducing macroscopic molecular and dipolar orientation in the ferroelectric phase, polymerization within the reactive system was induced photochemically. In this way an anisotropic polymer network with a spontaneous polarization was produced. Within this network the crosslinks were formed by the diacrylate molecules. The anisotropic network was transparent and highly birefringent. The system showed high thermal stability and remained anisotropic even after being heated to elevated temperatures. The presence of dipolar orientation within the anisotropic networks was characterized by piezoelectric measurements. The piezoelectric coefficient within these networks was found to be highly dependent on the direction of the applied strain. The highest value was measured in the direction perpendicular to the molecular orientation and was 29 pC/N. © 1995 American Institute of Physics.
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77.80.-e Ferroelectricity and antiferroelectricity
77.84.Nh Liquids, emulsions, and suspensions; liquid crystals
61.30.Gd Orientational order of liquid crystals; electric and magnetic field effects on order

Study of Pt diffusion in thin copper films under two kinetic regimes

A. N. Aleshin, V. K. Egorov, B. S. Bokstein, and P. V. Kurkin

J. Appl. Phys. 77, 6239 (1995); http://dx.doi.org/10.1063/1.359154 (5 pages) | Cited 1 time

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The diffusion of platinum in thin copper films has been studied by Rutherford backscattering spectrometry (RBS) under the kinetic conditions B (within the temperature range of 200–290 °C) and C (room temperature). The RBS spectra were modified to concentration curves for both bulk and grain boundary (GB) diffusion. Under the kinetic regime B the triple products KδDb (Db is the GB diffusion coefficient, δ is the GB width, K is the enrichment ratio) were obtained using Whipple’s model. Under the kinetic regime C the absolute value of the GB diffusion coefficient of Pt in Cu films was obtained. A comparison between the data on GB diffusion for the kinetics B extrapolated to room temperature and the data on GB diffusion for the kinetics C enables one to derive the product Kδ and to separate the contribution of segregation into the GB diffusion of Pt in Cu films. © 1995 American Institute of Physics.
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66.30.J- Diffusion of impurities
68.35.Fx Diffusion; interface formation

Sputtered SiNx film for self‐aligned Si‐Zn diffusion into GaAs and AlGaAs

W. X. Zou, R. Boudreau, H. T. Han, T. Bowen, Song Stone Shi, D. S. L. Mui, and J. L. Merz

J. Appl. Phys. 77, 6244 (1995); http://dx.doi.org/10.1063/1.359155 (3 pages)

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A new technology for self‐aligned Si‐Zn diffusion into GaAs and AlGaAs is described. In this technology, closed‐tube Si diffusion is obtained from a sputtered SiNx film, and Zn diffusion self‐aligned to the Si diffusion window is obtained by reusing the SiNx film as the mask. The key to a successful self‐aligned Si‐Zn diffusion is that the SiNx film is controlled to have a proper refractive index profile. © 1995 American Institute of Physics.
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66.30.J- Diffusion of impurities
85.40.Hp Lithography, masks and pattern transfer

Hydrogen‐surface reactions during the growth of hydrogenated amorphous silicon by reactive magnetron sputtering: A real time kinetic study by in situ infrared absorption

M. Katiyar, Y. H. Yang, and J. R. Abelson

J. Appl. Phys. 77, 6247 (1995); http://dx.doi.org/10.1063/1.359156 (10 pages) | Cited 32 times

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This article experimentally identifies the hydrogen incorporation and release processes which control the final hydrogen content of hydrogenated amorphous silicon films (a‐Si:H). We deposit films using reactive magnetron sputtering of a silicon target in an Ar and H2 atmosphere. Hydrogen incorporation or loss is measured using real time infrared reflectance spectroscopy. An optical cavity substrate increases the sensitivity, allowing us to observe Si–H bonding in layers ≥5 Å thick via the stretching mode absorption (1800–2300 cm−1). We observe a narrow component at ∼2100 cm−1 corresponding to all SiHx bonds on the physical surface; the line width allows us to distinguish this contribution from the broader bulk modes. Various combinations of growth flux (isotope labeling, hydrogen partial pressure between 0.1 and 2.0 mTorr) and substrate material (on SiO2, a‐Si, or a‐Si:D) at substrate temperatures between 120 and 350 °C are used to distinguish various mechanisms. From the deposition of a‐Si:H films on SiO2, we quantify the H surface coverage at the end of the nucleation stage (10 Å of growth) to be 1.2±0.3×1015 cm−2, essentially independent of growth conditions. From the evolution of Si–H bonding during the initial growth (≤25 Å), we infer a reduction of the surface area (smoothening) during nucleation and coalescence. During a‐Si:H growth on unhydrogenated a‐Si, we observe H implantation up to a depth of 40 Å, and derive the total flux of arriving H as a function of hydrogen partial pressure. For the exposure of a‐Si:H to atomic deuterium and of a‐Si:D to atomic H, we observe a loss/gain of surface H due to abstraction or exchange reactions. When a‐Si:D or a‐Si films are deposited on a‐Si:H films, we observe H loss from the bulk of the film due to fast particle bombardment at the growing surface. Based on the experimental evidence, we discuss the dependence of various H incorporation and release processes on the incident H flux, substrate temperature, and deposition rate. © 1995 American Institute of Physics.
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81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
81.15.Cd Deposition by sputtering
78.35.+c Brillouin and Rayleigh scattering; other light scattering
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