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15 Mar 1997

Volume 81, Issue 6, pp. 2465-2919

Page 2 of 4 Pages Previous Page Next Page | Jump to Page

Vibrational energies of adsorbates on GaAs surfaces

William Pollard

J. Appl. Phys. 81, 2621 (1997); http://dx.doi.org/10.1063/1.363926 (5 pages)

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The structure and properties of adsorbates on GaAs surfaces are investigated. The vibrational states of adsorbed hydrogen and oxygen on GaAs surfaces are calculated. Specific attention is focused on the vibrational energies of surface species and their reported variation with surface stoichiometry. The symmetry and localization of the vibrational states are also discussed. Comparisons are made with experimental high resolution electron energy loss spectroscopy spectra. Our results here agree well with a variety of experimental data. © 1997 American Institute of Physics.
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68.43.Pq Adsorbate vibrations
68.35.Ja Surface and interface dynamics and vibrations
68.35.B- Structure of clean surfaces (and surface reconstruction)
63.20.Pw Localized modes

Nitrogen modification of hydrogenated amorphous carbon films

S. R. P. Silva, J. Robertson, G. A. J. Amaratunga, B. Rafferty, L. M. Brown, J. Schwan, D. F. Franceschini, and G. Mariotto

J. Appl. Phys. 81, 2626 (1997); http://dx.doi.org/10.1063/1.363927 (9 pages) | Cited 190 times

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The effect of nitrogen addition on the structural and electronic properties of hydrogenated amorphous carbon (a-C:H) films has been characterized in terms of its composition, sp3 bonding fraction, infrared and Raman spectra, optical band gap, conductivity, and paramagnetic defect. The variation of conductivity with nitrogen content suggests that N acts as a weak donor, with the conductivity first decreasing and then increasing as the Fermi level moves up in the band gap. Compensated behavior is found at about 7 at. % N, for the deposition conditions used here, where a number of properties show extreme behavior. The paramagnetic defect density and the Urbach tailwidth are each found to decrease with increasing N content. It is unusual to find alloy additions decreasing disorder in this manner. © 1997 American Institute of Physics.
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68.55.-a Thin film structure and morphology
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
78.66.Nk Insulators
78.35.+c Brillouin and Rayleigh scattering; other light scattering
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
71.23.Cq Amorphous semiconductors, metallic glasses, glasses
73.61.Ng Insulators

A C 1s core level x-ray photoelectron diffraction characterization of substitutional carbon in epitaxial Si1−yCy alloys grown on Si(111) and Si(001)

L. Simon, D. Aubel, L. Kubler, J. L. Bischoff, G. Gewinner, and J. L. Balladore

J. Appl. Phys. 81, 2635 (1997); http://dx.doi.org/10.1063/1.363968 (8 pages) | Cited 8 times

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Epitaxial strained growth of Si1−yCy alloys with rather high C concentrations (y ∼ 1.5%) has been performed on Si(111) and Si(001) using molecular beam epitaxy (MBE) Si evaporation and thermal interaction of the growth surface with a low C2H4 pressure at 500 °C. Carbon contents, determined by secondary ion mass spectrometry, infrared (ir) spectrometry, in situ C 1s and Si 2p x-ray photoelectron spectroscopy measurements and x-ray diffraction (XRD), are being compared. Monocrystalline quality of the epilayers is checked by low energy electron diffraction and x-ray photoelectron diffraction (XPD). As indirectly ascertained by the ir local vibration mode (LVM) and a shifted partially strain induced epilayer diffraction line in the θ-2θ XRD analysis, carbon is accommodated in substitutional sites (Csub) whose local atomic order is investigated for the first time by XPD, C 1s polar angle distributions being measured in different azimuthal directions. As the data reveal, for a C emitter, next nearest neighbor bond orientations identical to those for Si atoms in a Si matrix, XPD readily provides direct evidence in favor of Csub positions. Up to now, our limited angular resolution does not allow observation of possible bond orientation changes due to local strain-induced lattice distortions around C atoms. Nevertheless, by increasing growth temperature (600–650 °C) and promoting formation of more C-rich phases (SinC or SiC), the effects of substitution of second or higher nearest Si neighbors by C atoms can be clearly evidenced. By the way, a significant C 1s binding energy difference between Csub and C in C-rich phases is observed and may be used as a signature of the C dilution in the grown epilayer: a characteristic value of 283.8 eV is obtained for the Csub site giving rise to the LVM. © 1997 American Institute of Physics.
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68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
81.05.Hd Other semiconductors
79.60.Bm Clean metal, semiconductor, and insulator surfaces
68.60.Bs Mechanical and acoustical properties
63.20.Pw Localized modes
78.30.Hv Other nonmetallic inorganics
78.66.Li Other semiconductors
62.20.F- Deformation and plasticity

An electrical resistivity study of Ce2Fe16.8 and the Ce2Fe17−xAlx and Ce2Fe17−xSix solid solutions

D. Vandormael, F. Grandjean, H. Bougrine, M. Ausloos, D. P. Middleton, K. H. J. Buschow, and Gary J. Long

J. Appl. Phys. 81, 2643 (1997); http://dx.doi.org/10.1063/1.363928 (3 pages) | Cited 5 times

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Electrical resistivity measurements have been carried out between 20 and 300 K on Ce2Fe16.8, on the Ce2Fe17−xAlx solid solutions, with x = 0.4, 1, 2, 5, 6, 8, and 9, and on the Ce2Fe17−xSix solid solutions, with x = 0.2, 0.4, 1, and 2, with the four probe method. The temperature dependence of the resistivity of Ce2Fe16.8 shows an inflection at 110 K, a feature which is also observed in the temperature dependence of the magnetization and is related to a magnetic phase transition from a helical structure, above 110 K, to a fan structure, below 110 K. The temperature dependence of the resistivity of Ce2Fe16.8 is characteristic over the investigated temperature range of weak antiferromagnetic behavior with incommensurate periodicity as has been observed in the earlier neutron diffraction study. The resistivity of Ce2Fe17−xAlx increases with temperature in agreement with a density of states at the Fermi level dominated by the d band. For a given temperature, the resistivity increases substantially and regularly with x for both series of solid solutions because of an increase in the number of conduction electron scattering potentials. This increase in resistivity also corresponds to a decrease in the number of conduction electrons due to their increasing transfer into the localized cerium 4f orbitals as the cerium valence state changes from a mixture of trivalent and tetravalent in Ce2Fe17 to predominantly trivalent in Ce2Fe17−xAlx and Ce2Fe17−xSix with increasing x. © 1997 American Institute of Physics.
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72.15.Gd Galvanomagnetic and other magnetotransport effects
72.15.Jf Thermoelectric and thermomagnetic effects
75.50.Ww Permanent magnets
71.28.+d Narrow-band systems; intermediate-valence solids
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.30.Kz Magnetic phase boundaries (including classical and quantum magnetic transitions, metamagnetism, etc.)
75.30.Mb Valence fluctuation, Kondo lattice, and heavy-fermion phenomena
75.30.Sg Magnetocaloric effect, magnetic cooling
75.50.Bb Fe and its alloys
75.50.Ee Antiferromagnetics

ac conduction in conducting poly pyrrole-poly vinyl methyl ether polymer composite materials

S. K. Saha, T. K. Mandal, B. M. Mandal, and D. Chakravorty

J. Appl. Phys. 81, 2646 (1997); http://dx.doi.org/10.1063/1.363929 (5 pages) | Cited 9 times

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Composite materials containing conducting polypyrrole and insulating poly (vinyl methyl ether) (PVME) have been synthesized by oxidative polymerization of pyrrole in ethanol using FeCl3 oxidant in the presence of PVME. The ac conductivity measurements have been carried out in the frequency range of 100 Hz to 10 MHz and in the temperature range of 110 to 350 K. The frequency dependent conductivity has been explained on the basis of a small polaron tunnelling mechanism. © 1997 American Institute of Physics.
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72.20.Fr Low-field transport and mobility; piezoresistance
72.80.Le Polymers; organic compounds (including organic semiconductors)
71.38.-k Polarons and electron-phonon interactions

Noise correlation measurements in bipolar transistors. I. Theoretical expressions and extracted current spectral densities

S. Jarrix, C. Delseny, F. Pascal, and G. Lecoy

J. Appl. Phys. 81, 2651 (1997); http://dx.doi.org/10.1063/1.363930 (7 pages) | Cited 17 times

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Low-frequency noise measurements are performed on classical Si bipolar transistors and on AlGaAs/GaAs heterojunction bipolar transistors (HBTs) mounted in a common-emitter configuration. Expressions for the spectral densities are derived taking into account a correlation between base and collector noise sources ib and ic. Values of emitter series resistances and of the base ideality factor are determined from these noise measurements. Then the spectral densities related to ib and ic as well as the cross-spectrum are extracted. In the case of classical Si transistors, the excess noise is attributed to the current noise source ib. The effect of the base series resistance is shown on the white noise. For the HBTs, the white noise is not reached. The excess noise is attributed to the correlated current noise sources ib and ic. From the analysis of the current spectral densities with base current the increase of correlation with bias is revealed. The extracted current spectral densities provide the foundation for the calculation of the coherence function associated to base and collector currents. This coherence function is presented in part II. The shape of the curves shows correlation phenomena to be mainly related to generation-recombination components. Also in part II, the spectral densities associated with the correlated and uncorrelated part of the collector current are extracted and studied versus bias and geometry. © 1997 American Institute of Physics.
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85.30.Pq Bipolar transistors

Noise correlation measurements in bipolar transistors. II. Correlation between base and collector currents

C. Delseny, F. Pascal, S. Jarrix, and G. Lecoy

J. Appl. Phys. 81, 2658 (1997); http://dx.doi.org/10.1063/1.363931 (7 pages) | Cited 4 times

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Low-frequency noise measurements were performed on heterojunction bipolar transistors (HBTs) and presented in part I of this article. These measurements revealed a partial correlation between base and collector noise current sources. With the help of the current spectral densities determined in part I, the coherence function is calculated and studied versus bias in this second part. Important values of the coherence function are obtained at the highest bias. Then the spectral densities Sc and Snc associated to the correlated and uncorrelated parts of the collector current noise source are extracted and analysed. All spectra exhibit excess noise. A difference in shape is clearly observed because of an important generation-recombination component occurring around 1 kHz on the correlated part only. To compare the behavior of different transistors a normalized coupling coefficient is introduced. The correlation is seen to increase with the scaling-down of devices. The investigation of the coupling coefficient with collector current density leads to hypothesis concerning the origin of the generation-recombination (g-r) components. Some components are shown to originate in the intrinsic transistor, and others in the extrinsic one, depending on frequency and type of HBT. Mainly the noise correlation is due to leakage currents and/or recombinations in the base-collector junction. © 1997 American Institute of Physics.
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85.30.Pq Bipolar transistors

Optimum sensitivity and two-dimensional modeling of microwave detected photoconductance decay carrier lifetime measurement

Moustafa Y. Ghannam, Samir F. Mahmoud, and Johan F. Nijs

J. Appl. Phys. 81, 2665 (1997); http://dx.doi.org/10.1063/1.363932 (9 pages) | Cited 3 times

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Optimization of the measurement sensitivity using closed form analytical expressions derived from an electrical equivalent circuit is carried out for microwave detected photoconductance decay system used for nondestructive carrier lifetime measurement in silicon wafers. The effect of transverse inhomogeneity in the sample conductivity on the microwave power reflection is discussed using the equivalent circuit model. The effect of lateral inhomogeneity in the sample conductivity due to local illumination by a source with a laterally varying intensity is studied using an elaborate analytical two-dimensional model. Finally, the effect of transient lateral carrier diffusion in a sample subjected to a pulsed illumination on the extracted value of the lifetime is investigated. © 1997 American Institute of Physics.
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72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping
72.80.Cw Elemental semiconductors
72.40.+w Photoconduction and photovoltaic effects

Relation for the nonequilibrium population of the interface states: Effects on the bias dependence of the ideality factor

G. Gomila and J. M. Rubí

J. Appl. Phys. 81, 2674 (1997); http://dx.doi.org/10.1063/1.364305 (8 pages) | Cited 19 times

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By an analysis of the exchange of carriers through a semiconductor junction, a general relationship for the nonequilibrium population of the interface states in Schottky barrier diodes has been derived. Based on this relationship, an analytical expression for the ideality factor valid in the whole range of applied bias has been given. This quantity exhibits two different behaviours depending on the value of the applied bias with respect to a critical voltage. This voltage, which depends on the properties of the interfacial layer, constitutes a new parameter to complete the characterization of these junctions. A simple interpretation of the different behaviours of the ideality factor has been given in terms of the nonequilibrium charging properties of interface states, which in turn explains why apparently different approaches have given rise to similar results. Finally, the relevance of our results has been considered on the determination of the density of interface states from nonideal current-voltage characteristics and in the evaluation of the effects of the interfacial layer thickness in metal-insulator-semiconductor tunnelling diodes. © 1997 American Institute of Physics.  
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73.40.Ns Metal-nonmetal contacts
73.20.At Surface states, band structure, electron density of states
73.30.+y Surface double layers, Schottky barriers, and work functions

Surface conduction on insulators: Analysis and interpretation of the Faraday cage experiment

H. J. Wintle

J. Appl. Phys. 81, 2682 (1997); http://dx.doi.org/10.1063/1.363971 (4 pages) | Cited 10 times

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We provide a quantitative analysis of the Faraday cage method for determining the leakage of electric charge across the surface of insulators, and correct some inconsistencies in earlier work. We show that it is possible to distinguish between the mechanisms of surface conduction and surface charge driven flow, since in the latter case the time constant depends on the amount of the initial charge and the logarithmic decay rate slows down at long times. © 1997 American Institute of Physics.
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73.25.+i Surface conductivity and carrier phenomena

Continuing degradation of the SiO2/Si interface after hot hole stress

I. S. Al-kofahi, J. F. Zhang, and G. Groeseneken

J. Appl. Phys. 81, 2686 (1997); http://dx.doi.org/10.1063/1.363969 (7 pages) | Cited 14 times

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This article reports new experimental results on the continuing interface trap generation post-hot hole injection and investigates the generation mechanism. The generation post-hole injection is found to be two orders of magnitude slower than that post-irradiation and cannot be satisfactorily explained by the transportation of hydrogen species across the gate oxide. The role played by the recombination of trapped holes with free electrons is examined. There is a lack of correlation between the trapped hole removal and the interface trap creation, which is against the prediction of the trapped hole conversion model. The results indicate that the interface traps generated during and post-stress originate from two different defects. The defect responsible for post-stress generation is excited by hole injection and then converted into an interface trap if a positive gate bias is applied. It is found that generation in a poly-Si gated metal–oxide–semiconductor field effect transistor behaves differently from that in an Al-gated device. The possible causes for this difference are discussed. © 1997 American Institute of Physics.
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73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping
72.20.Ht High-field and nonlinear effects
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
85.30.Tv Field effect devices

Resonant absorption due to electron–electron interaction in coupled quantum dots under an electromagnetic field

Ryuichi Ugajin

J. Appl. Phys. 81, 2693 (1997); http://dx.doi.org/10.1063/1.363933 (6 pages) | Cited 7 times

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In a pair of coupled quantum dots under an external electro-magnetic field, new types of resonant absorption are caused by electron–electron interaction. Quasi-resonance between states of multiple electrons caused by electron–electron interaction can be controlled by an external electric field in the direction of coupling of quantum dots. This kind of resonance produces two types of resonant absorption of a photon, so that far-infrared absorption spectra have additional peaks. These quasi-resonant states of multiple electrons are investigated by optical transitions modulated by an external magnetic field. © 1997 American Institute of Physics.
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78.66.Fd III-V semiconductors
78.20.Jq Electro-optical effects
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
78.30.Fs III-V and II-VI semiconductors
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
73.40.Kp III-V semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions

Gate controlled Coulomb blockade effects in the conduction of a silicon quantum wire

R. A. Smith and H. Ahmed

J. Appl. Phys. 81, 2699 (1997); http://dx.doi.org/10.1063/1.363934 (5 pages) | Cited 75 times

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Side gated silicon quantum wires of nominally uniform 60 nm/70 nm width, 40 nm height, and 4 μm/6 μm length have been fabricated in the silicon-on-insulator configuration. Measurements of the current–voltage characteristics at a temperature of 2.0 K show significant nonlinearities including a zero conductivity blockade region and conductance peaks suggestive of single electron behavior. The blockade size is significantly affected by application of a gate potential and oscillations of the blockade and wire conductivity with gate potential are also observed. These features are explained by a single electron tunneling model of a multiple island system. © 1997 American Institute of Physics.
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73.23.Hk Coulomb blockade; single-electron tunneling
73.40.Lq Other semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
73.61.Cw Elemental semiconductors

Effect of an electric field on the scattering of excitons by free carriers in semiconducting quantum-well structures

Tong San Koh, Yuan-ping Feng, and Harold N. Spector

J. Appl. Phys. 81, 2704 (1997); http://dx.doi.org/10.1063/1.363972 (5 pages) | Cited 3 times

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We have calculated the effect of an electric field applied along the direction of carrier confinement on the scattering of excitons by free carriers in semiconducting quantum-well structures. We find that although the application of the electric field does not change the functional form of the dependence of the differential cross section on the scattering angle or the dependence of the total cross section on the incident wave vector of the free carrier, it does change the magnitude of the total cross section. For scattering of heavy hole excitons by electrons, the peak value of the total elastic cross section decreases with increasing electric field while when the exciton is scattered by heavy holes, the peak value of this cross section increases with electric field. This reduction or enhancement is negligible for narrow wells or for weak fields but there is an appreciable change in the total elastic scattering cross section for wider wells and stronger fields. We also find that the electric field also enhances the ionization cross section for the scattering of excitons by both electrons and heavy holes. © 1997 American Institute of Physics.
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73.61.-r Electrical properties of specific thin films
71.35.-y Excitons and related phenomena

Structural and electrical properties of sputtered vanadium oxide thin films for applications as gas sensing material

D. Manno, A. Serra, M. Di Giulio, G. Micocci, A. Taurino, A. Tepore, and D. Berti

J. Appl. Phys. 81, 2709 (1997); http://dx.doi.org/10.1063/1.363973 (6 pages) | Cited 25 times

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A detailed structural and morphological investigation has been carried out by conventional transmission electron microscopy, high resolution electron microscopy and nanodiffraction methods on vanadium oxide films obtained by reactive rf sputter at a high power discharge (1000 W) and different O2/Ar ratio. Electrical characterization has been also performed in controlled atmosphere in order to investigate the influence of NO2 oxidizing gas on the material conductance as a function of deposition parameters. A strict relation between structure, morphology and resistance variation in controlled atmosphere has been observed. © 1997 American Institute of Physics.
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73.61.Le Other inorganic semiconductors
72.80.Ga Transition-metal compounds
81.15.Cd Deposition by sputtering
68.55.-a Thin film structure and morphology
72.20.Fr Low-field transport and mobility; piezoresistance
07.07.Df Sensors (chemical, optical, electrical, movement, gas, etc.); remote sensing

Schottky barrier formation in a Au/Si nanoscale system: A local density approximation study

V. G. Zavodinsky and I. A. Kuyanov

J. Appl. Phys. 81, 2715 (1997); http://dx.doi.org/10.1063/1.364298 (5 pages) | Cited 2 times

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First-principles local density cluster calculations show that a Schottky junction may be formed in a nanoscale Au–Si(111) systems. The calculated Schottky barrier height value depends on the nanosystem’s geometry and varies from 0.5 to 1.35 eV. The total energy calculations show that the metallic gold/silicon system is unstable if the thickness of the gold is more than 2–3 monolayers. © 1997 American Institute of Physics.
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73.20.At Surface states, band structure, electron density of states
73.30.+y Surface double layers, Schottky barriers, and work functions
73.40.Ns Metal-nonmetal contacts
72.80.Cw Elemental semiconductors

Low resistance Pd/Zn/Pd ohmic contact to p-In0.82Ga0.18As0.39P0.61

Moon-Ho Park, L. C. Wang, and C. J. Palmstrøm

J. Appl. Phys. 81, 2720 (1997); http://dx.doi.org/10.1063/1.363974 (5 pages) | Cited 2 times

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We report on the investigation of a low resistance Pd/Zn/Pd contact to p-InGaAsP (λ=1.14 μm). The contact had a minimum contact resistivity of ∼3×10−7 Ω cm2 to the substrate doped to 2×1018 cm−3. The samples showed rather uniform surface and interfacial morphologies. X-ray studies showed the formation of a PdZn phase for samples annealed below 400 °C and this phase started to decompose at temperatures higher than 400 °C. Pd-III compounds (Pd2Ga5 and PdIn3) also started to form for annealing temperatures higher than 400 °C. The ohmic behavior can be understood in terms of the decomposition of the PdZn phase and the formation of Pd-III compounds for samples annealed at 400 °C or higher. The thermal stability of this contact at 400 °C was found to be stable, which is important for device applications. © 1997 American Institute of Physics.
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73.40.Ns Metal-nonmetal contacts
73.40.Cg Contact resistance, contact potential
68.35.B- Structure of clean surfaces (and surface reconstruction)
68.35.Ct Interface structure and roughness
61.72.Cc Kinetics of defect formation and annealing

A rectifying tungsten-molybdenum foil for positron remoderation

L. V. Jørgensen, A. van Veen, H. Schut, and J. Chevallier

J. Appl. Phys. 81, 2725 (1997); http://dx.doi.org/10.1063/1.363975 (5 pages) | Cited 2 times

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We report the use of a layered foil as a positron rectifying device for transmission geometry positron moderation and remoderation, thereby increasing the efficiency of such devices. Positron transmission through foils consisting of a 10 nm W layer on top of a 100 nm Mo foil has been measured. The measurements are compared with similar results for a 100 nm W foil. A strong rectifying effect with a forward to reverse current ratio of more than 10 is observed making this type of well matched layered foils an obvious candidate for positron remoderation. Retarding energy spectra of the transmitted positrons were obtained and measurements of Doppler broadening and surface branching ratios were performed to further characterize the foils. The obtained transmission results again reveal the discrepancy in positron implantation profiles for thin foils between experiments and existing theory. © 1997 American Institute of Physics.
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29.27.Eg Beam handling; beam transport
41.75.Fr Electron and positron beams

Quadratic power corrections to the dynamic magnetization using the transverse magnetostatic wave-optical interaction

A. Prabhakar and D. D. Stancil

J. Appl. Phys. 81, 2730 (1997); http://dx.doi.org/10.1063/1.363970 (6 pages)

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A microstrip T-transducer excites forward volume magnetostatic waves (MSWs) in a [BiLu]3Fe5O12 film. An optical beam is edge coupled into the film and the transverse MSW–optical interaction is observed at high microwave power levels. Using the coupled mode equations, we demonstrate that a T-transducer causes the intensity of the diffracted beam to be a product of terms involving the magneto-optic coupling coefficient (κ) and the phase mismatch between the optical guided modes and the MSWs. Taylor series expansions for κ and the MSW wave number (β) are used to obtain an analytic expression for the MSW–optical interaction. The dependence on β causes a shift in the interaction spectrum with increasing power. After correcting for this shift, the residual dependence on power is attributed to a quadratic correction to the dynamic magnetization which in turn affects κ. We demonstrate how the quadratic dependence plays an important role in accurately determining an expansion for the MSW dispersion relation. © 1997 American Institute of Physics.
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75.30.Ds Spin waves
75.70.Ak Magnetic properties of monolayers and thin films
78.20.Ls Magneto-optical effects
78.66.Nk Insulators
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects

Nanocrystalline Fe–M–B–Cu (M=Zr,Nb) alloys with improved soft magnetic properties

Akihiro Makino, Teruo Bitoh, Akihisa Inoue, and Tsuyoshi Masumoto

J. Appl. Phys. 81, 2736 (1997); http://dx.doi.org/10.1063/1.363976 (4 pages) | Cited 13 times

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The soft magnetic properties of the nanocrystalline Fe–M–B (M=Zr,Nb) alloys, which exhibit a high saturation flux density (Bs) above 1.5 T as well as a high effective permeability (μe) above 30 000 at 1 kHz, were found to be improved by adding small amounts of Cu and by optimizing the chemical composition. The addition of Cu to the alloys decreases the bcc grain size. The excellent soft magnetic properties (a high μe of 100 000 at 1 kHz combined with a high Bs of 1.53 T) can be achieved in the region where small grain size, as well as nearly zero-magnetostriction are obtained, which is attained in the compositional range around Fe84Nb3.5Zr3.5B8Cu1. The soft magnetic properties can be further improved by low temperature annealing before the crystallization treatment, probably as a result of a decreased grain size distribution in the crystallized state. Consequently, the μe reaches the maximum value of 120 000 for the nanocrystalline Fe84Nb3.5Zr3.5B8Cu1 alloy. © 1997 American Institute of Physics.
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75.50.Kj Amorphous and quasicrystalline magnetic materials
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
61.46.-w Structure of nanoscale materials
75.50.Bb Fe and its alloys

Deposition of high-quality NiMnSb magnetic thin films at moderate temperatures

J. A. Caballero, Y. D. Park, A. Cabbibo, J. R. Childress, F. Petroff, and R. Morel

J. Appl. Phys. 81, 2740 (1997); http://dx.doi.org/10.1063/1.363977 (5 pages) | Cited 26 times

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Thin films of the ferromagnetic Heusler alloy NiMnSb, of interest for magnetic multilayer devices because of their predicted half-metallic (i.e., 100% spin-polarized) transport properties, have been successfully deposited by rf magnetron sputtering from a single composite target. A novel combination of low argon gas pressure, low deposition rates, and moderate substrate temperatures (250–350 °C) are shown to result in high-quality, low-roughness polycrystalline films of the C1b-type crystal structure, with thicknesses as low as 100 Å, without the need for any post-deposition annealing. The structural properties of these films, determined by x-ray diffraction and atomic force microscopy are presented as a function of deposition conditions. The magnetic properties and resistivity are consistent with bulk MiMnSb, which suggests that they will be effective as spin-polarized conducting layers in multilayer thin-film structures. © 1997 American Institute of Physics.
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81.15.Cd Deposition by sputtering
81.05.Bx Metals, semimetals, and alloys
68.55.-a Thin film structure and morphology
75.70.Ak Magnetic properties of monolayers and thin films
75.50.Cc Other ferromagnetic metals and alloys
73.61.At Metal and metallic alloys

Magnetic exchange coupling in (Dy,Tb)FeCo magneto-optical recording films

Wein-Kuen Hwang and Han-Ping D. Shieh

J. Appl. Phys. 81, 2745 (1997); http://dx.doi.org/10.1063/1.363978 (4 pages) | Cited 2 times

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The required bias field of a sperimagnetic film is governed by a finite exchange coupling coefficient (λ) mainly determined by the subnetwork coupling. From the study of a series of (Dy,Tb)FeCo films at compensation composition, it is found that λ is mainly determined by the concentration of the rare earth components. Moreover, the exchange integral between rare earth and transition metal subnetworks can be derived from λ so that the number of uncertain parameters for mean field modeling is reduced. Accordingly, the bias field required for magneto-optical recording is mainly proportional to λ that can be obtained quantitatively from either measurement and/or mean field modeling. © 1997 American Institute of Physics.
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75.70.Ak Magnetic properties of monolayers and thin films
85.70.Sq Magnetooptical devices
75.30.Et Exchange and superexchange interactions
75.50.Ss Magnetic recording materials
75.50.Gg Ferrimagnetics
75.50.Kj Amorphous and quasicrystalline magnetic materials

Size dependence of microwave permeability of spherical ferromagnetic particles

G. Viau, F. Fiévet-Vincent, F. Fiévet, P. Toneguzzo, F. Ravel, and O. Acher

J. Appl. Phys. 81, 2749 (1997); http://dx.doi.org/10.1063/1.363979 (6 pages) | Cited 51 times

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Spherical, monodispersed, ferromagnetic, metallic particles of different compositions were obtained by the polyol process with a mean radius ranging from 30 nm to 1 μm. The microwave permeability of metallic particles-dielectric matrix composites were studied in the range of 0.1–18 GHz. In the wide particle size range investigated, a size dependence of the dynamic permeability was observed. Whereas the permeability of micrometer-sized particles shows a single resonance band, the permeability of submicrometer-sized particles exhibits several narrow resonance bands which are shifted to high frequencies with decreasing particle size. This latter behavior was found to be in qualitative agreement with the exchange resonance modes calculated by Aharoni. That theory, however, gives an R−2 dependence on particle radius for the resonance frequency instead of the R−0.66 dependence observed experimentally. © 1997 American Institute of Physics.
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75.50.Tt Fine-particle systems; nanocrystalline materials
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.30.Et Exchange and superexchange interactions

Properties of ultra-thin lead zirconate titanate thin films prepared by ozone jet reactive evaporation

Kazuyoshi Torii, Hirosi Kawakami, Hiroshi Miki, Keiko Kushida, and Yoshihisa Fujisaki

J. Appl. Phys. 81, 2755 (1997); http://dx.doi.org/10.1063/1.363980 (5 pages) | Cited 9 times

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Lead zirconate titanate (PZT) thin films were prepared by reactive coevaporation with high-concentration ozone. PZT thin films that demonstrate the highest charge storage density (280 fC/μm2 at 1.5 V for 75-nm-thick film) yet reported have been fabricated. No fatigue was observed after 1011 polarization switching cycles even though a Pt electrode is used. A low leakage current of <10−7 A/cm2 at 1.5 V was attained. These PZT films are promising candidates of an alternative capacitor dielectric for dynamic random access memory (DRAM) and ferroelectric nonvolatile memories. © 1997 American Institute of Physics.
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81.15.Jj Ion and electron beam-assisted deposition; ion plating
77.80.-e Ferroelectricity and antiferroelectricity
77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
85.50.-n Dielectric, ferroelectric, and piezoelectric devices
77.22.Ej Polarization and depolarization
77.55.-g Dielectric thin films

Temperature dependence of elastic, dielectric, and piezoelectric properties of “single crystalline’’ films of vinylidene fluoride trifluoroethylene copolymer

Kenji Omote, Hiroji Ohigashi, and Keiko Koga

J. Appl. Phys. 81, 2760 (1997); http://dx.doi.org/10.1063/1.364300 (10 pages) | Cited 63 times

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Elastic, dielectric, and piezoelectric constant matrix elements of a “single crystalline’’ (SC) film of vinylidene fluoride trifluoroethylene copolymer, P(VDF/TrFE), in which the orthorhombic [001] and [110] axes of fully extended chain crystals are preferentially oriented parallel to the stretching axis and normal to the surface, respectively, were measured at temperatures ranging from 10 K to the Curie point (402–404 K) by using a piezoelectric resonance method. All of the electromechanical coupling factors (k31, k32, k33, k24, and k15) are larger than those of conventional lamellar crystalline films. Some of the matrix elements for a P(VDF/TrFE) single crystal are derived from the measured values of constant matrix elements for the SC film. Some features characteristic of the SC film are revealed. The SC film has a large Young’s modulus for the stretching direction (1/s11) (121 GPa at 10 K). The properties related to the molecular motions along the chain axis, such as 1/s11, shear stiffness constant c55, shear piezoelectric constant e15, etc., exhibit strong relaxations around 250 K. The origin of these relaxations in the crystalline phase is discussed. © 1997 American Institute of Physics.
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77.65.Bn Piezoelectric and electrostrictive constants
77.80.-e Ferroelectricity and antiferroelectricity
77.22.Ch Permittivity (dielectric function)
62.20.D- Elasticity
61.41.+e Polymers, elastomers, and plastics
68.55.-a Thin film structure and morphology
77.84.Jd Polymers; organic compounds
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