jap banner
  • Volume/Page
  • Keyword
  • DOI
  • Citation
  • Advanced
   
 
 
 

Flickr Twitter iResearch App Facebook

BROWSE VOLUMES

Year Range: 
Search Issue | RSS Feeds RSS
Previous Issue

15 Dec 2004

Volume 96, Issue 12, pp. 6959-7777

Page 3 of 6 Pages Previous Page Next Page | Jump to Page
back to top
RSS Feeds

Transport properties of electron-beam and photo excited carriers in high-quality single-crystalline chemical-vapor-deposition diamond films

T. Teraji, S. Yoshizaki, S. Mitani, T. Watanabe, and T. Ito

J. Appl. Phys. 96, 7300 (2004); http://dx.doi.org/10.1063/1.1805723 (6 pages) | Cited 23 times

Online Publication Date: 2 December 2004

Full Text: Read Online (HTML) | Download PDF

Show Abstract
We have investigated transport properties of carriers excited in high-quality homoepitaxial diamond (100) films by 5.6 eV photons or 15 keV electrons. The high-quality single-crystalline diamond films were homoepitaxially grown on type-Ib diamond substrates at a rate of 2.5 μm∕h by high-power microwave-plasma chemical-vapor-deposition (MPCVD). In cathodoluminescence (CL) measurements, strong free-exciton recombination emissions were observed at room temperature from the almost whole specimen surface, indicating the grown films have substantially high quality. It is found through an analysis of the visible emission band originating from the type-Ib substrate that decay constants estimated for excited carriers were ∼5 μm in the depth direction. This is consistent with the fact that the intensity of spotlike CL images varied with an exponential function of the lateral length. From transient photocurrent measurements using ultrashort pulse laser excitations, decay times τ for the present high-quality diamond were estimated to be 15 and 100 ns for electrons and holes, respectively. Charge collection distances at an electric field E of 830 V∕cm were deduced to be ∼190 μm and over 1.2 mm for electrons and holes, respectively. The former may give a high electron drift mobility of μ∼1600 cm2∕Vs while the diffusion coefficients estimated for electrons are 55±14 cm2∕V s, which is comparable with or even higher than those of Si. These physical quantities demonstrate high quality of the diamond films grown by means of the high-power MPCVD method.
Show PACS
68.55.A- Nucleation and growth
73.50.Pz Photoconduction and photovoltaic effects
73.61.Ng Insulators
73.50.Dn Low-field transport and mobility; piezoresistance
73.50.Gr Charge carriers: generation, recombination, lifetime, trapping, mean free paths
78.60.Hk Cathodoluminescence, ionoluminescence
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
71.35.-y Excitons and related phenomena

Electrical transport properties of microcrystalline silicon grown by plasma enhanced chemical vapor deposition

Nicola Pinto, Marco Ficcadenti, Lorenzo Morresi, Roberto Murri, Giuseppina Ambrosone, and Ubaldo Coscia

J. Appl. Phys. 96, 7306 (2004); http://dx.doi.org/10.1063/1.1812818 (6 pages) | Cited 7 times

Online Publication Date: 2 December 2004

Full Text: Read Online (HTML) | Download PDF

Show Abstract
The dark conductivity and Hall mobility of hydrogenated silicon films deposited varying the silane concentration f=SiH4∕(SiH4+H2) in a conventional plasma enhanced chemical vapor deposition system have been investigated as a function of temperature, taking into account their structural properties. The electrical properties have been studied in terms of a structural two-phase model. A clear transition from the electrical transport governed by a crystalline phase, in the range 1%⩽f⩽3%, to that controlled by an amorphous phase, for f>3%, has been evidenced. Some metastable effects of the dark conductivity have been noticed.
Show PACS
73.61.Jc Amorphous semiconductors; glasses
73.61.Cw Elemental semiconductors
61.43.Dq Amorphous semiconductors, metals, and alloys
73.50.Jt Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects)
68.55.-a Thin film structure and morphology
68.55.A- Nucleation and growth
81.05.Gc Amorphous semiconductors
81.05.Cy Elemental semiconductors
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)

Gated four-probe measurements on pentacene thin-film transistors: Contact resistance as a function of gate voltage and temperature

Paul V. Pesavento, Reid J. Chesterfield, Christopher R. Newman, and C. Daniel Frisbie

J. Appl. Phys. 96, 7312 (2004); http://dx.doi.org/10.1063/1.1806533 (13 pages) | Cited 118 times

Online Publication Date: 2 December 2004

Full Text: Read Online (HTML) | Download PDF

Show Abstract
We describe gated four-probe measurements designed to measure contact resistance in pentacene-based organic thin-film transistors (OTFTs). The devices consisted of metal source and drain electrodes contacting a 300-math-thick pentacene film thermally deposited on Al2O3 or SiO2 dielectrics with a p-doped Si substrate serving as the gate electrode. Voltage-sensing leads extending into the source-drain channel were used to monitor potentials in the pentacene film while passing current during drain voltage (VD) or gate voltage (VG) sweeps. We investigated the potential profiles as a function of contact metallurgy (Pt, Au, Ag, and Ca), substrate chemistry, VG, and temperature. The contact-corrected linear hole mobilities were as high as 1.75 cm2∕V s and the film sheet resistance and specific contact resistance were as low as 600 kΩ∕□ and 1.3 kΩ-cm, respectively, at high gate voltages. In the temperature range of 50–200 K, the pentacene OTFTs displayed an activated behavior with activation energies of 15–30 meV. Importantly, the activation energy associated with the contact resistance showed no dependence on contact metal type at high gate voltage. Also, the activation energies of the contact resistance and film resistance were approximately the same. Above approximately 200 K and below 50 K, the mobility was essentially temperature independent.
Show PACS
85.30.Tv Field effect devices
73.40.Cg Contact resistance, contact potential
73.61.Ph Polymers; organic compounds
85.65.+h Molecular electronic devices

Ohmic contacts to p-type Al0.45Ga0.55N

B. A. Hull, S. E. Mohney, U. Chowdhury, and R. D. Dupuis

J. Appl. Phys. 96, 7325 (2004); http://dx.doi.org/10.1063/1.1814169 (7 pages) | Cited 8 times

Online Publication Date: 2 December 2004

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Ni, Pd, and Au Ohmic contacts to p-Al0.45Ga0.55N have been examined. We have observed that annealing the contacts in excess of 800 °C is required to minimize the contact resistivity. However, the Pd and Au contacts annealed in excess of 700 °C, which showed much better transport properties than Ni contacts annealed at the same temperatures, suffered from a rapid photoinduced degradation of both the current-voltage characteristics of the contacts and of the sheet resistance of the p-Al0.45Ga0.55N itself. This degradation was greatly reduced by passivating the p-Al0.45Ga0.55N surface with a SiNx film. A hypothesis is presented to describe the observed degradation.
Show PACS
81.05.Ea III-V semiconductors
73.40.Ns Metal-nonmetal contacts
73.61.Ey III-V semiconductors
73.40.Cg Contact resistance, contact potential
61.72.Cc Kinetics of defect formation and annealing
81.65.Rv Passivation

Deep-level-transient spectroscopy of heavily Al-doped ZnSe layers grown by molecular-beam epitaxy

D. C. Oh, T. Takai, T. Hanada, M. W. Cho, T. Yao, J. S. Song, J. H. Chang, and F. Lu

J. Appl. Phys. 96, 7332 (2004); http://dx.doi.org/10.1063/1.1814170 (6 pages) | Cited 4 times

Online Publication Date: 2 December 2004

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Using deep-level-transient spectroscopy, we have investigated deep levels in heavily Al-doped ZnSe layers grown by molecular-beam epitaxy. The Al concentration of the ZnSe layers lies in the range of 5×1018–9×1018 cm−3. The ZnSe:Al layers exhibit two electron-trap centers with the thermal activation energies of 0.16 eV (ND1) and 0.80 eV (ND2). ND2 is a dominant trap center with a trap density of 3×1016 cm−3, while the trap density of ND1 is estimated to be 2×1015 cm−3. However, ND2 shows anomalous behaviors, different from isolated point defects, in the following points: (1) the emission peak of ND2 moves to the low temperature side with increasing filling pulse duration; (2) the emission peak of ND2 is broader than theoretically calculated one for an isolated point defect; and (3) the capacitance-transient curve is nonexponential. It is observed by high-resolution x-ray diffraction that heavy Al doping results in the relaxation and plastic deformation of the ZnSe lattice. These behaviors can be ascribed to extended defects with a broad energy spectrum. By assuming a Gaussian distribution of deep levels due to extended defect, the broad emission peak is successfully simulated.
Show PACS
71.55.Gs II-VI semiconductors
61.72.uj III-V and II-VI semiconductors
73.61.Ga II-VI semiconductors
73.50.Gr Charge carriers: generation, recombination, lifetime, trapping, mean free paths
73.50.Dn Low-field transport and mobility; piezoresistance
61.72.Nn Stacking faults and other planar or extended defects
81.40.Lm Deformation, plasticity, and creep
62.20.F- Deformation and plasticity

Unusual thermoelectric behavior of packed crystalline granular metals

M. Ausloos, M. Pȩkala, J. Latuch, J. Mucha, Ph. Vanderbemden, B. Vertruyen, and R. Cloots

J. Appl. Phys. 96, 7338 (2004); http://dx.doi.org/10.1063/1.1808248 (8 pages) | Cited 3 times

Online Publication Date: 2 December 2004

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Loosely packed granular materials are intensively studied nowadays. Electrical and thermal transport properties should reflect the granular structure, as well as intrinsic properties. We have compacted crystalline CaAl-based metallic grains and studied the electrical resistivity and the thermoelectric power as a function of temperature (T) from 15 to 300 K. Both properties show three regimes as a function of temperature. It should be pointed out: (i) The electrical resistivity continuously decreases between 15 and 235 K, (ii) with various dependencies, e.g., ≃T−3∕4 at low T, while (iii) the thermoelectric power (TEP) is positive, (iv) shows a bump near 60 K, and (v) presents a rather unusual square root of temperature dependence at low temperature. It is argued that these three regimes indicate a competition between geometric and thermal processes—for which a theory seems to be missing in the case of TEP. The microchemical analysis results are also reported, indicating a complex microstructure inherent to the phase diagram peritectic intricacies of this binary alloy.
Show PACS
72.15.Eb Electrical and thermal conduction in crystalline metals and alloys
72.15.Jf Thermoelectric and thermomagnetic effects
81.30.Bx Phase diagrams of metals, alloys, and oxides
82.80.-d Chemical analysis and related physical methods of analysis

Determination of densities and energy levels of donors in free-standing undoped 3C–SiC epilayers with thicknesses of 80 μm

Hideharu Matsuura, Hiroyuki Nagasawa, Kuniaki Yagi, and Takamitsu Kawahara

J. Appl. Phys. 96, 7346 (2004); http://dx.doi.org/10.1063/1.1814805 (6 pages) | Cited 6 times

Online Publication Date: 2 December 2004

Full Text: Read Online (HTML) | Download PDF

Show Abstract
The densities and energy levels of donors in free-standing undoped 3C–SiC epilayers with the thicknesses of ∼80 μm are investigated from the temperature dependence of the electron concentration n(T) obtained by Hall-effect measurements. Although in the analysis of n(T) many researchers usually assume that only one type of donor species is included in n-type 3C–SiC, no one knows whether this assumption is correct or not. In order to determine the densities and energy levels using n(T) without any assumptions regarding donor species, the graphical peak analysis method called free carrier concentration spectroscopy is applied. Three types of donor species are detected in these epilayers. These donor densities can be reduced to <5×1015 cm−3 by growing 3C–SiC epilayers on undulant Si substrate. Moreover, the dependence of each donor level on a total donor density is investigated, which is used in 3C–SiC device simulation.
Show PACS
71.55.Ht Other nonmetals
73.61.Le Other inorganic semiconductors
73.50.Jt Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects)
73.50.Dn Low-field transport and mobility; piezoresistance

Electrostatic cross-talk between quantum dot and quantum point contact charge read-out in few-electron quantum dot circuits

L.-X. Zhang and J. P. Leburton

J. Appl. Phys. 96, 7352 (2004); http://dx.doi.org/10.1063/1.1814811 (5 pages) | Cited 1 time

Online Publication Date: 2 December 2004

Full Text: Read Online (HTML) | Download PDF

Show Abstract
We investigate by numerical simulation the effect of electrostatic coupling between a quantum point contact (QPC) detector of various geometries and a planar double quantum dot in a few-electron quantum dot circuit. Our simulation is based on solving coupled Kohn-Sham and Poisson equations self-consistently by the finite element method. We use the Slater formula to determine the first electron charging bias point of the plunger gate, and give the corresponding variation of the QPC conductance as a function of the QPC gate bias at that particular point, which we interpret as the detector sensitivity. For all QPC designs, we show that the charging bias point of the plunger gate decreases with increasing QPC gate bias. This effect is enhanced for designs wherein large QPC detection sensitivity is found.
Show PACS
85.35.Ds Quantum interference devices
85.30.De Semiconductor-device characterization, design, and modeling
73.40.Kp III-V semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions

Metastable boron active concentrations in Si using flash assisted solid phase epitaxy

S. H. Jain, P. B. Griffin, J. D. Plummer, S. Mccoy, J. Gelpey, T. Selinger, and D. F. Downey

J. Appl. Phys. 96, 7357 (2004); http://dx.doi.org/10.1063/1.1814792 (4 pages) | Cited 13 times

Online Publication Date: 2 December 2004

Full Text: Read Online (HTML) | Download PDF

Show Abstract
There has been considerable interest recently, in the formation of the source drain junctions of metal oxide semiconductor transistors using solid phase epitaxy (SPE) to activate the dopants rather than a traditional high temperature anneal. Previous studies have shown that this method results in high dopant activation as well as shallow junctions (due to the small thermal budget). In this we study the effect the temperature of SPE regrowth has on the boron activation. We find that boron activation has a monotonically increasing dependence on the temperature. Significantly, we show that by carrying out the SPE regrowth at temperatures above 1050 °C, it is possible to obtain active concentrations well above the electrical solubility limits.
Show PACS
81.05.Cy Elemental semiconductors
68.55.A- Nucleation and growth
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
61.72.S- Impurities in crystals
81.15.Np Solid phase epitaxy; growth from solid phases
81.40.Gh Other heat and thermomechanical treatments

Contact electrification of high-K oxides studied by electrostatic force microscopy

J. Lambert, M. Saint-Jean, and C. Guthmann

J. Appl. Phys. 96, 7361 (2004); http://dx.doi.org/10.1063/1.1815386 (9 pages) | Cited 4 times

Online Publication Date: 2 December 2004

Full Text: Read Online (HTML) | Download PDF

Show Abstract
In order to clarify the mechanisms of charge transfer on insulating surfaces by contact electrification, we performed charge-transfer experiments on high-K oxides using the tip of an electrostatic force microscope. In particular, we investigated the influence of the applied voltage between the tip and the surface and the contact duration on the amount of transferred charges on Al2O3. The electronic motion in the insulating material is analyzed in terms of hopping processes assisted by the electric field created by the tip inside the oxide. We show that this electric field must be described by a three-dimensional model. In this frame, the transfer mechanism is analyzed as an instantaneous wetting of the surface by the charges—the surface being a region of large trap concentration—followed by a progression of the charges inside the oxide.
Show PACS
77.84.-s Dielectric, piezoelectric, ferroelectric, and antiferroelectric materials
68.37.Ps Atomic force microscopy (AFM)
82.30.Fi Ion-molecule, ion-ion, and charge-transfer reactions
72.20.Ee Mobility edges; hopping transport
68.08.Bc Wetting

Exchange-enhanced g‐factors in an Al0.25Ga0.75N∕GaN two-dimensional electron system

K. S. Cho, Tsai-Yu Huang, Chao-Ping Huang, Yi-Hsing Chiu, C.-T. Liang, Y. F. Chen, and Ikai Lo

J. Appl. Phys. 96, 7370 (2004); http://dx.doi.org/10.1063/1.1815390 (4 pages) | Cited 9 times

Online Publication Date: 2 December 2004

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Low-temperature magnetotransport measurements were performed on an Al0.25Ga0.75N∕GaN two-dimensional electron system. In this system, we observe Shubnikov-de Haas (SdH) oscillations in a perpendicular magnetic field B. By measuring the positions of a pair of spin-split SdH maxima, we are able to estimate the g‐factors at different Landau level (LL) indices. We find the g‐factor is enhanced over its bulk value in GaN (≅2) due to many-body exchange interactions. Moreover, the measured g‐factor increases with decreasing LL index, indicating that many-body electron–electron interactions become stronger as the number of occupied LLs decreases. Our results suggest that the exchange energy Eex shows an approximately linear B dependence.
Show PACS
73.20.Qt Electron solids
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
71.18.+y Fermi surface: calculations and measurements; effective mass, g factor
71.70.Di Landau levels
71.70.Gm Exchange interactions
71.45.Gm Exchange, correlation, dielectric and magnetic response functions, plasmons
73.40.Kp III-V semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
73.50.Jt Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects)

Analytical k⋅p method: Anisotropic optical matrix elements in (11N)-oriented quantum wells

Chun-Nan Chen

J. Appl. Phys. 96, 7374 (2004); http://dx.doi.org/10.1063/1.1818352 (5 pages) | Cited 11 times

Online Publication Date: 2 December 2004

Full Text: Read Online (HTML) | Download PDF

Show Abstract
This paper develops a k⋅p method with analytical expressions to investigate the optical anisotropy of (11N)-oriented In0.53Ga0.47As∕InP quantum wells. The proposed method is not only more straightforward than the conventional k⋅p method, but also more efficient. The present results reveal that in-plane anisotropy is associated with low-symmetry crystal microstructures. Hence, of the various (11N)-oriented quantum wells considered in the present study, the low-symmetry (110) sample exhibits the most obvious anisotropy, while the high-symmetry (001) and (111) samples exhibit isotropy.
Show PACS
73.21.Fg Quantum wells
71.15.Ap Basis sets (LCAO, plane-wave, APW, etc.) and related methodology (scattering methods, ASA, linearized methods, etc.)

The Meyer-Neldel rule for diodes in forward bias

Ralf Widenhorn, Michael Fitzgibbons, and Erik Bodegom

J. Appl. Phys. 96, 7379 (2004); http://dx.doi.org/10.1063/1.1818353 (4 pages) | Cited 9 times

Online Publication Date: 2 December 2004

Full Text: Read Online (HTML) | Download PDF

Show Abstract
We analyzed the temperature dependence of the forward current of a silicon diode. Instead of representing the data in the ordinarily used current versus voltage graph, the currents are plotted for different voltages as a function of the inverse temperature. The constant voltage curves can be fitted linearly and the extrapolations of the fits seem to merge to one common focal point. Hence, we demonstrate that a real diode follows the Meyer-Neldel rule (MNR). It is shown that the MNR is due to a shift of the current from ideal-diode to high-injection-diode behavior. We will argue that the merging of the different Arrhenius plots toward one focal point, and hence a MNR, can be the result of various mechanisms. The general requirements to observe a MNR are not very restrictive. It is therefore not surprising that the MNR has been observed in a multitude of systems. The origin that gives rise to the MNR can be manifold and allows for different models to explain its occurrence.
Show PACS
85.30.Kk Junction diodes
85.30.De Semiconductor-device characterization, design, and modeling

Structural, electrical transport, magnetization, and 1∕f noise studies in 200 MeV Ag ion irradiated La0.7Ce0.3MnO3 thin films

Ravi Kumar, R. J. Choudhary, S. I. Patil, Shahid Husain, J. P. Srivastava, S. P. Sanyal, and S. E. Lofland

J. Appl. Phys. 96, 7383 (2004); http://dx.doi.org/10.1063/1.1818719 (5 pages) | Cited 15 times

Online Publication Date: 2 December 2004

Full Text: Read Online (HTML) | Download PDF

Show Abstract
The effect of 200 MeV Ag ion irradiation on structural, electrical transport, magnetization, and low-frequency conduction noise properties of electron-doped La0.7Ce0.3MnO3 thin films have been investigated. The as-grown thin films show c-axis epitaxial structure along with a small amount of unreacted CeO2 phase. After the irradiation, at the lowest fluence both the magnetization and metal-insulator transition temperature increase. Further increase in fluence reduces the metal-insulator transition temperature and leads to larger resistivity; however, the unreacted phase of CeO2 disappears in the x-ray diffraction pattern. On the other hand, the normalized electrical noise is greatly enhanced even at the lowest nonzero fluence. Surprisingly the conducting noise in the irradiated samples is much higher in the metallic state than in the semiconducting one. The observed modifications in structural, electrical, magnetic, and noise properties of 200 MeV Ag ion irradiated La0.7Ce0.3MnO3 thin films have been explained on the basis of effects of the presence of swift heavy-ion irradiation-induced strain and defects.
Show PACS
68.55.-a Thin film structure and morphology
75.70.Ak Magnetic properties of monolayers and thin films
73.50.Td Noise processes and phenomena
61.80.Jh Ion radiation effects
61.82.Ms Insulators
71.30.+h Metal-insulator transitions and other electronic transitions
73.61.Ng Insulators
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects

Thermal activation of As implanted in bulk Si and separation by implanted oxygen

M. Dalponte, H. Boudinov, L. V. Goncharova, D. Starodub, E. Garfunkel, and T. Gustafsson

J. Appl. Phys. 96, 7388 (2004); http://dx.doi.org/10.1063/1.1776319 (4 pages)

Online Publication Date: 2 December 2004

Full Text: Read Online (HTML) | Download PDF

Show Abstract
We have studied arsenic (As) diffusion and its electrical activation in two different types of silicon substrates: bulk Si and separation by implanted oxygen (SIMOX) wafers. Both substrates were implanted with a dose of 5×1014 cm−2 As+ at 20 keV. The samples were annealed and physical characterization was performed with secondary ion mass spectrometry (SIMS), Rutherford backscattering spectrometry, and medium energy ion scattering. The electrical properties of the film were extracted by Hall measurements. The SIMS results showed a lower dopant outdiffusion loss to the atmosphere during annealing in the SIMOX samples. The electrical results for the SIMOX samples were also superior to those of bulk Si due to the higher dopant retention, likely the result of a higher concentration of vacancies, which in turn increases the relative fraction of As which is activated (in substitutional sites). The net effect was a higher sheet carrier concentration and lower sheet resistance in the SIMOX samples. The implantation damage removal was superior in SIMOX samples compared to bulk Si ones.
Show PACS
73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
73.61.Cw Elemental semiconductors
61.72.uf Ge and Si
61.72.S- Impurities in crystals
61.80.Jh Ion radiation effects
66.30.H- Self-diffusion and ionic conduction in nonmetals
61.72.Cc Kinetics of defect formation and annealing
61.72.J- Point defects and defect clusters
79.20.Rf Atomic, molecular, and ion beam impact and interactions with surfaces
73.50.Jt Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects)
back to top
RSS Feeds

Magnetic and transport properties of Ag∕Co90Fe10 granular multilayers

J. Milano, A. M. LLois, L. B. Steren, A. Butera, and J. Barnard

J. Appl. Phys. 96, 7392 (2004); http://dx.doi.org/10.1063/1.1810638 (7 pages) | Cited 3 times

Online Publication Date: 2 December 2004

Full Text: Read Online (HTML) | Download PDF

Show Abstract
We report experimental results on the magnetic and transport properties of Ag∕Co90Fe10 multilayers with variable Ag and Co90Fe10 thicknesses. The magnetism samples was characterized by magnetization measurements and ferromagnetic resonance spectroscopy. These measurements show that the magnetic layers are in general composed by single-domain particles and that the shape and the size of the magnetic clusters can be changed by using an applied magnetic field (Hdep) on deposition. The resistivity of these multilayered systems is described by a mixed model that includes current-in-plane and current perpendicular plane transport contributions. The transport model proposed to explain the experimental results emphasizes the role played by the magnetic entities on the scattering processes and strongly depends on the silver layer thickness. An electrical percolative transition is observed for samples grown at Hdep>Hdep* while the magnetic properties of these samples still show a granularlike behavior.
Show PACS
68.65.Ac Multilayers
75.50.Bb Fe and its alloys
75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
75.50.Tt Fine-particle systems; nanocrystalline materials
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.60.Ch Domain walls and domain structure
75.70.Kw Domain structure (including magnetic bubbles and vortices)
72.15.Gd Galvanomagnetic and other magnetotransport effects
73.43.Qt Magnetoresistance
76.50.+g Ferromagnetic, antiferromagnetic, and ferrimagnetic resonances; spin-wave resonance

Relation between exchange coupling and enhanced coercivity in the free layer of a patterned magnetic tunnel junction

CheolGi Kim, Chong-Oh Kim, Masakiyo Tsunoda, Migaku Takahashi, and Tomasz Stobiecki

J. Appl. Phys. 96, 7399 (2004); http://dx.doi.org/10.1063/1.1811776 (4 pages)

Online Publication Date: 2 December 2004

Full Text: Read Online (HTML) | Download PDF

Show Abstract
A magneto-optical Kerr effect system with a spatial resolution of 2 μm was used to measure the local M-H loops for the free layer of a magnetic tunnel junction with a structure of Ta∕Cu∕Ta∕NiFe∕Cu∕Mn75Ir25∕Co70Fe30∕Al2O3∕Co70Fe30∕Ta to investigate the exchange bias field HE and the coercivity HC for the free layer. The HE and HC measured along the direction of the free layer varied symmetrically with respect to the junction center. The measurements indicate that the enhanced HC correlated with HE, and HE could be reasonably explained by using an “orange-peel-type” coupling based on variations in the thickness of the pinned layer along the direction of the free layer. The variation in HE along the pinned-layer’s direction could be ascribed to that of the free-layer’s thickness, and the increase in HE at the junction edge along the pinned layer was due to a decrease in the thickness of the free layer near the edge. However, the nearly constant HC along the pinned layer indicates that the thickness of the free layer can be excluded from the mechanism for enhancing HC, which is a unique difference in the parameters involved in HE and HC, and in the mechanism for enhancing HC.
Show PACS
68.65.Ac Multilayers
75.50.Bb Fe and its alloys
75.50.Ee Antiferromagnetics
75.50.Vv High coercivity materials
75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
75.30.Et Exchange and superexchange interactions
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
78.20.Ls Magneto-optical effects

Columnar tilt and vortex stress in superconducting thin films of NdBa2Cu3O7−δ: Magnetization critical current-density measurements

Sanghamitra Khatua, P. K. Mishra, Ravi Kumar, D. C. Kundaliya, D. Buddhikot, R. Pinto, and S. K. Malik

J. Appl. Phys. 96, 7403 (2004); http://dx.doi.org/10.1063/1.1812351 (4 pages) | Cited 5 times

Online Publication Date: 2 December 2004

Full Text: Read Online (HTML) | Download PDF

Show Abstract
C-axis-oriented NdBa2Cu3O7−δ thin films (thickness ∼2000 math) on LaAlO3 substrates have been prepared and irradiated with Ag+14 (200 MeV) ions at different inclinations (θd=0°, 15°, 30°, and 45°) to the c axis. Magnetization-field hysteresis loops have been obtained on pristine and irradiated thin films at two different temperatures in applied magnetic fields up to 5 T. Estimates of the critical current density Jc(H,θ) and the volume pinning force Fp(H,θ) from the magnetization data reveal a strong dependence on track inclination. An increase and a subsequent saturation in Fp(H,θ), instead of the usual Gaussian peak around the equivalent matching field, Bϕ, is observed. It is suggested that this dependence of Jc (or Fp) on θd is a consequence of the effective modification of vortex pinning by tilted columnar defects.
Show PACS
74.78.-w Superconducting films and low-dimensional structures
74.72.-h Cuprate superconductors
74.25.Uv Vortex phases (includes vortex lattices, vortex liquids, and vortex glasses)
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
68.55.-a Thin film structure and morphology
74.25.Ha Magnetic properties including vortex structures and related phenomena
74.25.Sv Critical currents
61.80.Jh Ion radiation effects
61.72.Mm Grain and twin boundaries

Optical studies of zero-field magnetization of CdMnTe quantum dots: Influence of average size and composition of quantum dots

T. Gurung, S. Mackowski, H. E. Jackson, L. M. Smith, W. Heiss, J. Kossut, and G. Karczewski

J. Appl. Phys. 96, 7407 (2004); http://dx.doi.org/10.1063/1.1813622 (7 pages) | Cited 4 times

Online Publication Date: 2 December 2004

Full Text: Read Online (HTML) | Download PDF

Show Abstract
We show that through the resonant optical excitation of spin-polarized excitons into CdMnTe magnetic quantum dots (QD), we can induce a macroscopic magnetization of the Mn impurities. We observe very broad (4-meV linewidth) emission lines of single dots, which are consistent with the formation of strongly confined exciton magnetic polarons. Therefore, we attribute the optically induced magnetization of the magnetic dots to the formation of spin-polarized exciton magnetic polarons. We find that the photoinduced magnetization of magnetic polarons is weaker for larger dots which emit at lower energies within the QD distribution. We also show that the photoinduced magnetization is stronger for quantum dots with lower Mn concentration, which we ascribe to weaker Mn–Mn interaction between the nearest neighbors within the dots. Due to particular stability of the exciton magnetic polarons in QDs, where the localization of the electrons and holes is comparable to the magnetic exchange interaction, this optically induced spin alignment persists to temperatures as high as 160 K.
Show PACS
73.21.La Quantum dots
75.50.Pp Magnetic semiconductors
75.50.Dd Nonmetallic ferromagnetic materials
78.67.Hc Quantum dots
78.55.Et II-VI semiconductors
75.30.Et Exchange and superexchange interactions
75.25.-j Spin arrangements in magnetically ordered materials (including neutron and spin-polarized electron studies, synchrotron-source x-ray scattering, etc.)
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.30.Hx Magnetic impurity interactions
61.72.S- Impurities in crystals
73.20.Mf Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)
71.38.-k Polarons and electron-phonon interactions

Soft x-ray resonant magneto-optical Kerr effect as a depth-sensitive probe of magnetic heterogeneity: Its application to resolve helical spin structures using linear p polarization

Ki-Suk Lee, Sang-Koog Kim, and J. B. Kortright

J. Appl. Phys. 96, 7414 (2004); http://dx.doi.org/10.1063/1.1806535 (6 pages) | Cited 3 times

Online Publication Date: 2 December 2004

Full Text: Read Online (HTML) | Download PDF

Show Abstract
We have calculated the soft x-ray resonant Kerr intensities as a function of the incident grazing angle of linearly p-polarized waves from the model spin structures, where the chirality (handedness) of the spin spirals (twist in depth) in a magnetic layer and the periodicity of a unit spiral are designed to vary. Variations in the chirality and the periodicity lead to noticeable changes in the Kerr intensity versus the grazing angle, which is due not only to a large sensitivity of the Kerr intensity of the linear p polarization to both the magnitude and direction of the transverse components of magnetizations, but also to a large dependence of the depth sensitivity on the grazing angle at the resonance regions. The measurement and analysis of the specular Kerr intensity are relatively straightforward in determining the inhomogeneous spin structures in depth, compared to those of the Kerr rotation and ellipticity. This is proven to be a convenient and useful probe to determine the handedness of spin spiral structures, as well as to resolve the detailed magnetic heterostructures in depth in ultrathin-layered films.
Show PACS
68.65.Ac Multilayers
75.50.Bb Fe and its alloys
75.50.Dd Nonmetallic ferromagnetic materials
78.20.Ls Magneto-optical effects
75.25.-j Spin arrangements in magnetically ordered materials (including neutron and spin-polarized electron studies, synchrotron-source x-ray scattering, etc.)
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
61.80.Cb X-ray effects

Magnetic patterning using ion irradiation for highly ordered CoPt alloys with perpendicular anisotropy

M. Abes, J. Venuat, D. Muller, A. Carvalho, G. Schmerber, E. Beaurepaire, A. Dinia, and V. Pierron-Bohnes

J. Appl. Phys. 96, 7420 (2004); http://dx.doi.org/10.1063/1.1807522 (4 pages) | Cited 11 times

Online Publication Date: 2 December 2004

Full Text: Read Online (HTML) | Download PDF

Show Abstract
We used a combination of ion irradiation and e-beam lithography to magnetically pattern an ordered CoPt alloy with strong perpendicular magnetic anisotropy. Ion irradiation disorders the alloy and strongly reduces the magnetic anisotropy. Magnetic force microscopy showed a regular array of 1 μm2 square dots with perpendicular anisotropy separated by 1 μm large ranges with in-plane anisotropy. This is further confirmed by magnetic measurements, which showed that arrays protected by a 200 nm Pt layer present the same coercive field and the same perpendicular anisotropy as before irradiation. This is promising for applications in magnetic recording technologies.
Show PACS
75.50.Vv High coercivity materials
75.70.Ak Magnetic properties of monolayers and thin films
61.82.Bg Metals and alloys
68.55.-a Thin film structure and morphology
75.30.Gw Magnetic anisotropy
61.80.Jh Ion radiation effects
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
78.20.Ls Magneto-optical effects
85.40.Hp Lithography, masks and pattern transfer
68.37.Rt Magnetic force microscopy (MFM)

Effect of electrical bias on spin transport across a magnetic domain wall

M. Deutsch, G. Vignale, and M. E. Flatté

J. Appl. Phys. 96, 7424 (2004); http://dx.doi.org/10.1063/1.1815044 (4 pages) | Cited 4 times

Online Publication Date: 2 December 2004

Full Text: Read Online (HTML) | Download PDF

Show Abstract
We present a theory of the current-voltage characteristics of a magnetic domain wall between two highly spin-polarized materials, which takes into account the effect of the electrical bias on the spin-flip probability of an electron crossing the wall. We show that increasing the voltage reduces the spin-flip rate, and is therefore equivalent to reducing the width of the domain wall. As an application, we show that this effect widens the temperature window in which the operation of a unipolar spin diode is nearly ideal.
Show PACS
75.50.Dd Nonmetallic ferromagnetic materials
75.60.Ch Domain walls and domain structure
75.30.Et Exchange and superexchange interactions
75.30.Wx Spin crossover
72.25.Hg Electrical injection of spin polarized carriers
72.25.Rb Spin relaxation and scattering

Exchange bias in NiFe∕FeMn∕NiFe trilayers

V. K. Sankaranarayanan, S. M. Yoon, D. Y. Kim, C. O. Kim, and C. G. Kim

J. Appl. Phys. 96, 7428 (2004); http://dx.doi.org/10.1063/1.1815048 (7 pages) | Cited 31 times

Online Publication Date: 2 December 2004

Full Text: Read Online (HTML) | Download PDF

Show Abstract
NiFe∕FeMn∕NiFe trilayer structure forms an integral part of many conventional and tunneling magnetoresistance spin valve structures with FeMn antiferromagnetic layer. A systematic investigation of the exchange bias variations of the seed and top pinned NiFe layers in the NiFe∕FeMn∕NiFe trilayer structure is reported as a function of thickness of all the three constituting layers, in multilayers prepared by rf magnetron sputtering. X-ray diffraction patterns show the (111) texture for the NiFe and FeMn layers, necessary for the development of antiferromagnetic γ-fcc phase. In thickness variation studies of all the three magnetic layers, seed NiFe layer shows greater bias (150 Oe) than the top pinned NiFe layer (80 Oe only). The exchange bias shows the expected 1∕t behavior for increasing NiFe layer thickness after initial maxima at low thickness. In the FeMn antiferromagnet layer thickness variation on the other hand, the large bias values attained around 5 nm thickness is nearly retained up to a thickness of 25 nm and the bias for the top NiFe layer is again substantially lower. The greater bias observed for the seed NiFe layer in all the three thickness variation studies is attributed to its growth over a saturated (111) oriented NiFe seed layer, which induces formation of interfacial FeMn layers with a net parallel spin ordering, in presence of the constant applied field. On the other hand, at the top FeMn∕NiFe surface, the rigid FeMn surface with compensated bulk spin ordering formed already, is not easily biased and reoriented along the top NiFe layer, to develop as much parallel net spins in the antiferromagnetic material, and hence lower bias.
Show PACS
75.50.Ee Antiferromagnetics
75.50.Bb Fe and its alloys
75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
75.30.Et Exchange and superexchange interactions
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
73.50.Jt Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects)
75.25.-j Spin arrangements in magnetically ordered materials (including neutron and spin-polarized electron studies, synchrotron-source x-ray scattering, etc.)
68.65.Ac Multilayers
68.55.A- Nucleation and growth
81.15.Cd Deposition by sputtering
back to top
RSS Feeds

Tungsten bronze type dielectrics in SrO-Sm2O3-TiO2-Nb2O5 system and their dielectric anomaly

Y. H. Sun, X. M. Chen, and X. H. Zheng

J. Appl. Phys. 96, 7435 (2004); http://dx.doi.org/10.1063/1.1804246 (5 pages) | Cited 18 times

Online Publication Date: 2 December 2004

Full Text: Read Online (HTML) | Download PDF

Show Abstract
The dielectric behavior and the features of the diffused phase transition of the SrpSm6−pTi8−pNb2+pO30 (p=4,5) ceramics were investigated together with their structure. Both Sr5SmTi3Nb7O30 and Sr4Sm2Ti4Nb6O30 had tungsten bronze structure and weak ferroelectric nature. Though Sr5SmTi3Nb7O30 showed the diffused ferroelectrics phase transition, it was concluded that the transition was mainly the displacive ferroelectric phase transition. In Sr4Sm2Ti4Nb6O30, the Sr2+ ions and Sm3+ ions did not form an order structure and it showed a typical displacive ferroelectric phase transition. The dielectric anomaly was attributed to the different BO6 octahedral distortion.
Show PACS
77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
77.22.Ch Permittivity (dielectric function)
77.22.Gm Dielectric loss and relaxation
77.80.Dj Domain structure; hysteresis
77.80.B- Phase transitions and Curie point

High-frequency electron paramagnetic resonance investigation of the Fe3+ impurity center in polycrystalline PbTiO3 in its ferroelectric phase

Hrvoje Meštrić, Rüdiger-A. Eichel, K.-P. Dinse, Andrew Ozarowski, Johan van Tol, and Louis Claude Brunel

J. Appl. Phys. 96, 7440 (2004); http://dx.doi.org/10.1063/1.1808477 (5 pages) | Cited 27 times

Online Publication Date: 2 December 2004

Full Text: Read Online (HTML) | Download PDF

Show Abstract
The intrinsic iron(III) impurity center in polycrystalline lead titanate was investigated by means of high-frequency electron paramagnetic resonance spectroscopy in order to determine the local-environment sensitive fine-structure parameter D. At a spectrometer frequency of 190 GHz, a spectral analysis of a powder sample was unambiguously possible. The observed mean value D=+35.28 GHz can be rationalized if Fe3+ ions substitute for Ti4+ at the B site of the perovskite ABO3 lattice forming a directly coordinated FeTi′–VO⋅⋅ defect associate. A consistent fit of the multifrequency data necessitated the use of a distribution of the D values with a variance of about 1 GHz. This statistical distribution of values is probably related to more distant defects and vacancies.
Show PACS
77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
76.30.Fc Iron group (3d) ions and impurities (Ti-Cu)
71.55.Ht Other nonmetals
61.72.J- Point defects and defect clusters
77.80.-e Ferroelectricity and antiferroelectricity
Page 3 of 6 Pages Previous Page Next Page | Jump to Page
Close

Google Calendar

ADVERTISEMENT

Go to AIP Home   © AIP Publishing LLC
close