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28 Dec 1998

Volume 73, Issue 26, pp. 3803-3961

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Ruthenium: A superior compensator of InP

A. Dadgar, O. Stenzel, A. Näser, M. Zafar Iqbal, D. Bimberg, and H. Schumann

Appl. Phys. Lett. 73, 3878 (1998); http://dx.doi.org/10.1063/1.122898 (3 pages) | Cited 12 times

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The 4d-transition metal ruthenium presents a new dopant to fabricate thermally stable semi-insulating InP layers for both electron and hole injection. The layers are grown by low-pressure metalorganic chemical vapor deposition using tertiarybutylphosphine and trimethylindium as source materials for InP growth. Using bis(η5-2,4-dimethyl-pentadienyl)ruthenium(II) as precursor Ru doping concentrations of the order of 4×1018 cm−3 are achieved, determined by means of secondary ion mass spectroscopy. The Ru diffusion coefficient in InP is determined to DRu(800 °C) ⩽ 1×10−15 cm2/s which is four orders of magnitude smaller than for Fe. Resistivities obtained under electron and hole injection are above 6×107 Ω cm and 5×108 Ω cm, respectively. In deep level transient spectroscopy measurements under electron emission and hole emission, one deep level each with concentrations around 1016 cm−3, is observed. © 1998 American Institute of Physics.
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81.05.Ea III-V semiconductors
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
73.20.Hb Impurity and defect levels; energy states of adsorbed species
71.55.Eq III-V semiconductors

Quantum confinement effect in self-assembled, nanometer silicon dots

S. A. Ding, M. Ikeda, M. Fukuda, S. Miyazaki, and M. Hirose

Appl. Phys. Lett. 73, 3881 (1998); http://dx.doi.org/10.1063/1.122923 (3 pages) | Cited 24 times

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The first subband energy at the valence band of self-assembled silicon quantum dots grown by low-pressure chemical vapor deposition on ultrathin SiO2/Si substrates has been measured as an energy shift at the top of the valence band density of states by using high-resolution x-ray photoelectron spectroscopy. The systematic shift of the valence band maximum towards higher binding energy with decreasing the dot size is shown to be consistent with theoretical prediction. The charging effects of the silicon dots and the SiO2 layer by photoelectron emission during the measurements have been taken into account in determining the valence-band-edge energy. © 1998 American Institute of Physics.
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73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
73.20.At Surface states, band structure, electron density of states
79.60.Bm Clean metal, semiconductor, and insulator surfaces

Intrinsic charge transport properties of an organic single crystal determined using a multiterminal thin-film transistor

W. A. Schoonveld, J. Vrijmoeth, and T. M. Klapwijk

Appl. Phys. Lett. 73, 3884 (1998); http://dx.doi.org/10.1063/1.122924 (3 pages) | Cited 21 times

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We present an experimental approach to determine the intrinsic field-effect mobility in an organic single crystal as a function of the in-plane crystal-axis direction. Using a multiterminal geometry the experiment also excludes the effects of the contact resistances on the transport properties. We have applied the method to quaterthiophene thin films. At gate voltages above the threshold voltage, the channel conductance varies linearly with the applied gate voltage. The resulting charge carrier mobility is 1.2×10−3 cm2/V s. This value is constant over a period of weeks of continuous operation and does not vary from sample to sample, in contrast to the typically observed lower mobilities of polycrystalline quaterthiophene thin-film transistor devices. These results emphasize the need for well-characterized model systems to study the intrinsic transport properties of organic materials. © 1998 American Institute of Physics.
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72.80.Le Polymers; organic compounds (including organic semiconductors)
73.50.Dn Low-field transport and mobility; piezoresistance
85.30.Tv Field effect devices
73.61.Ph Polymers; organic compounds
85.65.+h Molecular electronic devices
72.20.Fr Low-field transport and mobility; piezoresistance

Measurement of gain current relations for InGaN multiple quantum wells

A. C. Abare, M. P. Mack, M. Hansen, J. S. Speck, L. A. Coldren, S. P. DenBaars, G. A. Meyer, S. L. Lehew, and G. A. Cooper

Appl. Phys. Lett. 73, 3887 (1998); http://dx.doi.org/10.1063/1.122925 (3 pages) | Cited 6 times

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Pulsed operation of in-plane laser diodes with InGaN multiple quantum well active regions was achieved. For uncoated chemically assisted ion beam etched facets, we obtained threshold current densities as low as 10.6 kA/cm2. The external differential quantum efficiency dependence on bar length was used to determine the internal optical loss and internal quantum efficiency of these devices and to calculate the modal gain in the device as a function of the terminal current density. Values of facet reflection were determined by a self-consistent analysis. We have measured 90 cm−1 of modal gain and estimate material gain exceeding 900 cm−1, at 20 kA/cm2. © 1998 American Institute of Physics.
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42.55.Px Semiconductor lasers; laser diodes
42.60.Da Resonators, cavities, amplifiers, arrays, and rings

Andreev reflection in Si-engineered Al/InGaAs hybrid junctions

Silvano De Franceschi, Francesco Giazotto, Fabio Beltram, Lucia Sorba, Marco Lazzarino, and Alfonso Franciosi

Appl. Phys. Lett. 73, 3890 (1998); http://dx.doi.org/10.1063/1.122926 (3 pages) | Cited 15 times

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Andreev-reflection dominated transport is demonstrated in Al/n-In0.38Ga0.62As superconductor–semiconductor junctions grown by molecular beam epitaxy on GaAs(001). High junction transparency was achieved in low-doped devices by exploiting Si interface bilayers to suppress the native Schottky barrier. It is argued that this technique is ideally suited for the fabrication of ballistic transport hybrid microstructures. © 1998 American Institute of Physics.
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73.61.Ey III-V semiconductors
73.40.Ns Metal-nonmetal contacts
74.50.+r Tunneling phenomena; Josephson effects

Effect of temperature on Ga2O3(Gd2O3)/GaN metal–oxide–semiconductor field-effect transistors

F. Ren, M. Hong, S. N. G. Chu, M. A. Marcus, M. J. Schurman, A. Baca, S. J. Pearton, and C. R. Abernathy

Appl. Phys. Lett. 73, 3893 (1998); http://dx.doi.org/10.1063/1.122927 (3 pages) | Cited 102 times

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Ga2O3(Gd2O3) was deposited on GaN for use as a gate dielectric in order to fabricate a depletion metal–oxide–semiconductor field-effect transistor (MOSFET). Analysis of the effect of temperature on the device shows that gate leakage is significantly reduced at elevated temperature relative to a conventional metal–semiconductor field-effect transistor fabricated on the same GaN layer. MOSFET device operation in fact improved upon heating to 400 °C. Modeling of the effect of temperature on contact resistance suggests that the improvement is due to a reduction in the parasitic resistances present in the device. © 1998 American Institute of Physics.
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85.30.Tv Field effect devices
85.30.De Semiconductor-device characterization, design, and modeling
73.40.Cg Contact resistance, contact potential
77.22.Jp Dielectric breakdown and space-charge effects

Dissociation of the 1.014 eV photoluminescence copper center in silicon crystal

M. Nakamura

Appl. Phys. Lett. 73, 3896 (1998); http://dx.doi.org/10.1063/1.122928 (3 pages) | Cited 7 times

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In order to determine dissociation energy of the 1.014 eV photoluminescence (PL) Cu center in silicon crystal, decay of the PL intensity of the center by annealing samples at various temperatures was measured. The samples were prepared by contamination of Cu from Cu solution and heat treatment at 700 °C followed by rapid cooling to room temperature. From the temperature dependence of the time constant of the decay of the PL center, activation energy of dissociation of the center was obtained. The value was 0.47+±0.05 eV, which was much smaller than that (1.02 eV) obtained by the decay of the deep level transient spectroscopy Cu center peak at Ev+0.09 eV. The present value could reasonably explain the rapid thermalization of rearrangement of the centers after the release of stress which had been observed earlier. © 1998 American Institute of Physics.
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71.55.Cn Elemental semiconductors
78.55.Ap Elemental semiconductors

Investigation of oval defects in InGaAs/GaAs strained-layer heterostructures using cathodoluminescence and wavelength dispersive spectroscopy

J. J. Russell-Harriott, J. Zou, A. R. Moon, D. J. H. Cockayne, and B. F. Usher

Appl. Phys. Lett. 73, 3899 (1998); http://dx.doi.org/10.1063/1.122929 (3 pages) | Cited 3 times

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Oval defects in In0.04Ga0.96As/GaAs strained-layer heterostructures have been investigated using cathodoluminescence (CL) and wavelength dispersive x-ray spectroscopy (WDS). WDS studies showed that the particulates seen at the center of oval defects are indium rich and gallium depleted. A luminescent halo was seen around the indium rich particulates in the CL mode. When the halo was studied further, it was shown that the peak obtained from CL spectroscopy due to the luminescent halo shifts to lower wavelengths as the beam is moved from the center of the oval defect to the edge of the halo region, indicating a decreasing gradient in indium concentration. © 1998 American Institute of Physics.
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68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
78.66.Fd III-V semiconductors
78.60.Hk Cathodoluminescence, ionoluminescence

SiO2-enhanced synthesis of Si nanowires by laser ablation

N. Wang, Y. F. Zhang, Y. H. Tang, C. S. Lee, and S. T. Lee

Appl. Phys. Lett. 73, 3902 (1998); http://dx.doi.org/10.1063/1.122930 (3 pages) | Cited 103 times

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Si nanowires with uniform size have been synthesized by laser ablation of highly pure Si powder targets mixed with SiO2. A bulk quantity of Si nanowires was successfully obtained by mixing 30%–70% of SiO2 into the Si powder target. SiO2 played a crucial role in enhancing the formation and growth of the Si nanowires. The morphology and microstructure of the Si nanowire tips have been systematically characterized by means of high-resolution transmission electron microscopy. No evidence of metal was found at the tips. The results suggest that Si oxide is more important than metal in catalyzing the formation of Si nanowires. © 1998 American Institute of Physics.
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81.07.-b Nanoscale materials and structures: fabrication and characterization
81.05.Cy Elemental semiconductors
81.15.Fg Pulsed laser ablation deposition
61.46.-w Structure of nanoscale materials
61.72.Mm Grain and twin boundaries
81.20.Ev Powder processing: powder metallurgy, compaction, sintering, mechanical alloying, and granulation
61.72.Nn Stacking faults and other planar or extended defects

Quantum wells due to ordering in GaInP

Y. Hsu, G. B. Stringfellow, C. E. Inglefield, M. C. DeLong, P. C. Taylor, J. H. Cho, and T.-Y. Seong

Appl. Phys. Lett. 73, 3905 (1998); http://dx.doi.org/10.1063/1.122931 (3 pages) | Cited 9 times

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CuPt ordering results in a reduction of the band-gap energy of GaInP. Thus, heterostructures and quantum wells can be produced by simply varying the order parameter, without changing the solid composition. Changes in the order parameter can be induced by changes in growth conditions. The disordered/ordered/disordered quantum wells described here are grown by changing the PH3 flow rate. Transmission electron microscopy results show that the quantum wells produced in this way are clearly defined, with abrupt interfaces. Low-temperature photoluminescence spectra show distinct peaks from quantum wells (QWs) of different widths. The QW photoluminescence peak energy increases with decreasing well width due to quantum size effects. The difference in band-gap energy between the ordered and disordered single layers is determined from photoluminescence excitation spectroscopy to be 0.06 eV. © 1998 American Institute of Physics.
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68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
78.55.Cr III-V semiconductors
78.66.Fd III-V semiconductors
81.05.Ea III-V semiconductors
81.15.Kk Vapor phase epitaxy; growth from vapor phase

Direct spectroscopic measurement of mounting-induced strain in high-power optoelectronic devices

J. W. Tomm, R. Müller, A. Bärwolff, T. Elsaesser, D. Lorenzen, F. X. Daiminger, A. Gerhardt, and J. Donecker

Appl. Phys. Lett. 73, 3908 (1998); http://dx.doi.org/10.1063/1.122932 (3 pages) | Cited 21 times

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Thermally induced strain caused by device packaging is studied in high-power semiconductor lasers by a noninvasive technique. Fourier-transform photocurrent measurements with intentionally strained laser array devices for 808 nm emission reveal spectral shifts of quantum-confined optical transitions in the optical active region. These shifts by up to 7 meV serve as a measure for strain and are compared with model calculations. For a given packaging architecture, about one quarter of the mounting-induced strain is transferred to the quantum-well region of the device. Spatially resolved measurements demonstrate a lateral strain gradient in the devices. © 1998 American Institute of Physics.
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42.55.Px Semiconductor lasers; laser diodes
42.60.Da Resonators, cavities, amplifiers, arrays, and rings
07.10.Pz Instruments for strain, force, and torque
73.50.Pz Photoconduction and photovoltaic effects

Temperature-dependent recombination in polymer composite light-emitting diodes

L. Bozano, S. E. Tuttle, S. A. Carter, and P. J. Brock

Appl. Phys. Lett. 73, 3911 (1998); http://dx.doi.org/10.1063/1.122933 (3 pages) | Cited 21 times

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We study the temperature dependence of the current–voltage and radiance–voltage curves in double-carrier injected polymer light-emitting devices comprised of poly(2-methoxy,5-(2′-ethyl-hexoxy)–p-phenylene vinylene) (MEH–PPV) and MEH–PPV/SiO2 as the active layer. The quantum efficiency increases significantly as the temperature is decreased in agreement with an increase in the recombination efficiency with decreasing temperature. Moreover, the bimolecular recombination efficiency saturates at low temperatures and high currents to a very high value for both the composite and plain MEH–PPV devices with the nanoparticles serving as charge traps only at moderately low current densities. Finally, we find that the order of magnitude improvement in radiance observed in some polymer/nanoparticle composites is due to an increase in the effective electric field across the device. © 1998 American Institute of Physics.
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85.60.Jb Light-emitting devices
73.50.Gr Charge carriers: generation, recombination, lifetime, trapping, mean free paths
73.61.Ph Polymers; organic compounds

Electrical characterization of electroluminescent polymer/nanoparticle composite devices

P. W. M. Blom, H. F. M. Schoo, and M. Matters

Appl. Phys. Lett. 73, 3914 (1998); http://dx.doi.org/10.1063/1.122934 (3 pages) | Cited 25 times

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The current–voltage characteristics of light-emitting devices containing thin films of poly(dialkoxy-p-phenylene vinylene) (PPV) incorporated with silicon dioxide nanoparticles have been investigated. It is demonstrated that the current enhancement of the devices containing composite layers can be modeled by assuming that the effective thickness of the composite layers is about half of their actual thickness. Field-effect measurements reveal that the mobility of the charge carriers in PPV is not significantly changed by the incorporation of nanoparticles. © 1998 American Institute of Physics.
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85.60.Jb Light-emitting devices
73.61.Ph Polymers; organic compounds

Internal photoemission measurement of Schottky barrier height for Ni on AlGaN/GaN heterostructure

L. S. Yu, Q. J. Xing, D. Qiao, S. S. Lau, K. S. Boutros, and J. M. Redwing

Appl. Phys. Lett. 73, 3917 (1998); http://dx.doi.org/10.1063/1.122935 (3 pages) | Cited 21 times

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The internal photoemission method was used to measure the Schottky barrier height of Ni on AlGaN/GaN heterostructures. A barrier height of 1.31 eV was found for the Ni/Al0.15Ga0.85N/GaN heterojunction structure, as compared to a barrier height of 1.28 and 1.02 eV for the Ni/Al0.15Ga0.85N and Ni/GaN Schottky diodes, respectively. © 1998 American Institute of Physics.
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85.30.Hi Surface barrier, boundary, and point contact devices
73.30.+y Surface double layers, Schottky barriers, and work functions
73.40.Ns Metal-nonmetal contacts
85.30.Kk Junction diodes

Correlation between barrier height and band offsets in metal/Si1−xGex/Si heterostructures

O. Nur, M. Karlsteen, M. Willander, R. Turan, B. Aslan, M. O. Tanner, and K. L. Wang

Appl. Phys. Lett. 73, 3920 (1998); http://dx.doi.org/10.1063/1.122936 (3 pages) | Cited 7 times

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The variation of barrier height with the band gap in the metal/heterojunction systems is related to how the Fermi level position varies with respect to band edges. If the Fermi level is pinned by the interface states its movement will also correspond to the movement of the neutrality level at the interface. Metal/Si1−xGex/Si heterostructures (0 ⩽ x ⩽ 0.24) for both n- and p-type substrates were studied to understand the relation between Schottky barrier, Fermi level movement, and the band gap variations. It was shown that a correlation exists between Schottky barrier height variation and band-offset values ΔEc and ΔEv. For n-type substrate, measured barrier height differences are almost the same as the band offsets in the conduction band ΔEc. For p-type substrates they were found to be slightly smaller than ΔEv. This shows that Fermi level position relative to the conduction band edge does not change with band gap variation. © 1998 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

HF-chemical etching of the oxide layer near a SiO2/Si(111) interface

Noriyuki Miyata, Heiji Watanabe, and Masakazu Ichikawa

Appl. Phys. Lett. 73, 3923 (1998); http://dx.doi.org/10.1063/1.122937 (3 pages) | Cited 5 times

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The HF-chemical etching process near the SiO2/Si(111) interface (<1 nm) is investigated by scanning reflection electron microscopy and microprobe Auger electron spectroscopy. The HF etching of the SiO2 layer thermally grown on an atomically flat Si(111)-7×7 surface progresses in a layer-by-layer manner, and then the final layer of oxide ( ∼ 0.3 nm) is removed in a two-dimensional void expansion with the H-terminated Si surface. This very uniform HF etching is thought to reflect the structural anisotropy of the SiO2 layer formed near the SiO2/Si(111) interface. © 1998 American Institute of Physics.
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81.65.Cf Surface cleaning, etching, patterning
79.20.Fv Electron impact: Auger emission
68.35.Ct Interface structure and roughness
68.35.B- Structure of clean surfaces (and surface reconstruction)
68.35.Dv Composition, segregation; defects and impurities

Holographic nanopatterning of the organic semiconductor poly(p-phenylene vinylene)

G. Gigli, R. Rinaldi, C. Turco, P. Visconti, R. Cingolani, and F. Cacialli

Appl. Phys. Lett. 73, 3926 (1998); http://dx.doi.org/10.1063/1.122938 (3 pages) | Cited 15 times

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We report a flexible method for the patterning of organic semiconductors in the submicrometer range, which we have successfully applied to thin films of poly(p-phenylene vinylene) (PPV) prepared on a variety of substrates, such as quartz, indium–tin oxide coated glass, or inorganic dielectric mirrors. The method is based on holographic lithography performed by a corner cube interferometer of our own design and construction, followed by Ar-ion etching. © 1998 American Institute of Physics.
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81.05.Lg Polymers and plastics; rubber; synthetic and natural fibers; organometallic and organic materials
81.65.Cf Surface cleaning, etching, patterning
81.07.-b Nanoscale materials and structures: fabrication and characterization
81.16.-c Methods of micro- and nanofabrication and processing
85.35.-p Nanoelectronic devices
42.40.Kw Holographic interferometry; other holographic techniques
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
85.40.Hp Lithography, masks and pattern transfer
42.40.My Applications
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Performance of high-Tc superconducting quantum interference devices with resistively shunted inductances

D. J. Kang, W. E. Booij, M. G. Blamire, and E. J. Tarte

Appl. Phys. Lett. 73, 3929 (1998); http://dx.doi.org/10.1063/1.122939 (3 pages) | Cited 4 times

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The voltage modulation depths, ΔV of high-Tc direct current superconducting quantum interference devices (SQUIDs) with resistors connected in parallel with their inductances were investigated. Both the junctions and resistors in the SQUIDs were fabricated using focused electron-beam irradiation. The effect of varying the resistor value (using focused ion-beam trimming) and the screening parameter βL (by varying the temperature and hence the junction critical current) were studied. Significant enhancement of ΔV relative to an equivalent unshunted SQUID for βL values up to 50 was observed, and the most effective shunt resistor value was found to be approximately equal to the junction resistance. © 1998 American Institute of Physics.
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85.25.Dq Superconducting quantum interference devices (SQUIDs)
74.72.-h Cuprate superconductors

Direct current voltage increment due to ac coupling in a high Tc superconducting coil

N. Shaked, I. A. Al-Omari, A. Friedman, Y. Wolfus, M. Sinvani, A. Shaulov, and Y. Yeshurun

Appl. Phys. Lett. 73, 3932 (1998); http://dx.doi.org/10.1063/1.122940 (3 pages) | Cited 3 times

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The voltage–current characteristics of a superconducting coil, made of multifilamentary silver-sheathed Bi2Sr2Ca2Cu3O10+δ tape, are investigated. We find that a small ac current Iac superimposed on a relatively large dc current Idc causes a significant increase in the coil dc voltage, approximately proportional to Idc, Iac2, and the ac frequency. We attribute this effect to the nonlinear magnetoresistance of the coil, and discuss its significance in power applications of high Tc superconducting coils, such as fault current limiters and superconducting magnetic energy storage devices. © 1998 American Institute of Physics.
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74.72.-h Cuprate superconductors
74.25.F- Transport properties
74.25.Sv Critical currents
74.25.Uv Vortex phases (includes vortex lattices, vortex liquids, and vortex glasses)
84.60.Ve Energy storage systems, including capacitor banks

Enhancement of transport critical current densities in Bi2Sr2Ca2Cu3Ox tapes by fission tracks

G. W. Schulz, C. Klein, H. W. Weber, S. Moss, R. Zeng, S. X. Dou, R. Sawh, Y. Ren, and R. Weinstein

Appl. Phys. Lett. 73, 3935 (1998); http://dx.doi.org/10.1063/1.122941 (3 pages) | Cited 14 times

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Bi2Sr2Ca2Cu3Ox (Bi-2223) tapes were processed by the standard powder-in-tube technique, but small amounts of UO4 were added prior to processing. Both U-doped and undoped tapes were subsequently exposed to a reactor spectrum of neutrons. Whereas the undoped materials show moderate enhancements of the critical current densities Jc due to the pinning action of the fast-neutron-induced collision cascades, Jc in the U-doped tapes increases by factors of 10–20 due to thermal-neutron-induced fission of 235U and the subsequent formation of fission tracks. Since the enhancements are particularly pronounced, when the magnetic field is applied perpendicular to the tape surface, the characteristic Jc anisotropy is strongly reduced in a certain field range. At the same time, the irreversibility field at 77 K is doubled for both field orientations. © 1998 American Institute of Physics.
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74.72.-h Cuprate superconductors
74.25.Sv Critical currents
74.25.Uv Vortex phases (includes vortex lattices, vortex liquids, and vortex glasses)
74.62.Dh Effects of crystal defects, doping and substitution

Ultimate quantum efficiency of a superconducting hot-electron photodetector

K. S. Il’in, I. I. Milostnaya, A. A. Verevkin, G. N. Gol’tsman, E. M. Gershenzon, and Roman Sobolewski

Appl. Phys. Lett. 73, 3938 (1998); http://dx.doi.org/10.1063/1.122942 (3 pages) | Cited 23 times

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The quantum efficiency and current and voltage responsivities of fast hot-electron photodetectors, fabricated from superconducting NbN thin films and biased in the resistive state, have been shown to reach values of 340, 220 A/W, and 4×104 V/W, respectively, for infrared radiation with a wavelength of 0.79 μm. The characteristics of the photodetectors are presented within the general model, based on relaxation processes in the nonequilibrium electron heating of a superconducting thin film. The observed, very high efficiency and sensitivity of the superconductor absorbing the photon are explained by the high multiplication rate of quasiparticles during the avalanche breaking of Cooper pairs. © 1998 American Institute of Physics.
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85.25.Pb Superconducting infrared, submillimeter and millimeter wave detectors
74.78.-w Superconducting films and low-dimensional structures
74.70.Ad Metals; alloys and binary compounds (including A15, MgB2, etc.)
74.25.N- Response to electromagnetic fields
74.25.Kc Phonons

Growth of highly oriented Pb(Zr, Ti)O3 films on MgO-buffered oxidized Si substrates and its application to ferroelectric nonvolatile memory field-effect transistors

Nasir Abdul Basit, Hong Koo Kim, and Jean Blachere

Appl. Phys. Lett. 73, 3941 (1998); http://dx.doi.org/10.1063/1.122943 (3 pages) | Cited 27 times

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We have grown highly oriented lead zirconate titanate [Pb(Zr, Ti)O3 or PZT] films on oxidized silicon substrates using a thin MgO buffer layer (7–70 nm thick). Ferroelectric nonvolatile memory field-effect transistors (FETs) were successfully fabricated using the metal/PZT/MgO/SiO2/Si structure in conjunction with radio-frequency sputter deposition of PZT and MgO films. The fabricated devices show excellent performance in ferroelectric polarization switching and memory retention. The results indicate that a thin MgO buffer serves well not only as a template layer for the growth of oriented PZT films on amorphous substrates, but also as a diffusion barrier between a ferroelectric and a substrate during device fabrication, protecting the SiO2/Si interface and the FET channel region. © 1998 American Institute of Physics.
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77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
77.80.Fm Switching phenomena
85.50.-n Dielectric, ferroelectric, and piezoelectric devices
81.15.Cd Deposition by sputtering
77.55.-g Dielectric thin films
85.30.Tv Field effect devices
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Engineering of the magnetic properties of strained quantum dots

Jacob B. Khurgin, F. Jin, and A. Obeidat

Appl. Phys. Lett. 73, 3944 (1998); http://dx.doi.org/10.1063/1.122944 (3 pages) | Cited 2 times

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Exchange interactions between the holes confined in arrays of strained quantum dots subject to compressive and tensile strain are shown to lead to ferrimagnetic arrangement of magnetic moments. Using example of strained In1−xGaxAs quantum dots on InP substrate, it is shown how magnetic properties of a semiconductor material can be engineered without resorting to doping with magnetic ions, and the Curie temperature is estimated to be of the order of 25 K. Potential applications in information storage and processing are considered. © 1998 American Institute of Physics.
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75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
75.50.Pp Magnetic semiconductors
75.50.Gg Ferrimagnetics
75.80.+q Magnetomechanical effects, magnetostriction
75.30.Et Exchange and superexchange interactions
75.30.Kz Magnetic phase boundaries (including classical and quantum magnetic transitions, metamagnetism, etc.)
75.10.Lp Band and itinerant models
75.30.Cr Saturation moments and magnetic susceptibilities

Probing submicron nanomagnets by magneto-optics

R. P. Cowburn, D. K. Koltsov, A. O. Adeyeye, and M. E. Welland

Appl. Phys. Lett. 73, 3947 (1998); http://dx.doi.org/10.1063/1.122945 (3 pages) | Cited 53 times

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A hybrid magneto-optical magnetometer and optical microscope has been designed and constructed for probing the magnetic properties of submicron nanomagnets. 10-nm-thick square nanomagnets have been fabricated individually and in small arrays from Ni80Fe14Mo5 (“supermalloy”) by electron-beam lithography. Hysteresis loops with a good signal-to-noise ratio have been obtained from individual nanomagnets as small as 400 nm and from (5 μm)2 arrays of nanomagnets ranging in size from 500 to 75 nm. © 1998 American Institute of Physics.
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75.50.Kj Amorphous and quasicrystalline magnetic materials
78.20.Ls Magneto-optical effects
07.55.Jg Magnetometers for susceptibility, magnetic moment, and magnetization measurements
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
75.50.Bb Fe and its alloys
07.60.Pb Conventional optical microscopes
78.66.Bz Metals and metallic alloys

Electronic transport properties of (001)/(110) oriented La2/3MnO3−δ thin films

Chun-Che Chen and Alex de Lozanne

Appl. Phys. Lett. 73, 3950 (1998); http://dx.doi.org/10.1063/1.122946 (3 pages) | Cited 10 times

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We report the unusual transport properties found in La2/3MnO3−δ thin films on Al2O3 (1math02). Powder x-ray diffraction shows that the film has a mixture of perpendicular (110) and (001) crystal orientations. Unlike epitaxial or polycrystalline La1−xMnO3−δ samples, in which the peak resistance temperature Tp shifts toward a higher temperature under the influence of magnetic field, the Tp of this particular film remains almost the same even in fields up to 5 T. The film becomes insulating at a low temperature Tm( ∼ 45 K), but the trend is reversed by the applied magnetic field. © 1998 American Institute of Physics.
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73.61.At Metal and metallic alloys
68.55.-a Thin film structure and morphology
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