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3 Jul 1995

Volume 67, Issue 1, pp. 1-146

Page 2 of 2 Pages Previous Page | Jump to Page

Instability mechanisms for the hydrogenated amorphous silicon thin‐film transistors with negative and positive bias stresses on the gate electrodes

Ya‐Hsiang Tai, Jun‐Wei Tsai, Huang‐Chung Cheng, and Feng‐Cheng Su

Appl. Phys. Lett. 67, 76 (1995); http://dx.doi.org/10.1063/1.115512 (3 pages) | Cited 6 times

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The hydrogenated amorphous silicon (a‐Si:H) thin film transistors (TFTs) with silicon nitride as a gate insulator have been stressed with negative and positive bias to realize the instability mechanisms. It is found that the threshold voltages of the a‐Si:H TFTs are positively shifted under low negative bias stress and then negatively shifted for large negative gate bias. The positive threshold voltage shift is ascribed to the increased states in the band gap near the conduction band by the negative gate bias. As the negative bias continuously increases, the hole trapping in the silicon nitride or at the a‐Si:H/silicon nitride interface will become dominant, resulting in the negative threshold voltage shift. A similar turnaround phenomenon is also observed with respect to the stress time. On the other hand, for the TFTs stressed with positive gate bias, the monotonic increase of the threshold voltage shift with stress time is attributed to the state creation. Nevertheless, the distributions of the created states in the energy band gap for the a‐SiH TFTs after the stress will be affected by the bias polarity based on the defect pool model, reflecting the asymmetrical subthreshold swing change against the positive and negative stress bias. © 1995 American Institute of Physics.
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85.30.Hi Surface barrier, boundary, and point contact devices
73.61.Jc Amorphous semiconductors; glasses
73.20.At Surface states, band structure, electron density of states
73.50.Dn Low-field transport and mobility; piezoresistance

Subpicosecond electrical pulse generation by edge illumination of silicon and indium phosphide photoconductive switches

Chia‐Chi Wang, Marc Currie, Roman Sobolewski, and Thomas Y. Hsiang

Appl. Phys. Lett. 67, 79 (1995); http://dx.doi.org/10.1063/1.115513 (3 pages) | Cited 14 times

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Using a femtosecond pulsed laser, ultrafast electrical pulses were optoelectronically generated on silicon and indium phosphide by edge illumination of a coplanar transmission line. Backing up theory with experiment, we demonstrate that this pulse‐generation method is material independent, thus providing a powerful tool for broadband characterization of devices made on a wide range of semiconductor substrates. We also demonstrate that edge illumination enables the generation of 550 fs electrical pulses on indium phosphide and 800 fs pulses on silicon—the fastest pulses to date on bulk silicon. © 1995 American Institute of Physics.
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84.30.Ng Oscillators, pulse generators, and function generators
85.60.-q Optoelectronic devices
85.30.Hi Surface barrier, boundary, and point contact devices

Band‐tail photoluminescence in polycrystalline silicon thin films

A. U. Savchouk, S. Ostapenko, G. Nowak, J. Lagowski, and L. Jastrzebski

Appl. Phys. Lett. 67, 82 (1995); http://dx.doi.org/10.1063/1.115515 (3 pages) | Cited 25 times

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We have found a new photoluminescence (PL) band with a maximum at 0.9 eV and a halfwidth of 0.1 eV at 4.2 K in polycrystalline Si thin films deposited on glass at 625 °C. The PL band strongly shifts toward low energy with increasing the temperature (1.3 meV/K) and toward high energy with increasing the excitation intensity. Hydrogenation of polycrystalline Si enhances the PL intensity by factor of 3 to 5. The luminescence characteristics are consistent with radiative recombination of electrons and holes trapped in tail states of the conduction and the valence band, respectively. Excellent agreement is achieved between the 0.9 eV band shape and theoretical calculations based on a band‐tail recombination. It is also argued that a corresponding luminescence spectroscopy provides a new possibility for band‐tail diagnostics in polycrystalline Si thin films. © 1995 American Institute of Physics.
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78.66.Db Elemental semiconductors and insulators
78.55.Hx Other solid inorganic materials
73.61.Cw Elemental semiconductors

Kinetics of Si1−xGex/Si(0≤x≤1) growth by molecular beam epitaxy using disilane and germanium

F. C. Zhang, J. Singh, and P. K. Bhattacharya

Appl. Phys. Lett. 67, 85 (1995); http://dx.doi.org/10.1063/1.115516 (3 pages)

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Molecular beam epitaxy of Si1−xGex alloys, using gaseous Si2H6 and solid Ge as sources, has been studied over the entire composition range (0≤x≤1). From the measured growth rates as a function of x, it is clear that the presence of Ge tends to decrease the Si incorporation rate. This establishes growth via adatom migration to kink sites in a dissociative chemisorption process. © 1995 American Institute of Physics.
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81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy

Efficient lateral minority carrier transport in proton‐implanted p‐type silicon

D. C. Leung, P. R. Nelson, O. M. Stafsudd, J. B. Parkinson, and G. E. Davis

Appl. Phys. Lett. 67, 88 (1995); http://dx.doi.org/10.1063/1.115517 (3 pages) | Cited 2 times

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A highly efficient lateral transport mechanism has been observed in stable defect layers (SDL) in p‐type silicon. The SDLs were produced by proton implantation followed by rapid thermal anneal. Photogenerated carriers have been collected at a Schottky junction several millimeters away from the generation site. This transport distance is more than 30 times the diffusion length in comparable bulk material. A model is proposed in which bending of the energy bands near the SDL expels majority carriers, leaving no substantial recombination mechanism for minority carriers trapped in the layer. © 1995 American Institute of Physics.
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72.40.+w Photoconduction and photovoltaic effects
61.72.uf Ge and Si
85.60.Dw Photodiodes; phototransistors; photoresistors
84.60.Jt Photoelectric conversion

Three‐photon photoemission from GaAs–O–Cs negative electron affinity surfaces induced by 2.06 μm nanosecond laser pulses

Liming Wang, Zhao Cheng, Qi Ping, and Xun Hou

Appl. Phys. Lett. 67, 91 (1995); http://dx.doi.org/10.1063/1.115518 (3 pages) | Cited 2 times

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Three‐photon photoemission effect on GaAs–O–Cs negative electron affinity surfaces (NEA) was studied by using a nanosecond pulsed laser at 2.06 μm wavelength. The photocurrent densities from the photocathodes with different sensitivities were measured as a function of laser intensity at both room and liquid nitrogen temperatures (77 K). The dependence of photocurrent density on the light intensity shows a typical slope of three in logarithmic plot. The results are interpreted in terms of multiphoton photoemission (MPPE) effect. The influence of thermal electron emission to MPPE are discussed. © 1995 American Institute of Physics.
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79.60.Bm Clean metal, semiconductor, and insulator surfaces
79.20.Ds Laser-beam impact phenomena
73.20.At Surface states, band structure, electron density of states

Growth of device quality GaN at 550 °C by atomic layer epitaxy

N. H. Karam, T. Parodos, P. Colter, D. McNulty, W. Rowland, J. Schetzina, N. El‐Masry, and Salah M. Bedair

Appl. Phys. Lett. 67, 94 (1995); http://dx.doi.org/10.1063/1.115519 (3 pages) | Cited 28 times

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GaN single crystal films were grown by atomic layer epitaxy at 550 °C. The room temperature photoluminescence properties of these low‐temperature‐grown films are dominated by band edge emission with intensity comparable to those grown by metalorganic chemical vapor deposition at 1000 °C. The as‐grown films have background‐carrier concentrations that can be controlled to levels in the 1016/cm−3 range. Atomic layer epitaxy is therefore a good approach to the low temperature growth of nitride compounds. © 1995 American Institute of Physics.
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81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
78.55.Cr III-V semiconductors
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)

Ordering phenomena in InAs strained layer morphological transformation on GaAs (100) surface

G. E. Cirlin, G. M. Guryanov, A. O. Golubok, S. Ya. Tipissev, N. N. Ledentsov, P. S. Kop’ev, M. Grundmann, and D. Bimberg

Appl. Phys. Lett. 67, 97 (1995); http://dx.doi.org/10.1063/1.115520 (3 pages) | Cited 39 times

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Initial stage of InAs pseudomorphic layer transformation (1–3 ML) on GaAs (100) singular surface may result for sequential submonolayer molecular beam epitaxy in formation of a pseudoperiodic array of InAs ‘‘wires’’ along the [001] direction. Complex parquet structures having similar anisotropy are formed on misoriented surface (3° towards [0–11] direction). Increase in growth interruption time after each growth cycle for 2 ML InAs deposited on singular surface results in decomposition of the wires into dots arranged in a 2D square lattice. Intentional substrate misorientation stabilizes the initial ordering effect along [001] and does not change the direction of anisotropy. © 1995 American Institute of Physics.
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68.35.B- Structure of clean surfaces (and surface reconstruction)
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
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

Thermoelectric figure of merit of quantum wire superlattices

D. A. Broido and T. L. Reinecke

Appl. Phys. Lett. 67, 100 (1995); http://dx.doi.org/10.1063/1.115495 (3 pages) | Cited 35 times

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The electrical conductivity, the thermoelectric power, and the electrical contribution to the thermal conductivity of quantum wire superlattices have been studied. The effects of tunneling through the barriers due to finite potential off‐sets and of the thermal currents through the barrier layers are shown to be essential to describe properly the thermoelectric figure of merit of realistic quantum wire superlattices. The figure of merit exhibits a maximum as a function of superlattice period which, for large barrier off‐sets, is found to be substantially enhanced over that for the bulk material and also larger than that for quantum well superlattices. © 1995 American Institute of Physics.
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72.20.Pa Thermoelectric and thermomagnetic effects
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
73.50.Lw Thermoelectric effects

Temperature dependence of the photoluminescence of Zn1−xCdxSe/ZnSe strained‐layer quantum wells

E. Tournié, C. Morhain, M. Leroux, C. Ongaretto, and J. P. Faurie

Appl. Phys. Lett. 67, 103 (1995); http://dx.doi.org/10.1063/1.115496 (3 pages) | Cited 14 times

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We investigate by temperature‐dependent photoluminescence (PL) spectroscopy between 9 K and 300 K Zn1−xCdxSe/ZnSe strained‐layer quantum wells (QWs) with Cd contents ranging between 12% and 19% and QW thicknesses between 9 and 175 Å, i.e., with confinement energies up to 220 meV. In the whole temperature range the PL spectra are dominated by E1‐HH1 free‐exciton recombinations. Between 9 and 300 K the intensity of this line is reduced by three to four orders of magnitude while transitions involving excited states progressively emerge. An analysis of the thermal quenching of the PL intensity reveals that for all confinement energies the escape of excitons out of the QWs is the mechanism responsible for this quenching near 300 K. © 1995 American Institute of Physics.
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78.55.Et II-VI semiconductors
78.66.Hf II-VI semiconductors

InP/InGaAs photodetector based on a high electron mobility transistor layer structure: Its response at 1.3 μm wavelength

M. Horstmann, M. Marso, A. Fox, F. Rüders, M. Hollfelder, H. Hardtdegen, P. Kordos, and H. Lüth

Appl. Phys. Lett. 67, 106 (1995); http://dx.doi.org/10.1063/1.115497 (3 pages) | Cited 4 times

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We report on the investigation of the room‐temperature optoelectronic behavior of a metal–semiconductor–metal two‐dimensional electron gas photodiode based on the two‐dimensional electron gas of a high electron mobility transistor structure. The photodetector is fabricated in the InP/InGaAs material system, without use of Al‐containing layers. Optoelectronic measurements on a device with a finger spacing of 3 μm show a full width at half‐maximum (FWHM) of the pulse response of ≤60 ps, which is the resolution limit of our measurement equipment. Low‐temperature measurements at 40 K with electro‐optical sampling at a wavelength of 890 nm show a FWHM of 1 ps. © 1995 American Institute of Physics.
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85.60.Gz Photodetectors (including infrared and CCD detectors)
85.60.Dw Photodiodes; phototransistors; photoresistors
73.40.Sx Metal-semiconductor-metal structures
73.61.Ey III-V semiconductors

Ballistic transport in one‐dimensional constrictions formed in deep two‐dimensional electron gases

K. J. Thomas, M. Y. Simmons, J. T. Nicholls, D. R. Mace, M. Pepper, and D. A. Ritchie

Appl. Phys. Lett. 67, 109 (1995); http://dx.doi.org/10.1063/1.115498 (3 pages) | Cited 45 times

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We show that small structures can be defined in high mobility two‐dimensional electron gases formed at a depth of 2770 Å below the surface in GaAs/Al0.33Ga0.67As heterostructures. The differential conductance of one‐dimensional constrictions defined by split gates in such deep electron gases showed more than 20 quantised plateaus. The absence of resonant structures on the plateaus demonstrates the absence of potential fluctuations in the constrictions. By applying a dc source‐drain bias we have measured the energy spacings of the first 18 subbands, and the effect of a small perpendicular magnetic field on the energy spacings has been investigated. © 1995 American Institute of Physics.
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73.40.Kp III-V semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
73.50.-h Electronic transport phenomena in thin films

Electrical properties and microstructures of Au/Pt/Ti/Ni ohmic contacts to p‐type ZnTe

Kazuhiro Mochizuki, Akihisa Terano, Masayuki Momose, Akira Taike, Masahiko Kawata, Jun Gotoh, and Shin‐ichi Nakatsuka

Appl. Phys. Lett. 67, 112 (1995); http://dx.doi.org/10.1063/1.115500 (3 pages) | Cited 5 times

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Electrical properties and microstructures of Au/Pt/Ti/Ni ohmic contacts to p‐type ZnTe were investigated using the transmission line model method and cross‐sectional transmission electron microscopy. The specific contact resistance decreases when the annealing temperature is increased and reaches a minimum at 300 °C. The formation of NiTe2 from the reaction between Ni and ZnTe plays an important role in lowering the contact resistance. A contact stability test performed at 102 °C suggests that these ohmic contacts are stable even under high‐current injection. © 1995 American Institute of Physics.
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73.40.Cg Contact resistance, contact potential
73.61.Ga II-VI semiconductors
68.55.Nq Composition and phase identification
68.37.Hk Scanning electron microscopy (SEM) (including EBIC)
68.37.Lp Transmission electron microscopy (TEM)

AlGaN pn junctions

V. A. Dmitriev, K. Irvine, C. H. Carter, A. S. Zubrilov, and D. V. Tsvetkov

Appl. Phys. Lett. 67, 115 (1995); http://dx.doi.org/10.1063/1.115501 (3 pages) | Cited 13 times

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AlGaN pn homo‐ and heterojunctions were fabricated on silicon carbide substrates by metalorganic chemical vapor deposition. AlN concentration in AlGaN layers ranged from 2 to 8 mol %. Mesa structures were made by reactive ion etching. Electroluminescence (EL) from AlGaN pn junctions was studied. EL peaks associated with near band‐to‐band transition in AlGaN were detected. The minimum wavelength of EL peak of ∼348 nm (hν∼3.56 eV, 300 K) was measured for a p‐Al0.08GaN0.92/n‐Al0.06Ga0.94N heterojunction. The dependence of the photon energy of the edge EL peak on AlN concentration in AlGaN was measured. © 1995 American Institute of Physics.
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73.40.Kp III-V semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
81.15.Kk Vapor phase epitaxy; growth from vapor phase
78.60.Fi Electroluminescence
85.60.Jb Light-emitting devices

Mapping of subsurface inhomogeneities in semiconductors using differential reflectance microscopy

J. Tann and M. Gal

Appl. Phys. Lett. 67, 118 (1995); http://dx.doi.org/10.1063/1.115502 (3 pages) | Cited 1 time

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We have developed a sensitive optical technique that allows two‐dimensional mapping of subsurface inhomogeneities of semiconductors. Using this contactless, room temperature technique, which is based on differential reflectance spectroscopy, we have been able to generate relief maps which show the spatial distribution of damage/defects in a number of III–V compounds and Si. © 1995 American Institute of Physics.
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78.47.-p Spectroscopy of solid state dynamics
07.79.Fc Near-field scanning optical microscopes
61.72.Hh Indirect evidence of dislocations and other defects (resistivity, slip, creep, strains, internal friction, EPR, NMR, etc.)
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

C60 thin film transistors

R. C. Haddon, A. S. Perel, R. C. Morris, T. T. M. Palstra, A. F. Hebard, and R. M. Fleming

Appl. Phys. Lett. 67, 121 (1995); http://dx.doi.org/10.1063/1.115503 (3 pages) | Cited 259 times

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N‐channel field effect transistors with excellent device characteristics have been fabricated by utilizing C60 as the active element. Measurements on C60 thin films in ultrahigh vacuum show on‐off ratios as high as 106 and field effect mobilities up to 0.08 cm2/V s. © 1995 American Institute of Physics.
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85.30.Tv Field effect devices
73.50.Dn Low-field transport and mobility; piezoresistance
73.61.Ph Polymers; organic compounds

Lateral quantization effects in lithographically defined CdZnSe/ZnSe quantum dots and quantum wires

M. Illing, G. Bacher, T. Kümmell, A. Forchel, T. G. Andersson, D. Hommel, B. Jobst, and G. Landwehr

Appl. Phys. Lett. 67, 124 (1995); http://dx.doi.org/10.1063/1.115504 (3 pages) | Cited 44 times

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Quantum dots and quantum wires based on CdZnSe/ZnSe single quantum well heterostructures have been achieved using electron beam lithography and wet chemical etching. Photoluminescence spectra of the dot and wire structures show a blue shift due to lateral quantization for lateral dimensions below 40 nm. For the dot ground state, a lateral confinement energy of 16 meV is obtained for 28 nm diameter structures. For wires with widths on the order of 20 nm, lateral confinement energies of about 5 meV are observed. The dot diameter and wire width dependence of the emission energies can be described based on a square well potential and the measured sizes of the structures. © 1995 American Institute of Physics.
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73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
78.55.Et II-VI semiconductors
81.65.-b Surface treatments
85.40.Hp Lithography, masks and pattern transfer

Effect of dislocation reduction via strained InGaAs interlayers in GaAs grown on Si(001)

Yoko Uchida, Yoshiaki Yazawa, and Terunori Warabisako

Appl. Phys. Lett. 67, 127 (1995); http://dx.doi.org/10.1063/1.115505 (3 pages) | Cited 3 times

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The effects of strain and In content on dislocation reduction was studied by introducing an InGaAs strained layer into a GaAs layer on a Si substrate. The two effects were separated by using the strain energy that accumulates in the InGaAs layer, since the strain in an InGaAs layer varies with In content. The results show that the variation in dislocation density depends on the strain and not on the In content. A strain energy of 250 dyn/cm was sufficient for effectively reducing dislocations in both the InGaAs layer and in the GaAs overlayer. However, when the strain energy was over 500 dyn/cm, the number of dislocations increased when an InGaAs layer was introduced. © 1995 American Institute of Physics.
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68.60.Bs Mechanical and acoustical properties
61.72.Lk Linear defects: dislocations, disclinations

Enhancement of transport critical current densities at 75 K in (Bi,Pb)2Sr2Ca2Cu3Oy/Ag tapes by means of fission tracks from irradiation by 0.8 GeV protons

H. Safar, J. H. Cho, S. Fleshler, M. P. Maley, J. O. Willis, J. Y. Coulter, J. L. Ullmann, P. W. Lisowski, G. N. Riley, M. W. Rupich, J. R. Thompson, and L. Krusin‐Elbaum

Appl. Phys. Lett. 67, 130 (1995); http://dx.doi.org/10.1063/1.115506 (3 pages) | Cited 44 times

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The transport critical current density Jc of oxide‐powder‐in‐tube mono‐ and multifilamentary Bi‐2223/Ag tapes has been determined before and after irradiation by 0.8 GeV protons at fluences up to 7.0×1016 protons/cm2. Proton‐induced fission of the Bi nuclei produced up to 8.6×1013 fissions/cm3, creating long tracks at densities equivalent to matching fields up to 1.1 T. Relative to unirradiated tapes, Jc values at 75 and 64 K show no decrease in self field, indicating no breakdown of intergranular coupling, and show large, dose‐dependent enhancements in magnetic fields oriented parallel to the tape normal. © 1995 American Institute of Physics.
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74.78.-w Superconducting films and low-dimensional structures
74.25.Sv Critical currents
84.71.Mn Superconducting wires, fibers, and tapes
81.40.Rs Electrical and magnetic properties related to treatment conditions
FREE

Low 1/f normal‐state resistance noise in high‐resistivity YBa2Cu3Oy films

N. Y. Chen, R. Jonker, V. C. Matijasevic, H. M. Jaeger, and J. E. Mooij

Appl. Phys. Lett. 67, 133 (1995); http://dx.doi.org/10.1063/1.115507 (3 pages) | Cited 5 times

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We have measured 1/f resistance noise at room temperature in laser‐ablated YBa2Cu3Oy (YBCO) thin films over a wide range of normal‐state resistivities. Surprisingly, the high resistivity films exhibit lower normalized noise powers than the low resistivity films. The lowest normalized noise power is 100 times lower than any previously reported values for single crystals of YBCO and is comparable to the lowest noise levels found in other cuprates. Upon oxygen reduction, the noise power in the high resistivity films increases monotonically whereas it decreases in the low resistivity films. We conclude that the high noise level in YBCO is most likely intrinsic to the structure and due to conduction along the Cu‐O chains. Therefore, the low noise power in high resistivity films appears to indicate a degraded chain conductivity. © 1995 American Institute of Physics.
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74.72.-h Cuprate superconductors
74.78.-w Superconducting films and low-dimensional structures
74.25.F- Transport properties

Direct jointing of Ba–Sr–Ca–Cu–O superconducting glass‐ceramics by welding

Toshihiro Kasuga, Koichi Nakamura, Yoshihiro Abe, Eikichi Inukai, Shigeo Nagaya, and Naoki Hirano

Appl. Phys. Lett. 67, 136 (1995); http://dx.doi.org/10.1063/1.115508 (2 pages) | Cited 1 time

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Superconducting glass‐ceramics in the Bi–Sr–Ca–Cu–O (BSCCO) system were found to be successfully joined together by welding with an LNG‐O2 flame. Two edge portions of the glass‐ ceramics to be joined were set in close contact to each other and melted by the high‐temperature flame. After the welding, the joined portion was annealed with a soft flame, so that no crack formed in the product. The directly joined product was converted into a superconductor with Tc≂90 K by a postheating at ∼830 °C. Its critical current density Jc, was almost the same as the of the original glass‐ceramic. This technique is very important for fabrication of large‐sized superconducting apparatus such as current leads or magnetic shields. © 1995 American Institute of Physics.
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74.72.-h Cuprate superconductors
06.60.Vz Workshop procedures (welding, machining, lubrication, bearings, etc.)

Novel design of rapid single flux quantum logic based on a single layer of a high‐Tc superconductor

V. K. Kaplunenko, Z. G. Ivanov, E. A. Stepantsov, T. Claeson, T. Holst, Z. J. Sun, R. Kromann, Y. Q. Shen, P. Vase, T. Freltoft, and E. Wikborg

Appl. Phys. Lett. 67, 138 (1995); http://dx.doi.org/10.1063/1.115472 (3 pages) | Cited 13 times

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We suggest a new design of rapid single flux quantum (RSFQ) logic circuits which is based on a single superconducting layer and does not require a superconducting ground plane. Small inductances of about 10 pH, obligatory for RSFQ circuits, are formed as narrow slits of widths comparable to the London penetration depth (≂0.15 μm). The design allows us to decrease the geometric size of the RSFQ cell. Test circuits with YBaCuO grain boundary junctions on asymmetric 32° Y– ZrO2 bicrystals were used to measure the slit inductance per unit length and the mutual inductance of neighboring slits. A typical inductance of a 0.4 μm slit was found to be 0.7–0.8 pH/μm. © 1995 American Institute of Physics.
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85.25.Cp Josephson devices
84.30.Sk Pulse and digital circuits
74.78.-w Superconducting films and low-dimensional structures

Crystal‐orientation dependence on magnetic circular dichroism spectra of MnSb epitaxial film

H. Akinaga, Y. Suzuki, K. Tanaka, K. Ando, and T. Katayama

Appl. Phys. Lett. 67, 141 (1995); http://dx.doi.org/10.1063/1.115474 (3 pages) | Cited 17 times

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We present the crystal‐orientation dependence of the magnetic circular dichroism (MCD) spectra of ferromagnetic (1101) and (0001) MnSb epitaxial films grown by molecular beam epitaxy on (001) GaAs and (0001) sapphire substrates, respectively, where very large anisotropy is clearly observed at around 3.0 and 4.7 eV. The anisotropy of the MCD spectra is discussed in connection with the magnetocrystalline anisotropy. © 1995 American Institute of Physics.
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78.20.Ls Magneto-optical effects
75.50.Cc Other ferromagnetic metals and alloys
75.70.Ak Magnetic properties of monolayers and thin films
78.20.Ek Optical activity

Measurement of the methyl radical concentration profile in a hot‐filament reactor

P. Zalicki, Y. Ma, R. N. Zare, E. H. Wahl, T. G. Owano, and C. H. Kruger

Appl. Phys. Lett. 67, 144 (1995); http://dx.doi.org/10.1063/1.115475 (3 pages) | Cited 32 times

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The spatial profile of methyl radical concentration in a hot‐filament reactor has been measured using cavity ring‐down spectroscopy (CRDS) at a wavelength of 213.9 nm for which the CH3 absorption cross section has been shown to be nearly independent of temperature. Methyl radicals are generated with a 25 mm long tungsten filament heated to 2400 K in a slowly flowing mixture of 0.6% CH4 in H2 (20 Torr total pressure). CRDS is employed to measure CH3 absorbance as a function of a distance perpendicular to the axis of the filament. The CH3 absorbance profiles do not change when the direction of the process gas flow through the reactor is reversed, which indicates cylindrical symmetry of the CH3 distribution about the filament. Consequently, the radial CH3concentration in the reactor is determined by Abel inversion of the CH3 absorbance profile. The CH3concentration peaks ∼4 mm from the filament (1.04×1014molecules/cm3). Methyl radicals decay rapidly as a function of a distance from the filament and disappear about 2 cm from the filament within our present detection sensitivity (3×1012molecules/cm3). © 1995 American Institute of Physics.
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82.80.Ms Mass spectrometry (including SIMS, multiphoton ionization and resonance ionization mass spectrometry, MALDI)
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