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17 Aug 1987

Volume 51, Issue 7, pp. 469-551

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Compact, multipass, single transverse mode CO2 laser

J. G. Xin and D. R. Hall

Appl. Phys. Lett. 51, 469 (1987); http://dx.doi.org/10.1063/1.98396 (3 pages) | Cited 7 times

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We report the design and basic operating characteristics of a co‐axial radio‐frequency discharge carbon dioxide laser which employs a multipass Herriott cell folding system within a linear resonator. A continuous wave laser power output of 65 W was obtained from a device 35 cm in length in a high‐quality TEM00 mode without gas flow. The characteristics of transverse rf discharges and the image rotation properties of such resonators indicate that this approach may be scalable to provide much higher laser powers with excellent transverse mode properties.
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42.60.By Design of specific laser systems
42.60.Da Resonators, cavities, amplifiers, arrays, and rings
42.60.Jf Beam characteristics: profile, intensity, and power; spatial pattern formation
42.55.Lt Gas lasers including excimer and metal-vapor lasers

Surface‐emitting distributed feedback semiconductor laser

S. H. Macomber, J. S. Mott, R. J. Noll, G. M. Gallatin, E. J. Gratrix, S. L. O’Dwyer, and S. A. Lambert

Appl. Phys. Lett. 51, 472 (1987); http://dx.doi.org/10.1063/1.98397 (3 pages) | Cited 20 times

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Electrically pumped, surface‐emitting distributed feedback lasers were for the first time demonstrated without any facet reflections. The devices contained second‐order gratings etched into a thin p‐AlGaAs cladding layer surface. A gold ohmic contact deposited directly onto the p‐AlGaAs grating surface provided strong coupling to the waveguide mode. Single spatial mode devices with low divergence output beams and single frequency spectra were obtained at room temperature.
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42.55.Px Semiconductor lasers; laser diodes
42.60.Da Resonators, cavities, amplifiers, arrays, and rings

Optical bistability and nonlinear switching due to increasing absorption in single‐crystal ZnSe waveguides

B. G. Kim, E. Garmire, N. Shibata, and S. Zembutsu

Appl. Phys. Lett. 51, 475 (1987); http://dx.doi.org/10.1063/1.98398 (3 pages) | Cited 13 times

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Optical nonlinear switching and bistability due to increasing absorption have been observed in single‐crystal ZnSe waveguides with contrast ratios of 16/1 and switching times of 10 μs at 15 mW of argon laser light. Switching energy is improved over the bulk by a factor of 200.
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42.79.Gn Optical waveguides and couplers
42.65.Pc Optical bistability, multistability, and switching, including local field effects
42.82.-m Integrated optics
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)

Observation of quantum‐size effects in optical transmission spectra of PbTe/Pb1−xEuxTe superlattices

Akihiro Ishida, Shuji Matsuura, Makoto Mizuno, and Hiroshi Fujiyasu

Appl. Phys. Lett. 51, 478 (1987); http://dx.doi.org/10.1063/1.98372 (3 pages) | Cited 18 times

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Optical transmission spectra of PbTe/Pb1−xEuxTe (x=0.05) superlattices were measured at 300 K. The superlattices were prepared on thick Pb1−xEuxTe buffers grown on KCl (100) substrates using the hot wall epitaxy technique. Clear steplike absorptions corresponding to the interband electron transitions between subbands (n=1,2,3 to n=1,2,3) were observed for the first time for the PbTe/Pb1−xEuxTe superlattice. The experimental absorption edges agreed very well with theoretical ones calculated assuming the conduction‐band offset is equal to that of the valence band.
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78.66.Fd III-V semiconductors
78.66.Hf II-VI semiconductors
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties

Cr‐ and Cu‐polyimide interface: Chemistry and structure

R. C. White, R. Haight, B. D. Silverman, and P. S. Ho

Appl. Phys. Lett. 51, 481 (1987); http://dx.doi.org/10.1063/1.98373 (3 pages) | Cited 22 times

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High‐resolution x‐ray and ultraviolet photoemission spectroscopies have been applied to study the initial formation of the Cr‐ and Cu‐polyimide interfaces. A model for the growth modes of these two interfaces is proposed based on comparison of experimental results with trends derived from quantum‐chemical calculations.
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68.35.Fx Diffusion; interface formation
82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces
79.60.Jv Interfaces; heterostructures; nanostructures

Atomic force microscopy of liquid‐covered surfaces: Atomic resolution images

O. Marti, B. Drake, and P. K. Hansma

Appl. Phys. Lett. 51, 484 (1987); http://dx.doi.org/10.1063/1.98374 (3 pages) | Cited 120 times

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Images of graphite surfaces that are covered with oil reveal the hexagonal rings of carbon atoms. Images of a sodium chloride surface, protected from moisture by oil, exhibit a monoatomic step. Together, these images demonstrate the potential of atomic force microscopy (AFM) for studying both conducting and nonconducting surfaces, even surfaces covered with liquids. Our AFM uses a cross of double wires with an attached diamond stylus as a force sensor. The force constant is ≊40 N/m. The resonant frequency is ≊3 kHz. The lateral and vertical resolutions are 0.15 nm and 5 pm.
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07.79.Cz Scanning tunneling microscopes
61.05.-a Techniques for structure determination
68.35.B- Structure of clean surfaces (and surface reconstruction)
68.08.-p Liquid-solid interfaces
68.43.-h Chemisorption/physisorption: adsorbates on surfaces
68.35.Gy Mechanical properties; surface strains

Implantation damage and the anomalous transient diffusion of ion‐implanted boron

A. E. Michel, W. Rausch, and P. A. Ronsheim

Appl. Phys. Lett. 51, 487 (1987); http://dx.doi.org/10.1063/1.98375 (3 pages) | Cited 55 times

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The effect of the implantation of silicon ions on the anomalous transient diffusion of ion‐implanted boron is investigated. It is found that silicon ion fluences well below that necessary to amorphize the lattice substantially reduce the anomalous transient diffusion of subsequently implanted boron. The sheet resistance, however, is increased by the additional silicon implant. The implantation of silicon ions into activated boron layers causes additional anomalous diffusion at substantial distances beyond the range of the silicon ions. The anomalous motion is also reduced in regions where the damage is greater. The effects can be explained in terms of the generation of point defect clusters which dissolve during anneal and the sinking of point defects in the regions of high damage by the formation of interstitial type extended defects.
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66.30.J- Diffusion of impurities
61.72.uf Ge and Si
73.40.Kp III-V semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
61.80.Jh Ion radiation effects

Permeation of hydrogen into silicon during low‐energy hydrogen ion beam bombardment

M. W. Horn, J. M. Heddleson, and S. J. Fonash

Appl. Phys. Lett. 51, 490 (1987); http://dx.doi.org/10.1063/1.98376 (3 pages) | Cited 15 times

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In this study we examine the permeating of hydrogen into p‐type silicon during low‐energy hydrogen ion beam bombardment by monitoring boron doping deactivation. This examination is done for various times and two different exposure temperatures. In addition we explore the effect of temperature during subsequent isochronal anneals on the recovery of silicon exposed to a hydrogen ion beam. As a result of these studies, it is found that there are two distinct permeation regions. Each may be characterized by its own apparent diffusion coefficient, activation energy, and recovery process.
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61.80.Jh Ion radiation effects
66.30.J- Diffusion of impurities

Electric field dependent exciton energy and photoluminescence quenching in GaInAs/InP quantum wells

M. G. Shorthose, A. C. Maciel, J. F. Ryan, M. D. Scott, A. Moseley, J. I. Davies, and J. R. Riffat

Appl. Phys. Lett. 51, 493 (1987); http://dx.doi.org/10.1063/1.98377 (3 pages) | Cited 12 times

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We report the observation of electric field induced exciton energy shifts and photoluminescence quenching in GaInAs/InP multiple quantum wells. We have measured both the photocurrent and photoluminescence spectra from 100 Å wells contained with p+‐ and n+‐InP layers in a conventional p‐i‐n structure; reverse bias voltages of up to 12 V were applied. The exciton peaks in the photocurrent spectrum are seen to broaden and shift to lower energy; the photoluminescence peak, which is due to n=1 excitonic and free‐carrier recombination, also shifts to lower energy and is completely quenched at high voltages. These results are similar to those reported previously for GaAs quantum wells and ascribed to the quantum‐confined Stark effect.
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73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
78.55.Cr III-V semiconductors
73.50.Pz Photoconduction and photovoltaic effects
73.40.Kp III-V semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions

Hydrogenation of GaAs on Si: Effects on diode reverse leakage current

S. J. Pearton, C. S. Wu, Michael Stavola, F. Ren, J. Lopata, W. C. Dautremont‐Smith, S. M. Vernon, and V. E. Haven

Appl. Phys. Lett. 51, 496 (1987); http://dx.doi.org/10.1063/1.98378 (3 pages) | Cited 34 times

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Plasma hydrogenation for 3 h at 250 °C of GaAs layers grown directly on Si substrates by metalorganic chemical vapor deposition, followed by a 5‐min, 400 °C anneal to restore the passivated shallow donor electrical activity, increases the reverse breakdown voltage of Schottky diode structures from 2.5 to 6.5 V. This improvement appears to be a result of the passivation by atomic hydrogen of defects such as threading dislocations caused by the large (4%) lattice mismatch between GaAs and Si. A reduced Schottky barrier height is exhibited by hydrogenated samples, consistent with As depletion of the surface occurring during the long duration plasma processing.
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73.30.+y Surface double layers, Schottky barriers, and work functions
73.61.Ey III-V semiconductors
81.15.Kk Vapor phase epitaxy; growth from vapor phase
81.65.-b Surface treatments

Polarization‐dependent optical gain and absorption spectra of (Cd,Mn)Te and (Zn,Mn)Se multiple quantum well structures

T. C. Bonsett, M. Yamanishi, R. L. Gunshor, S. Datta, and L. A. Kolodziejski

Appl. Phys. Lett. 51, 499 (1987); http://dx.doi.org/10.1063/1.98988 (3 pages) | Cited 5 times

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The absorption and gain spectra for TE and TM modes in (100) oriented (Cd,Mn)Te and (Zn,Mn)Se multiple quantum well (MQW) structures have been measured by observing the photoluminescence from a cleaved edge. In (Cd,Mn)Te MQW’s the TE mode absorption and gain are dominant, as observed earlier in (Ga,Al)As MQW’s; in (Zn,Mn)Se MQW’s, however, we observe a clear dominance of the TM mode near the band edge. Whereas the TE mode dominates the gain spectra of a (Cd,Mn)Te MQW, the TM mode dominates the gain spectra of a (Zn,Mn)Se MQW, providing the first report of TM‐polarized stimulated emission from a MQW structure. The opposite behavior of (Cd,Mn)Te and (Zn,Mn)Se MQW’s is ascribed to the opposite sense of the uniaxial strain in these systems.
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78.66.Fd III-V semiconductors
78.66.Hf II-VI semiconductors
78.45.+h Stimulated emission
78.40.Fy Semiconductors
78.55.Et II-VI semiconductors

Electrolyte electroreflectance of HgCdTe at low temperatures

L. E. A. Berlouis, L. M. Peter, M. G. Astles, and R. G. Humphreys

Appl. Phys. Lett. 51, 502 (1987); http://dx.doi.org/10.1063/1.98379 (3 pages) | Cited 7 times

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Electrolyte electroreflectance measurements in ethanol/lithium perchlorate solutions over the temperature range 300–156 K have been used to derive the temperature dependence of the E1 transition of Hg1−xCdxTe (x=0.23–0.36). The temperature coefficient dE1/dT derived by third derivative line‐shape fitting (6.6±0.5×10−4 eV K−1) is considerably higher than values reported previously in the literature.
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78.20.Jq Electro-optical effects
73.40.Mr Semiconductor-electrolyte contacts

Dependence of the AlxGa1−xAs band edge on alloy composition based on the absolute measurement of x

T. F. Kuech, D. J. Wolford, R. Potemski, J. A. Bradley, K. H. Kelleher, D. Yan, J. Paul Farrell, P. M. S. Lesser, and F. H. Pollak

Appl. Phys. Lett. 51, 505 (1987); http://dx.doi.org/10.1063/1.98380 (3 pages) | Cited 98 times

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The absolute determination of the Al concentration, x, in epitaxial layers of AlxGa1−xAs was carried out using a nuclear reaction technique. This technique utilizes the narrow resonances found in the 27Al( p,γ)Si28 reaction, together with Rutherford backscattering measurements, to obtain accurate values of the alloy composition. The AlxGa1−xAs band edge was measured on these samples through low‐temperature photoluminescence (2 K) measurements. An improved value of the direct edge (Γ) on composition was determined to be EΓg =1.512 +1.455x(eV) within a ±0.3% limit. The direct‐to‐indirect transition was found to occur at an Al concentration of x≂0.37±0.015, lower than previously reported for He temperatures.
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68.55.Nq Composition and phase identification
78.70.Dm X-ray absorption spectra
78.66.Fd III-V semiconductors
78.66.Hf II-VI semiconductors
78.55.Cr III-V semiconductors

New effects of structure in momentum and real space on nonlinear transport across heterojunction band discontinuities

Kiwook Kim, Karl Hess, and Federico Capasso

Appl. Phys. Lett. 51, 508 (1987); http://dx.doi.org/10.1063/1.98381 (3 pages) | Cited 6 times

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Nonlinear transport across heterojunction band discontinuities in strong electric fields is theoretically investigated. New phenomena which depend on the combined effects of the structure in real and momentum space are found. Reflections at the heterointerfaces, carrier overheating at the potential step, and the L→Γ, X→Γ backscattering bottlenecks produce pronounced peaks and anisotropies in the energy and momentum distributions, respectively. Finally, a new ionization rate overshoot effect due to the band structure difference between the two materials is discussed.
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73.40.Kp III-V semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
73.50.Fq High-field and nonlinear effects
73.50.Gr Charge carriers: generation, recombination, lifetime, trapping, mean free paths
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems

Optical characterization of semi‐insulating GaAs: Determination of the Fermi energy, the concentration of the midgap EL2 level and its occupancy

J. Lagowski, M. Bugajski, M. Matsui, and H. C. Gatos

Appl. Phys. Lett. 51, 511 (1987); http://dx.doi.org/10.1063/1.98382 (3 pages) | Cited 13 times

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The key electronic characteristics of semi‐insulating GaAs, i.e., the Fermi energy, concentration, and occupancy of the midgap donor EL2, and the net concentration of ionized acceptors can all be determined from high‐resolution measurements of the EL2 intracenter absorption. The procedure is based on the measurement of zero‐phonon line intensity before and after the complete transfer of EL2 to its metastable state followed by thermal recovery. The procedure is quantitative, involves no fitting parameters, and unlike existing methods, is applicable even when a significant part of the EL2 is ionized.
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78.30.-j Infrared and Raman spectra
78.40.Fy Semiconductors
71.18.+y Fermi surface: calculations and measurements; effective mass, g factor
71.55.Eq III-V semiconductors
61.72.sd Impurity concentration
61.72.sh Impurity distribution
61.72.sm Impurity gradients

Si‐SiO2 interface trap production by low‐temperature thermal processing

Michael L. Reed and James D. Plummer

Appl. Phys. Lett. 51, 514 (1987); http://dx.doi.org/10.1063/1.98383 (3 pages) | Cited 23 times

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Post‐metal annealing of aluminum gate metal‐oxide‐semiconductor capacitors can produce, as well as anneal, interface traps at the Si‐SiO2 interface. The production mechanism is shown to be a thermal decomposition of passivated traps. Mechanisms involving interactions with atomic or molecular hydrogen are inconsistent with the experimental data.
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73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
73.50.Gr Charge carriers: generation, recombination, lifetime, trapping, mean free paths
85.30.De Semiconductor-device characterization, design, and modeling

Temperature‐dependent damage production in ion‐implanted strained‐layer superlattices

D. R. Myers, G. W. Arnold, L. R. Dawson, R. M. Biefeld, C. R. Hills, and B. L. Doyle

Appl. Phys. Lett. 51, 517 (1987); http://dx.doi.org/10.1063/1.98384 (3 pages) | Cited 8 times

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We have characterized damage production in both (InGa)As/GaAs and Ga(AsP)/GaP strained‐layer superlattices (SLS’s) for fluences sufficient to induce compositional disordering at three different implant temperatures. Dramatically different implant temperatures are required to produce similar defect distributions between the two SLS systems. Implants at lower temperatures [80 K for the (InGa)As/GaAs system, 300 K and below for the Ga(AsP)/GaP system] exhibit amorphous zones at depths consistent with the predictions of ion range codes; while implants at elevated temperatures [25 °C in (InGa)As/GaAs, 400 °C in the Ga(AsP)/GaP system] exhibit greatly reduced damage levels characterized mainly by extended defects.
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61.80.Jh Ion radiation effects
68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.

Novel oxidation process in Ge+‐implanted Si and its effect on oxidation kinetics

O. W. Holland, C. W. White, and D. Fathy

Appl. Phys. Lett. 51, 520 (1987); http://dx.doi.org/10.1063/1.98385 (3 pages) | Cited 66 times

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Thermal oxidation of Si is shown to be substantially affected by the implantation of Ge+ ions. A unique morphology develops during steam oxidation due to the rejection of Ge from the oxide at the growth interface. The Ge pile‐up leads to the formation of a distinct layer of almost pure Ge between the oxide and the underlying Si. Oxidation rates are enhanced due to the presence of this film which is shown to increase the interfacial reaction rate. This increase is attributed to a decrease in the binding energy of Si atoms at the interface as a result of alloying with the Ge film. A model is proposed to account for the enhanced oxidation kinetics and is shown to be in good agreement with experimental data.
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81.65.-b Surface treatments
68.35.Fx Diffusion; interface formation
82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces
61.72.uf Ge and Si

Formation of the interface between GaAs and Si: Implications for GaAs‐on‐Si heteroepitaxy

R. D. Bringans, Marjorie A. Olmstead, R. I. G. Uhrberg, and R. Z. Bachrach

Appl. Phys. Lett. 51, 523 (1987); http://dx.doi.org/10.1063/1.98386 (3 pages) | Cited 27 times

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Results of photoemission core‐level spectroscopy measurements for coverages of around one monolayer of As, Ga, and GaAs on Si substrates are presented. The interfaces were formed on on‐axis Si(100) and Si(111) substrates using molecular beam epitaxy techniques. The bonding between As and the substrate surface leaves the As atoms fully coordinated and thus extremely unreactive. This causes the GaAs films to form islands at average coverages of less than one monolayer. The surface between the islands is found to be terminated by a single atomic layer of As. Use of a Ga predeposition technique shows evidence of decreasing the area between islands. Results for As interaction with stepped Si(100) surfaces and the implications for avoidance of antiphase domain boundaries are discussed.
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68.35.Fx Diffusion; interface formation
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
68.35.B- Structure of clean surfaces (and surface reconstruction)
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems

Negative transconductance resonant tunneling field‐effect transistor

Federico Capasso, Susanta Sen, and Alfred Y. Cho

Appl. Phys. Lett. 51, 526 (1987); http://dx.doi.org/10.1063/1.98387 (3 pages) | Cited 6 times

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The operation of a new resonant tunneling transistor is reported. The field‐effect transistorlike structure contains a double barrier in the gate. Resonant tunneling through the gate can be quenched by varying the drain or gate bias, leading respectively to negative conductance and negative transconductance in the drain current. Dramatic differences in the negative conductance and transconductance regions of the current‐voltage characteristic are observed for opposite bias polarities. This different behavior directly demonstrates the role, in controlling resonant tunneling, of the electron accumulation and depletion layers in the channel adjacent to the double barrier.
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85.30.Mn Junction breakdown and tunneling devices (including resonance tunneling devices)
85.30.Tv Field effect devices
73.30.+y Surface double layers, Schottky barriers, and work functions
73.40.Gk Tunneling

Molecular stream epitaxy of ultrathin InGaAs/GaAsP superlattices

T. Katsuyama, M. A. Tischler, N. H. Karam, N. El‐Masry, and S. M. Bedair

Appl. Phys. Lett. 51, 529 (1987); http://dx.doi.org/10.1063/1.98388 (3 pages) | Cited 6 times

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Molecular stream epitaxy allows several molecular beam epitaxy (MBE) concepts to take place in a metalorganic chemical vapor deposition reactor. In this technique, the growth of InGaAs/GaAsP superlattices proceeds by rotating the substrate between two gas streams, one containing trimethylgallium (TMG), triethylindium, and AsH3 and the other containing TMG, PH3, and AsH3. This technique eliminates gas flow transients and provides a method to mechanically shear off the gaseous boundary layer between successive exposures. Ultrathin strained‐layer superlattices (SLS’s) with 8‐Å‐thick films have been obtained. The optical properties of these SLS’s are comparable to those obtained for equivalent superlattices by gas source MBE.
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81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties
78.66.Fd III-V semiconductors
78.66.Hf II-VI semiconductors

Water interaction with the superconducting YBa2Cu3O7 phase

M. F. Yan, R. L. Barns, H. M. O’Bryan, P. K. Gallagher, R. C. Sherwood, and S. Jin

Appl. Phys. Lett. 51, 532 (1987); http://dx.doi.org/10.1063/1.98389 (3 pages) | Cited 208 times

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We show that the superconducting YBa2Cu3O7 phase is highly sensitive to water and water vapor. This is probably due to the presence of nonequilibrium Cu3+ ions in this compound. In particular, the YBa2Cu3O7 phase decomposes in water to CuO, Ba(OH)2 and Y2BaCuO5 and evolves oxygen. Samples with a reduced oxygen content, e.g., YBa2Cu3O6.0, also decompose in an aqueous ambient. The superconductivity of YBa2Cu3O7 samples is greatly degraded by the interaction with water and humid air. This effect should not preclude practical application of these materials since it should be possible to protect them with coatings of metal, glass, or plastic.
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81.40.Rs Electrical and magnetic properties related to treatment conditions
81.05.Je Ceramics and refractories (including borides, carbides, hydrides, nitrides, oxides, and silicides)
81.65.-b Surface treatments
74.70.-b Superconducting materials other than cuprates
82.30.Lp Decomposition reactions (pyrolysis, dissociation, and fragmentation)

Electron microscopy and microanalysis of a YBa2Cu3Ox superconducting oxide

S. X. Dou, A. J. Bourdillon, C. C. Sorrell, S. P. Ringer, K. E. Easterling, N. Savvides, J. B. Dunlop, and R. B. Roberts

Appl. Phys. Lett. 51, 535 (1987); http://dx.doi.org/10.1063/1.98390 (3 pages) | Cited 14 times

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The onset of superconductivity at 140 K has been observed in the high Tc Y‐Ba‐Cu‐O system in samples consisting of 90% by volume of a single‐phase oxide of average cation ratio Y:Ba:Cu≂1:2:3. A sharp superconducting transition in the resistivity has been measured, where Tc0=140 K, Tc=93.2 K, ΔTc=0.5 K, and ‘‘zero resistance’’ was observed at 92.0 K. Transmission electron microscopy and energy dispersive spectroscopy measurements revealed that the superconducting phase consisted of a large number of microcrystallites of ≂0.5 μm size and that these contained a very high defect microtwinned/faulted structure.
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74.10.+v Occurrence, potential candidates
74.70.-b Superconducting materials other than cuprates
74.25.Sv Critical currents
74.62.Bf Effects of material synthesis, crystal structure, and chemical composition
61.72.Mm Grain and twin boundaries

EuBa2Cu3Ox produced by oxidation of a rapidly solidified precursor alloy: An alternative preparation method for high Tc ceramic superconductors

R. Haldar, Y. Z. Lu, and B. C. Giessen

Appl. Phys. Lett. 51, 538 (1987); http://dx.doi.org/10.1063/1.98391 (2 pages) | Cited 29 times

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High‐temperature ceramic superconductors such as RE1Ba2Cu3O∼7 are usually prepared by reacting the constituent metal oxides (RE=rare‐earth metal). We have prepared RE1Ba2Cu3O∼7 by an alternate method, first combining three metals into an alloy by rapid solidification processing, followed by oxidation to form the cuprate. Only Eu (or Yb) yields single phase RE‐Ba‐Cu liquids as required for melt processing, because their valency changes from two in the metal (assuring complete miscibility with Ba) to three in the oxide. The superconducting properties of the oxidized alloys are similar to those of EuBa2Cu3Ox prepared by the standard ceramic reaction route.
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81.05.Je Ceramics and refractories (including borides, carbides, hydrides, nitrides, oxides, and silicides)
81.05.Bx Metals, semimetals, and alloys
74.70.-b Superconducting materials other than cuprates

Josephson effect above 77 K in a YBaCuO break junction

John Moreland, L. F. Goodrich, J. W. Ekin, T. E. Capobianco, A. F. Clark, A. I. Braginski, and A. J. Panson

Appl. Phys. Lett. 51, 540 (1987); http://dx.doi.org/10.1063/1.98392 (2 pages) | Cited 9 times

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We have observed the Josephson effect in a YBaCuO break junction. Critical currents as high as 10 mA were measured at 4 K for break junctions with a point contact within the fracture of a sample. The junction was susceptible to microwave radiation showing Shapiro steps with the ratio of V/f of 2.04±0.05 μV/GHz compared to the pair tunneling value of h/2e=2.068 μV/GHz. These steps were clearly visible in the current‐voltage characteristics at tempertures up to 85±5 K.
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74.50.+r Tunneling phenomena; Josephson effects
74.70.-b Superconducting materials other than cuprates
85.25.-j Superconducting devices
74.25.Sv Critical currents
74.62.Bf Effects of material synthesis, crystal structure, and chemical composition
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