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9 Oct 1989

Volume 55, Issue 15, pp. 1489-1584

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Barrier tuning by means of a quantum, interface‐induced dipole in a doping layer

G. Müller, A. Zrenner, F. Koch, and K. Ploog

Appl. Phys. Lett. 55, 1564 (1989); http://dx.doi.org/10.1063/1.102245 (3 pages) | Cited 10 times

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We consider a sharply defined doping layer near the interface of a heterostructure on the narrow‐gap side. It is shown that an interface‐induced dipole moment results, whose magnitude depends on the quantum spread of the electronic charge. The result of thermionic emission measurement of the barrier height is compared with a self‐consistent, nonparabolic subband calculation.
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73.40.Lq Other semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
79.40.+z Thermionic emission
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
73.61.Ey III-V semiconductors

Dislocations in In0.1Ga0.9As/GaAs multilayers epitaxially grown on Si substrates

Tatsuo Morita, M. Furukawa, M. Shimizu, Y. Nakajima, and T. Sakurai

Appl. Phys. Lett. 55, 1567 (1989); http://dx.doi.org/10.1063/1.102246 (2 pages) | Cited 1 time

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Dislocations in In0.1Ga0.9As/GaAs multilayers grown on Si substrates have been examined by using transmission electron microscopy. It is found that two types of misfit dislocations exist at the interfaces of multilayers which are composed of layers thicker than the critical thickness (hc). One is a 60° dislocation and the other is a pure edge dislocation. It is considered that a 60° dislocation can glide to adjacent layers from the interface, while a pure edge dislocation can also go out of the interface. The stress field caused by closely located dislocations introduces bowing of dislocation lines followed by cross slipping.
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68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties
68.35.Dv Composition, segregation; defects and impurities
61.72.Ff Direct observation of dislocations and other defects (etch pits, decoration, electron microscopy, x-ray topography, etc.)

Highly oriented Bi(Pb)‐Sr‐Ca‐Cu‐O superconducting thin films by magnetron sputtering of a single target

Y. Hakuraku, S. Higo, and T. Ogushi

Appl. Phys. Lett. 55, 1569 (1989); http://dx.doi.org/10.1063/1.102307 (3 pages) | Cited 12 times

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Superconducting Bi(Pb)‐Sr‐Ca‐Cu‐O thin films have been prepared onto (100) MgO substrates by dc magnetron sputtering using a single sintered target. The targets used were Bi2.7 ,Pbx Sr2 Ca2.25 Cu3.75 Oy (x=1.5, 1.75, 2.0, 2.25 and 2.5) in nominal composition. All the films were deposited at 400 °C and annealed at 850 °C for 3 h in air. Although the superconducting properties of the thin films were very sensitive to the Pb content of the target, reproducible results were obtained. After deposition from the target with x=2.0 and subsequent high‐temperature annealing, we have succeeded in obtaining highly c‐axis oriented thin films which have shown zero resistivity at 115 K. This may be due to the optimum substitution of Pb for Bi in addition to the conditions during the high‐temperature process. The average cationic ratio of the film was shown to be Bi:Pb:Sr:Ca:Cu=1.75:0.17:2:2.1:3.2 by electron‐probe x‐ray microanalysis.
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74.78.-w Superconducting films and low-dimensional structures
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
81.15.Cd Deposition by sputtering

Glass‐derived superconducting ceramics with zero resistance at 107 K in the Bi1.5Pb0.5Sr2Ca2Cu3Ox system

Narottam P. Bansal and D. E. Farrell

Appl. Phys. Lett. 55, 1572 (1989); http://dx.doi.org/10.1063/1.102308 (3 pages) | Cited 7 times

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A melt of composition Bi1.5Pb0.5Sr2Ca2Cu3Ox was fast quenched to form a glass. This was subsequently air annealed and the influence of annealing time and temperature on the formation of various crystalline phases was investigated. X‐ray powder diffraction indicated that none of the resulting samples were single phase. However, for an annealing temperature of 840 °C, the volume fraction of the high Tc phase (isostructural with Bi2 Sr2 Ca2 Cu3O10 ) increased with annealing time. A specimen annealed at this temperature for 243 h followed by slow cooling showed a sharp transition [ΔTc (10–90%) ∼2 K] and Tc (R=0)=107.2 K. To our knowledge, this is the highest Tc yet reported for any superconductor prepared via the glass route.
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74.25.Sv Critical currents
74.62.Bf Effects of material synthesis, crystal structure, and chemical composition
81.40.Rs Electrical and magnetic properties related to treatment conditions
74.70.-b Superconducting materials other than cuprates
81.05.Je Ceramics and refractories (including borides, carbides, hydrides, nitrides, oxides, and silicides)

Shock wave induced changes in superconductivity in YBa2Cu3O7−δ

L. E. Murr, C. S. Niou, S. Jin, T. H. Tiefel, A. C. W. P. James, R. C. Sherwood, and T. Siegrist

Appl. Phys. Lett. 55, 1575 (1989); http://dx.doi.org/10.1063/1.102309 (3 pages) | Cited 15 times

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Shock wave loading produced significant changes in superconductivity in sintered YBa2Cu3O7−δ causing a broad transition with Tc(R=0)∼40 K. The normal‐state resistivity increased by 20–50× with the ρ‐T curve exhibiting a semiconducting behavior. Comparative thermogravimetric analysis, however, indicated no loss of oxygen (δ∼0.1) in the shock‐loaded sample, and x‐ray powder diffraction analysis showed no major changes except for slight line broadening. The observed semiconductive behavior and degredation in superconductivity is thus attributed to a rather subtle disturbance in crystal structure, the nature of which is not clearly understood at present. The lack of sufficient recovery in Tc by post‐shock oxygen processing at temperatures as high as 750 °C and subsequent cooling implies that the atomic‐scale disturbance may not necessarily be related to a simple oxygen disorder. Such defects, if controlled properly, may be advantageously turned into desirable flux‐pinning sites for improved critical currents.
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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
81.40.Rs Electrical and magnetic properties related to treatment conditions
62.50.-p High-pressure effects in solids and liquids

Magnetic measurements of superconducting glass‐ceramic fine rods in Bi1Ca1Sr1Cu2Al0.5Ox prepared under a temperature gradient

Yutaka Higashida, Hisanori Yokoyama, Kazuo Michishita, Yukio Kubo, Hiroshi Yoshida, Yoshihiro Abe, and Hideo Hosono

Appl. Phys. Lett. 55, 1578 (1989); http://dx.doi.org/10.1063/1.102310 (3 pages) | Cited 8 times

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It is shown that the crystallization of the glass precursor under a temperature gradient is very effective for preparing the superconducting glass ceramics in the Bi‐Ca‐Sr‐Cu‐O system. The magnetization measurements show that the specimen prepared under a temperature gradient has a magnetization hysteresis several times larger at 4.2 K than that prepared under no temperature gradient; the coupling between superconducting grains of the former is stronger than that of the latter.
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74.81.Bd Granular, melt-textured, amorphous, and composite superconductors
74.70.-b Superconducting materials other than cuprates
74.25.Ha Magnetic properties including vortex structures and related phenomena
81.40.Rs Electrical and magnetic properties related to treatment conditions

Superconducting properties of Ba2YCu3O7−x thin films prepared by chemical vapor deposition on SrTiO3 and a metal substrate

Taichi Yamaguchi, Shinya Aoki, Nobuyuki Sadakata, Osamu Kohno, and Hiroshi Osanai

Appl. Phys. Lett. 55, 1581 (1989); http://dx.doi.org/10.1063/1.102311 (2 pages) | Cited 23 times

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Superconducting Ba2 YCu3 O7−x thin films were prepared by chemical vapor deposition using β‐diketonate chelates on SrTiO3 single crystalline substrates, metal substrates, and metal substrates with a polycrystalline SrTiO3 buffer. The temperatures of complete superconducting transitions were observed at 89, 81, and 84 K, respectively. Reduced critical current density of the film on a single crystalline substrate in magnetic fields up to 600 mT at 77 K remained one or two orders of magnitude higher than that of powder metallurgical processed specimens. According to x‐ray diffraction patterns, the existence of a well‐oriented orthorhombic Ba2 YCu3 O7−x structure has been confirmed in all specimens.
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74.78.-w Superconducting films and low-dimensional structures
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
74.70.-b Superconducting materials other than cuprates
61.66.Fn Inorganic compounds

New high‐efficiency quasi‐continuous operation of an ArF(B→X) excimer lamp excited by microwave discharge

Hiroshi Kumagai and Minoru Obara

Appl. Phys. Lett. 55, 1583 (1989); http://dx.doi.org/10.1063/1.102247 (2 pages) | Cited 23 times

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A quasi‐continuous ArF(193 nm:B→X) fluorescence of over 8 ms pulse duration with 100 Hz operation frequency was observed in a microwave‐discharge‐pumped ArF lamp. The average ArF fluorescence power was 29 W obtained with an intrinsic efficiency of 4.4% with a 655 W average microwave power deposition. A peak ArF fluorescence power of 53 W with a power efficiency of 5.5% was also obtained.
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52.80.Pi High-frequency and RF discharges
52.75.-d Plasma devices
42.72.-g Optical sources and standards
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