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19 Feb 1990

Volume 56, Issue 8, pp. 703-793

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Cathodoluminescence imaging of patterned quantum well heterostructures grown on nonplanar substrates by molecular beam epitaxy

E. M. Clausen, E. Kapon, E. Kapon, M. C. Tamargo, and D. M. Hwang

Appl. Phys. Lett. 56, 776 (1990); http://dx.doi.org/10.1063/1.102684 (3 pages) | Cited 14 times

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We report cathodoluminescence (CL) imaging and transmission electron microscopy (TEM) studies of patterned GaAs/AlAs quantum well (QW) heterostructures grown by molecular beam epitaxy on periodically corrugated substrates. Faceting and surface diffusion during crystal growth result in significant lateral variations in QW thickness which translate quantum size effects into lateral band‐gap patterning. The CL images directly display lateral periodic modulation in quantum well thickness and indicate the existence of two lateral potential wells formed at the bottom and apex of corrugations. Emission wavelengths are in agreement with TEM data on the patterned structures. Such periodic patterned QW heterostructures should be useful for the realization of arrayed one‐ and zero‐dimensional semiconductor quantum structures, particularly lateral superlattice heterostructures.
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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

Accelerated formation of 110 K high Tc phase in the Ca‐ and Cu‐rich Bi‐Pb‐Sr‐Ca‐Cu‐O system

Y. T. Huang, R. G. Liu, S. W. Lu, P. T. Wu, and W. N. Wang

Appl. Phys. Lett. 56, 779 (1990); http://dx.doi.org/10.1063/1.103315 (3 pages) | Cited 31 times

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The crystal structure and superconducting properties of the Bi‐Pb‐Sr‐Ca‐Cu‐O system with Ca‐ and Cu‐rich nominal composition were investigated. A nearly single‐phased 110 K high Tc superconductor can be obtained with 852 °C/20 h sintering from the starting composition of Bi1.7Pb0.4Sr1.6Ca2.4Cu3.6Oy. X‐ray diffraction patterns, resistivity measurement, diamagnetic susceptibility results, and scanning electron micrographs all indicate that the Ca‐ and Cu‐rich nominal composition would result in better superconducting properties than those of Ca:Sr=1:1 Bi‐Pb‐Sr‐Ca‐Cu‐O compounds in a much shorter sintering time.
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74.70.-b Superconducting materials other than cuprates
74.25.-q Properties of superconductors
61.66.Fn Inorganic compounds
74.10.+v Occurrence, potential candidates

Fabrication of Tl‐Ba‐Ca‐Cu‐O films by annealing rf‐sputtered Ba‐Ca‐Cu‐O films in thallium oxide vapors

S. I. Shah, N. Herron, C. R. Fincher, and W. L. Holstein

Appl. Phys. Lett. 56, 782 (1990); http://dx.doi.org/10.1063/1.103316 (3 pages) | Cited 8 times

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Thin, superconducting Tl‐Ba‐Ca‐Cu‐O films were grown using a two‐step fabrication process which involved the growth of Ba‐Ca‐Cu‐O films by reactive magnetron sputtering followed by ex situ high‐temperature crystallization and thallination under thallium oxide vapors. Films were thallinated with both Tl2O3 and Tl2Ba2CuO6 as the source for thallium oxide vapors. Highly oriented films were obtained with the c axis perpendicular to the surface of the film. Best films had a Tc (R=0) of 104 K and a critical current density of 5×104 A/cm2 at 77 K.
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74.78.-w Superconducting films and low-dimensional structures
74.70.-b Superconducting materials other than cuprates
81.15.Cd Deposition by sputtering
74.25.Sv Critical currents

Properties of epitaxial YBa2Cu3O7 thin films on Al2O3 {1012}

K. Char, D. K. Fork, T. H. Geballe, S. S. Laderman, R. C. Taber, R. D. Jacowitz, F. Bridges, G. A. N. Connell, and J. B. Boyce

Appl. Phys. Lett. 56, 785 (1990); http://dx.doi.org/10.1063/1.103317 (3 pages) | Cited 44 times

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Epitaxial YBa2Cu3O7 films were grown on Al2O3 {1012} by a laser ablation technique. X‐ray diffraction shows that films are epitaxial with the c axis perpendicular to the substrate surface and ‘‘123’’ [110] aligned with sapphire [1011], although the full width at half maximum of the rocking curve is larger than those of epitaxial films on SrTiO3. Typical Tc’s are between 85 and 88 K with transition widths between 0.5 and 3 K. The normal‐state resistivity is 270 μΩ cm at 300 K and extrapolates to zero at zero temperature while the magnetization Jc is as high as 5×106 A/cm2 at 4.2 K. High‐frequency loss measurements show that 2000‐Å‐thick epitaxial films on Al2O3 {1012} have a surface impedance about 1 mΩ at 13 GHz at 4.2 K.
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74.78.-w Superconducting films and low-dimensional structures
74.70.-b Superconducting materials other than cuprates
68.55.-a Thin film structure and morphology
74.25.-q Properties of superconductors

Observations of quasi‐particle tunneling and Josephson behavior in Y1Ba2Cu3O7−x/ native barrier/Pb thin‐film junctions

J. Kwo, T. A. Fulton, M. Hong, and P. L. Gammel

Appl. Phys. Lett. 56, 788 (1990); http://dx.doi.org/10.1063/1.103318 (3 pages) | Cited 17 times

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Low‐leakage, thin‐film planar tunnel junctions made of Y1Ba2Cu3O7−x/ native barrier/Pb were fabricated. The Y1Ba2Cu3O7−x films were prepared by in situ molecular beam epitaxy aided with an activated oxygen source. The as‐grown, smooth superconducting perovskite film surface exhibits quasi‐particle tunneling characteristics very similar to the etched bulk single‐crystal data. The results in agreement are a linear dependence of the normal‐state conductance on voltage, a gap‐like structure at ∼20 mV, asymmetric modulations up to 50 mV, and a finite zero‐bias conductance at low temperature. Junctions of lower resistance show, at temperatures below Tc of Pb, the development of a supercurrent at zero bias and associated hysteretic subgap structure, with a typical IcR ∼0.5 mV. Josephson‐like behavior occurred in response to applied magnetic field and microwaves.
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74.50.+r Tunneling phenomena; Josephson effects
74.70.-b Superconducting materials other than cuprates
74.20.Mn Nonconventional mechanisms
74.20.Rp Pairing symmetries (other than s-wave)
74.78.-w Superconducting films and low-dimensional structures

Attenuation at a wavelength of 0.86 cm due to fibrous aerosols

C. W. Bruce, D. R. Ashmore, P. C. Pittman, N. E. Pedersen, J. C. Pedersen, and P. C. Waterman

Appl. Phys. Lett. 56, 791 (1990); http://dx.doi.org/10.1063/1.102667 (2 pages) | Cited 9 times

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Extinction efficiency was measured for fibrous aerosol particles arrayed on a diaphragm in a plane orthogonal to the Poynting vector of the incident radiation. Very small quantities of material can be characterized in this static fashion. Two‐dimensional extinction efficiencies for a series of graphitic fibers of various resistivities are shown to agree with results of a variational theory. Particle interaction distances initiate at approximately the value of the length of the particle.
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42.68.Ge Effects of clouds and water; ice crystal phenomena
42.68.Kh Effects of air pollution
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
78.70.Gq Microwave and radio-frequency interactions
FREE

Erratum: Rapid heteroepitaxial growth of Ge films on (100) GaAs by pulsed supersonic free‐jet chemical beam epitaxy [Appl. Phys. Lett. 55, 1008 (1989)]

Djula Eres, D. H. Lowndes, and J. Z. Tischler

Appl. Phys. Lett. 56, 793 (1990); http://dx.doi.org/10.1063/1.103336 (1 page)

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Abstract Unavailable
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81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
99.10.Cd Errata
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