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23 Jan 1989

Volume 54, Issue 4, pp. 295-400

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Identification of oxygen vacancies in YBaCuO superconductors by high‐resolution electron microscopy

Y. H. Liang, J. Chen, and D. Feng

Appl. Phys. Lett. 54, 368 (1989); http://dx.doi.org/10.1063/1.101452 (3 pages) | Cited 2 times

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High‐resolution electron microscopy studies as well as computer simulation studies on oxygen vacancies in Y‐Ba‐Cu‐O superconductors show that the existence of oxygen vacancies at {0, 1/2, 0} sites leads to the distortions of structural images. For certain imaging conditions, the spots corresponding to the column of oxygen vacancies can be distorted heavily, so that the indirect image of oxygen vacancies in Y‐Ba‐Cu‐O superconductors may be acquired. The results reveal that even in local area the oxygen vacancies may be distributed regularly.
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61.72.jd Vacancies
61.72.jj Interstitials
74.70.-b Superconducting materials other than cuprates
61.72.Ff Direct observation of dislocations and other defects (etch pits, decoration, electron microscopy, x-ray topography, etc.)
07.79.Cz Scanning tunneling microscopes
61.05.-a Techniques for structure determination

Oriented high Tc superconductive layers on silver by devitrification of glasses formed in the Bi‐Sr‐Ca‐Cu oxide system

R. C. Baker, W. M. Hurng, and H. Steinfink

Appl. Phys. Lett. 54, 371 (1989); http://dx.doi.org/10.1063/1.101453 (3 pages) | Cited 22 times

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Highly oriented crystalline layers of Bi4(Sr,Ca)3Cu4O16+x high Tc superconductors were produced by the devitrification of aerosol suspensions of glasses prepared from the mixed oxides when the suspensions were brought into rapid contact with heated silver substrates. The best magnetic susceptibility signals, produced by superconductivity at 77 K, were obtained when the glass was rapidly heated to about 850 °C from room temperature. The deposited layers are composed of a nearly pure superconductive phase in the form of flat platelets up to several hundred microns in diameter that are oriented with the c axis normal to the substrate. The addition of a small amount of Pb to the glass lowers the optimum deposition temperature and improves the crystal morphology.
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74.78.Fk Multilayers, superlattices, heterostructures
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

Observation of twin boundary layers in pure and alloyed YBa2Cu3O7−δ

Y. Zhu, M. Suenaga, Youwen Xu, R. L. Sabatini, and A. R. Moodenbaugh

Appl. Phys. Lett. 54, 374 (1989); http://dx.doi.org/10.1063/1.101349 (3 pages) | Cited 40 times

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Using an electron diffraction technique, the thicknesses of the (nonorthorhombic) twin boundary layers were measured for pure and alloyed YBa2(Cu1−xMx)3O7−δ. Boundary thickness varied from ∼0.7 nm for M=Ni, x=0.02, and δ≂0 to ∼2.6 nm for M=Al, x=0.02, and δ≂0, while it was ∼1.0 nm for a pure YBa2Cu3O7. High‐resolution transmission electron imaging of similar specimens supports the existence of such twin boundary layers.
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74.78.-w Superconducting films and low-dimensional structures
68.55.-a Thin film structure and morphology
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
74.25.Sv Critical currents

Cu valence and the formation of high Tc superconductor oxides studied by x‐ray photoemission spectroscopy on 200 Å Bi‐Sr‐Ca‐Cu oxide thin films

J.‐J. Yeh, S. B. DiCenzo, E. H. Hartford, M. Hong, and R. J. Felder

Appl. Phys. Lett. 54, 377 (1989); http://dx.doi.org/10.1063/1.100971 (3 pages) | Cited 11 times

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We have used x‐ray photoemission spectroscopy to study the core level spectra of 200 Å Bi‐Sr‐Ca‐Cu oxide thin films, in the hope that the importance of the surface sensitivity of photoemission is minimized for these samples, whose thickness is only 6–7 unit cells. The samples were annealed in oxygen at temperatures ranging from 600 to 870 °C, over which temperature range the thin films are converted from an amorphous insulating phase to an ordered superconducting phase with Tc (R=0)=80 K. Regardless of the annealing temperature, the Cu 2p spectra of all films show satellite structure indicative of Cu2+ states. Even the spectrum of an as‐deposited film has a satellite similar to those observed for the annealed films, including the superconducting film. The similarity of the satellite structure in the core level spectra for all films suggests that the Cu‐O interactions, such as the Cu d‐O p orbital charge transfer energies and the hopping integrals, remain similar when the oxides undergo the insulator‐superconductor transition through high‐temperature anneal. That is, the same local Cu‐O interaction exists before and after the superconducting phase sets in. This implies that the Cu valence alone does not determine the properties of high Tc superconductors.
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74.78.-w Superconducting films and low-dimensional structures
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
74.20.Mn Nonconventional mechanisms
74.20.Rp Pairing symmetries (other than s-wave)
73.20.At Surface states, band structure, electron density of states

c‐axis oriented YBa2Cu3O7−x superconducting films by metalorganic chemical vapor deposition

K. Zhang, B. S. Kwak, E. P. Boyd, A. C. Wright, and A. Erbil

Appl. Phys. Lett. 54, 380 (1989); http://dx.doi.org/10.1063/1.101378 (3 pages) | Cited 30 times

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Highly textured single phase superconducting YBa2Cu3O7−x films have been successfully grown on the yttria‐stabilized zirconia (100) substrates by using the metalorganic chemical vapor deposition technique. The as‐deposited films grown at 650 °C were homogeneous mixtures of the related metal oxides and carbonates. Subsequent thermal annealing under oxygen flow yielded single phase superconducting films whose thickness corresponded to the deposition rates of approximately 10 μm/h. After the post‐annealing the films deposited on the yttria‐stabilized zirconia substrates exhibited a highly textured x‐ray pattern with c axis perpendicular to the substrate surface. These films show an onset superconducting transition temperature of 93 K with the resistance becoming zero at 84 K.
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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.)
68.55.-a Thin film structure and morphology
74.70.-b Superconducting materials other than cuprates

Low‐temperature deposition of Y‐Ba‐Cu‐O films on a CaF2/GaAs substrate

K. Mizuno, M. Miyauchi, K. Setsune, and K. Wasa

Appl. Phys. Lett. 54, 383 (1989); http://dx.doi.org/10.1063/1.101379 (3 pages) | Cited 24 times

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Superconducting thin films of Y‐Ba‐Cu‐O were fabricated on a CaF2/GaAs(100) substrate using the rf planar magnetron sputtering technique. Substrates were heated as low as 450 °C during deposition. The as‐deposited films without high‐temperature post‐annealing have a transition temperature of 75 K and zero resistance temperature of 45 K. The perovskite structure usually observed in this system was not observed. The critical current (Jc) value of 2×103 A/cm2 was measured at 4.2 K.
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74.78.-w Superconducting films and low-dimensional structures
81.15.Cd Deposition by sputtering
74.70.-b Superconducting materials other than cuprates
74.25.Sv Critical currents

Hysteretic ac losses in high‐temperature superconductors

G. Kozlowski and X. Y. Chen

Appl. Phys. Lett. 54, 386 (1989); http://dx.doi.org/10.1063/1.101454 (3 pages) | Cited 4 times

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Theory of ac losses in the type II superconductors in the frame of the critical state model [J. Thompson, M. Maley, and J. R. Clem, J. Appl. Phys. 50, 3531, 3518 (1979)] is applied to high Tc materials (Y‐Ba‐Cu‐O) assuming an exponential drop of the critical current density Jc with both magnetic field and temperature. The dependence of dc magnetic field (H1) at which ac loss minimum occurs on an amplitude of ac magnetic field (h0) and on temperature Tc is calculated numerically. The two maxima of the total ac losses are found: one of them is very close to Tc and second maximum below Tc shifts to lower temperatures with increasing ac or dc magnetic field.
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74.25.N- Response to electromagnetic fields
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

Microwave surface resistance of bulk Tl‐Ba‐Ca‐Cu‐O superconductors

H. S. Newman, A. K. Singh, K. Sadananda, and M. A. Imam

Appl. Phys. Lett. 54, 389 (1989); http://dx.doi.org/10.1063/1.100972 (2 pages) | Cited 7 times

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The first measurements of the microwave surface resistance at 18 GHz of bulk Tl‐Ba‐Ca‐Cu‐O superconductors produced by the hot isostatic pressing (HIP) process are reported. The superconducting samples, prepared by solid‐state reaction with subsequent sintering and consolidation to obtain ideal density, were measured by replacing the end wall of a TE011 circular mode gold‐plated copper cavity with the sample and determining the cavity Q for the temperature range 4–300 K. Results indicated that HIP samples which underwent subsequent annealing exhibit, below the critical temperature, a surface resistance approaching an order of magnitude less than copper.
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74.25.N- Response to electromagnetic fields
74.70.-b Superconducting materials other than cuprates
73.25.+i Surface conductivity and carrier phenomena

Study on the stabilization of the high Tc phase in a BiSrCaCuO system

H. G. Lee, C. J. Kim, K. H. Lee, and D. Y. Won

Appl. Phys. Lett. 54, 391 (1989); http://dx.doi.org/10.1063/1.101362 (2 pages) | Cited 10 times

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A high Tc superconductor of Pb‐doped BiSrCaCuO with a Tc of 102 K was prepared. A new phase distinguished from that of undoped BiSrCaCuO was formed by Pb doping. It is reported that the Pb doping, sintering time, and low‐temperature anneal are important to stabilize the high Tc phase in BiSrCaCuO. The Jc value (77 K, H=0) was measured as 23 A/cm2.
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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
74.10.+v Occurrence, potential candidates
81.40.Rs Electrical and magnetic properties related to treatment conditions

Magnetic hardening of Pr‐Fe‐Co‐B alloys by rapid quenching

J. Wecker and L. Schultz

Appl. Phys. Lett. 54, 393 (1989); http://dx.doi.org/10.1063/1.101455 (3 pages) | Cited 12 times

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We have investigated the magnetic properties of liquid‐quenched Pr15 (Fe1−x Cox )77 B8 over the whole range of Co concentrations. The coercivity Hci and the remanence Jr depend on the Co content in the same way as in Nd15 (Fe1−x Cox )77 B8 . For the ternary Pr‐Co‐B a high Hci , as large as 15.2 kA/cm, has been obtained. In Co‐rich alloys the temperature dependence of Hci and Jr is limited by the spin reorientation at temperatures well below the Curie point. Except for Pr15 Co77 B8 , annealing of overquenched ribbons leads to substantially lower coercivities. The possible microstructural origin of the magnetic hardening is discussed.
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75.50.Vv High coercivity materials
81.40.Rs Electrical and magnetic properties related to treatment conditions
75.50.Bb Fe and its alloys

Effects of indium doping on crystalline qualities of GaAs on Si by molecular beam epitaxy

I. Ohbu, M. Ishino, and T. Mozume

Appl. Phys. Lett. 54, 396 (1989); http://dx.doi.org/10.1063/1.100973 (2 pages) | Cited 3 times

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The effects of In doping on crystalline qualities are demonstrated in the heteroepitaxy of GaAs on Si grown by molecular beam epitaxy. The etch pit density of the GaAs layers doped with In at 8×1017 cm−3 decreased by a factor of 7 compared with undoped GaAs layers. Dark regions observed in electron beam induced current images became small by In doping. The improvement of the crystalline qualities was also verified by Raman spectroscopy.
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68.55.-a Thin film structure and morphology
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
78.30.Fs III-V and II-VI semiconductors
FREE

Critique of (time)1/3 kinetics of defect formation in amorphous Si:H and a possible alternative model—Comment on ‘‘Kinetics of the Staebler–Wronski effect in hydrogenated amorphous silicon’’ [Appl. Phys. Lett. 45, 1075 (1984)]

David Redfield

Appl. Phys. Lett. 54, 398 (1989); http://dx.doi.org/10.1063/1.100974 (2 pages) | Cited 8 times

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Abstract Unavailable
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61.72.Bb Theories and models of crystal defects
71.55.Ht Other nonmetals
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping
72.80.Ng Disordered solids
FREE

Response to ‘‘Critique of (time)1/3 kinetics of defect formation in amorphous Si:H and a possible alternative model—Comment on ‘Kinetics of the Staebler–Wronski effect in hydrogenated amorphous silicon’ ’’ [Appl. Phys. Lett. 54, 398 (1989)]

W. B. Jackson, C. C. Tsai, and M. Stutzmann

Appl. Phys. Lett. 54, 399 (1989); http://dx.doi.org/10.1063/1.100975 (2 pages)

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Abstract Unavailable
Show PACS
61.72.Bb Theories and models of crystal defects
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping
72.80.Ng Disordered solids
71.55.Ht Other nonmetals
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