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15 Aug 1988

Volume 53, Issue 7, pp. 541-627

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Annealing studies of YBa2Cu3O7−x thin films

S. I. Shah

Appl. Phys. Lett. 53, 612 (1988); http://dx.doi.org/10.1063/1.100635 (3 pages) | Cited 6 times

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In situ electrical resistance measurements, differential thermal analysis, and x‐ray diffraction studies were carried out between room temperature and 950 °C on as‐grown amorphous insulating YBa2Cu3O7−x thin films. Results for the phase transformation reaction path are reported in order to optimize the post‐deposition annealing process. Amorphous‐to‐crystalline transformations were observed at 550 °C along with a reversible orthorhombic‐tetragonal transition near 670 °C. Eutectic melting above 850 °C was also noted, which restricts the maximum annealing temperature to around 850 °C.
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74.78.-w Superconducting films and low-dimensional structures
68.55.Nq Composition and phase identification
81.40.Rs Electrical and magnetic properties related to treatment conditions
74.70.-b Superconducting materials other than cuprates

Further evidence for the presence of c=38.2 Å phase in a Bi‐Ca‐Sr‐Cu‐O superconductor

R. Ramesh, C. J. D. Hetherington, G. Thomas, S. M. Green, C. Jiang, M. L. Rudee, and H. L. Luo

Appl. Phys. Lett. 53, 615 (1988); http://dx.doi.org/10.1063/1.99869 (3 pages) | Cited 11 times

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Results of high‐resolution electron microscopy, convergent beam electron microscopy, and x‐ray microanalysis on the high Tc phase are reported. Local inhomogeneities in the structure and composition have been observed along the c direction. Both c=30.56 Å (8ap) and c=38.2 Å (10ap) have been observed inside the same grain. The regions with the larger c parameter correspond to regions with higher Ca and Cu concentration suggesting that the range of transition temperatures observed (85 to 115 K) is due to the coexistence of such regions of c=38.2 Å and c=30.56 Å.
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74.70.-b Superconducting materials other than cuprates
61.66.Fn Inorganic compounds
64.70.K- Solid-solid transitions

Plasma oxidation of Ba2YCu3O7−y thin films

H. Tamura, A. Yoshida, S. Morohashi, and S. Hasuo

Appl. Phys. Lett. 53, 618 (1988); http://dx.doi.org/10.1063/1.100636 (3 pages) | Cited 6 times

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We studied the effects of plasma oxidation on the electrical properties of Ba2YCu3O7−y thin films. Films were prepared by electron beam evaporation, then annealed in oxygen. Plasma oxidation, performed in a barrel reactor, lowered the room‐temperature resistivity of films and raised the zero‐resistance temperature. Film resistivity increased a few percent a day after plasma oxidation. The rate of resistivity increase is several times that of untreated samples. Changes in resistivity and critical temperature could be completely reversed by repeated plasma treatment.
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81.05.Je Ceramics and refractories (including borides, carbides, hydrides, nitrides, oxides, and silicides)
81.65.-b Surface treatments
74.78.-w Superconducting films and low-dimensional structures
74.70.-b Superconducting materials other than cuprates
81.40.Rs Electrical and magnetic properties related to treatment conditions

Telegraph‐like noise in Y‐Ba‐Cu oxide thin‐film dc SQUID’s

M. Matsuda and S. Kuriki

Appl. Phys. Lett. 53, 621 (1988); http://dx.doi.org/10.1063/1.100637 (3 pages) | Cited 11 times

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We have observed a telegraph‐like noise in dc superconducting quantum interference devices (SQUID’s) made of low‐temperature synthesized superconducting Y‐Ba‐Cu oxide thin films. The voltage of the SQUID jumps among two to four discrete levels randomly with time, and exhibits a Lorentzian type frequency dependence in the power spectrum. Periodic modulations of the voltage with magnetic flux are observed in a SQUID having narrow bridges of submicrometer width. The flux noise of the SQUID is dominated by the telegraph‐like noise at low frequencies.
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85.25.Dq Superconducting quantum interference devices (SQUIDs)
74.78.-w Superconducting films and low-dimensional structures
74.70.-b Superconducting materials other than cuprates
74.40.-n Fluctuation phenomena

Vacuum deposition of multilayer Bi‐Ca‐Sr‐Cu‐O superconducting thin films

V. Paserin, M. A. Rashti, and D. E. Brodie

Appl. Phys. Lett. 53, 624 (1988); http://dx.doi.org/10.1063/1.100638 (2 pages) | Cited 5 times

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Superconducting Bi‐Ca‐Sr‐Cu‐O thin films were prepared by sequential evaporation of layers of Cu, Ca, Bi2O3, and Sr on single‐crystal MgO substrates, followed by an anneal in an O2 atmosphere. An electron beam source was used for Sr and resistively heated sources for Cu, Ca, and Bi2O3. An onset transition temperature of around 80 K was observed with a resistance anomaly at 105 K. The film properties were found to be very sensitive to the anneal conditions. Samples were characterized by resistivity measurements, Auger spectroscopy, scanning electron microscopy, and energy dispersive x‐ray microanalysis.
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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
68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties
81.40.Rs Electrical and magnetic properties related to treatment conditions

Field‐stimulated exoelectron emission from 99.9999% pure Al

M. Tagawa, S. Takenobu, N. Ohmae, and M. Umeno

Appl. Phys. Lett. 53, 626 (1988); http://dx.doi.org/10.1063/1.99835 (2 pages) | Cited 9 times

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Exoelectrons were emitted from a 99.9999% pure Al tip by applying an electric field as a stimulus. This occurred at lower voltages than that necessary for field emission of electrons. Field‐stimulated exoelectron emission showed a characteristic storage effect in accordance with the time interval of applied voltage pulses. Based upon this storage effect and a computer calculation of the field strength at the apex of the tip, we show by analytical discussions that exoelectrons are emitted by tunneling, not by the Schottky effect.
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79.75.+g Exoelectron emission
78.30.Er Solid metals and alloys
78.40.Kc Metals, semimetals, and alloys
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