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9 Apr 1990

Volume 56, Issue 15, pp. 1391-1503

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Selective and stoichiometric reaction of copper dipivaloylmethanate [Cu(DPM)2] with surface hydroxyls on SiO2

Rika Sekine and Maki Kawai

Appl. Phys. Lett. 56, 1466 (1990); http://dx.doi.org/10.1063/1.102500 (3 pages) | Cited 14 times

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Stoichiometric reaction of copper dipivaloylmethanate [Cu(DPM)2] with the hydroxyl group (OH) on SiO2 surface was studied by infrared spectroscopy. The stoichiometric ratio of reacted OH and Cu(DPM)2 was estimated to be ∼2–3:1 from the absorbance of the OH and the CH stretching region. The ligand DPM was removed from the SiO2 surface by treatment with water at 400 °C. The oxidation state of Cu remaining on the surface was proven to be +1 by x‐ray photoelectron spectroscopy.
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68.43.-h Chemisorption/physisorption: adsorbates on surfaces
81.15.Kk Vapor phase epitaxy; growth from vapor phase
68.55.-a Thin film structure and morphology
82.30.-b Specific chemical reactions; reaction mechanisms

Fabrication of thin‐film‐type Josephson junctions using a Bi‐Sr‐Ca‐Cu‐O /Bi‐Sr‐Cu‐O/Bi‐Sr‐Ca‐Cu‐O structure

K. Mizuno, K. Higashino, K. Setsune, and K. Wasa

Appl. Phys. Lett. 56, 1469 (1990); http://dx.doi.org/10.1063/1.103173 (3 pages) | Cited 36 times

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Thin‐film Josephson junctions with normal metal barriers using a Bi‐based high Tc oxide superconductor were successfully fabricated. Bi2Sr2Ca1Cu2Ox films were used for both superconducting electrodes and Bi2Sr2Cu1Oy for the barrier layer. The junction area of 20×40 μm2 was defined by photolithography and Ar ion milling. These S/N/S‐type junctions clearly exhibited the ac Josephson effect under the irradiation of radio frequency waves of 12 GHz and more than 20 Shapiro steps were observed.
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85.25.Cp Josephson devices

Characterization of the KrF laser‐induced plasma plume created above a BiSrCaCuO target

C. Girault, D. Damiani, C. Champeaux, P. Marchet, J. P. Mercurio, J. Aubreton, and A. Catherinot

Appl. Phys. Lett. 56, 1472 (1990); http://dx.doi.org/10.1063/1.103155 (3 pages) | Cited 13 times

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The laser‐induced plasma plume created above a BiSrCaCuO superconducting target by a KrF laser beam (248 nm) is investigated by time‐resolved spectroscopy. The influence of the oxygen partial pressure on the ejection velocities of the ablated species and on the relaxation of atomic and molecular excited species is particularly studied.
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81.15.Jj Ion and electron beam-assisted deposition; ion plating
74.78.-w Superconducting films and low-dimensional structures
79.20.Ds Laser-beam impact phenomena

Persistent magnetic fields trapped in high Tc superconductor

R. Weinstein, In‐Gann Chen, J. Liu, D. Parks, V. Selvamanickam, and K. Salama

Appl. Phys. Lett. 56, 1475 (1990); http://dx.doi.org/10.1063/1.103207 (3 pages) | Cited 32 times

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A study of field trapping by the incomplete Meissner effect was performed on YBa2Cu3O7−x at 77 K on both sintered and oriented grain samples. Fields of up to BT=1280 G have been trapped in small, oriented grain, planar samples. Circulating persistent current densities of up to 4800 A/cm2 are calculated. Based on these values hollow cylinders of 2 cm i.d. will trap fields of 6000 G. Initial creep is about 10%/week for both types of samples. Creep rate varies as (BT/BT,max)2. BT, due to an external field B0, is BT∝(1−e−cB0/BT,max). Lamination and mosaic assembly steps for producing practical magnets have been performed.
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74.25.Ha Magnetic properties including vortex structures and related phenomena
74.70.-b Superconducting materials other than cuprates
74.25.Uv Vortex phases (includes vortex lattices, vortex liquids, and vortex glasses)
84.71.Ba Superconducting magnets; magnetic levitation devices

Electrical properties of the interface between YBa2Cu3Ox films and various substrates

Q. Y. Ying and H. S. Kwok

Appl. Phys. Lett. 56, 1478 (1990); http://dx.doi.org/10.1063/1.103208 (3 pages) | Cited 14 times

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The electrical properties of the interfacial layers between YBCO films and various substrates were studied using in situ resistivity measurements. It was found that this method is sensitive to even a 10‐Å‐thick interface layer. Moreover, it yields the resistivity of the interfacial layer and the YBCO film during deposition. For yttria‐stabilized zirconia, the interface has a very low resistivity. For MgO and sapphire the interface has a high resistivity; SrTiO3 falls between these two cases. Sapphire shows a large reaction layer and evidence for nucleated growth, which are probably responsible for its relatively poor superconducting properties.
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74.78.-w Superconducting films and low-dimensional structures
74.70.-b Superconducting materials other than cuprates
73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)

Effect of deposition rate on properties of YBa2Cu3O7−δ superconducting thin films

X. D. Wu, R. E. Muenchausen, S. Foltyn, R. C. Estler, R. C. Dye, C. Flamme, N. S. Nogar, A. R. Garcia, J. Martin, and J. Tesmer

Appl. Phys. Lett. 56, 1481 (1990); http://dx.doi.org/10.1063/1.103209 (3 pages) | Cited 58 times

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Superconducting thin films of YBa2Cu3O7−δ on (100) SrTiO3 are prepared in situ by a pulsed laser deposition technique at deposition rates from 1 to 145 Å/s. Crystallinity of the films is examined by Rutherford backscattering in the channeling mode using a 2.2 MeV He+ ion beam. The backscattering minimum yield (χmin) increases with the deposition rate. A χmin of 3% is observed in the films deposited at the lowest deposition rate. Even at a deposition rate of 145 Å/s, the films show good crystallinity with χmin of 15%, indicating epitaxial growth. The x‐ray diffraction measurements show that the films have strong c‐axis orientation normal to the substrates. The films have metallic resistance versus temperature behavior with zero resistance temperatures of 90 K. The results indicate that the pulsed laser deposition technique could be used to deposit large‐area films efficiently with adequate substrate movement.
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81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
68.55.-a Thin film structure and morphology
74.78.-w Superconducting films and low-dimensional structures
74.70.-b Superconducting materials other than cuprates

Microwave response of YBaCuO thin‐film Dayem bridges

M. A. M. Gijs and R. J. E. Jansen

Appl. Phys. Lett. 56, 1484 (1990); http://dx.doi.org/10.1063/1.103210 (3 pages) | Cited 12 times

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1‐μm‐wide Dayem bridges were patterned with a pulsed Xe laser in c‐axis‐oriented YBaCuO films prepared according to the BaF2 method. The microbridges have a critical current density of 2×106 A/cm2 at 77 K, which is typical for an epitaxial film without grain boundaries. When microwave radiation in the centimeter wavelength range is applied, we observe current steps in the current‐voltage characteristic up to 72 K. The dependence of these steps on microwave power is compared with the model of Golovashkin and Lykov {Zh. Eksp. Teor. Fiz. 74, 214 (1978) [Sov. Phys. JETP 47, 110 (1978)]}; we find that the step amplitude is smaller than predicted.
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74.50.+r Tunneling phenomena; Josephson effects
74.25.N- Response to electromagnetic fields
74.25.Sv Critical currents
74.70.-b Superconducting materials other than cuprates

Anisotropic Josephson junctions of Y‐Ba‐Cu‐O/Au/Nb film sandwiches

H. Akoh, C. Camerlingo, and S. Takada

Appl. Phys. Lett. 56, 1487 (1990); http://dx.doi.org/10.1063/1.103156 (3 pages) | Cited 30 times

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Superconductor‐normal metal‐superconductor (SNS) Josephson junctions consisting of Y‐Ba‐Cu‐O/Au/Nb film‐layered structure have been fabricated using epitaxial Y‐Ba‐Cu‐O films. SNS junctions with a‐b plane orientated Y‐Ba‐Cu‐O films exhibit the Josephson effect, while the junctions with c‐axis orientated Y‐Ba‐Cu‐O films have no Josephson current. Moreover, a‐b plane orientated junctions show anisotropic Fraunhofer patterns in the magnetic field dependence of the critical current according to the direction of film orientations. These anisotropic behaviors reveal that the proximity effect is strongly affected by the anisotropic coherence length and the magnetic penetration depth of Y‐Ba‐Cu‐O films.
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85.25.Cp Josephson devices
74.50.+r Tunneling phenomena; Josephson effects
74.70.-b Superconducting materials other than cuprates
74.78.-w Superconducting films and low-dimensional structures

Strong flux pinning centers in Y‐Ba‐Cu‐O films prepared by chemical vapor deposition

K. Watanabe, T. Matsushita, N. Kobayashi, H. Kawabe, E. Aoyagi, K. Hiraga, H. Yamane, H. Kurosawa, T. Hirai, and Y. Muto

Appl. Phys. Lett. 56, 1490 (1990); http://dx.doi.org/10.1063/1.103211 (3 pages) | Cited 32 times

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The Y‐Ba‐Cu‐O film prepared by chemical vapor deposition showed Tc=91.5 K and Bc2 (77.3 K)=60 T defined by zero resistance. The Jc values measured at 77.3 K were 7.8×105 A/cm2 at B=0 and 1.0×105 A/cm2 at 16 T, magnetic fields perpendicular to the c axis. Small disk‐shaped precipitates possibly regarded as strong flux pinning centers in the Y‐Ba‐Cu‐O films were observed using transmission electron microscopy. The evaluation of Jc related to the concentration and configuration of the precipitates was in reasonable agreement with the measured Jc values.
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74.25.Uv Vortex phases (includes vortex lattices, vortex liquids, and vortex glasses)
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
74.25.Sv Critical currents

Noise and dc characteristics of thin‐film Bi‐Sr‐Ca‐Cu‐oxide dc SQUIDs

D. W. Face, J. M. Graybeal, T. P. Orlando, and D. A. Rudman

Appl. Phys. Lett. 56, 1493 (1990); http://dx.doi.org/10.1063/1.103157 (3 pages) | Cited 8 times

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Highly oriented Bi‐Sr‐Ca‐Cu‐oxide thin films with Tc≥100 K and large (10–20 μm) grains were used to produce thin‐film dc superconducting quantum interference devices (SQUIDs). The best SQUID, which operated up to 75 K, had an inside loop diameter of ∼18 μm and an estimated loop inductance of 30 pH. The device was patterned by standard photolithography and had weak links that were likely due to existing grain boundaries around the loop. The effective loop area, calculated from the period of the SQUID modulation, is roughly consistent with the geometrical area of the SQUID loop. Significant hysteresis was observed in the flux‐voltage characteristic which depended on the amplitude of the magnetic field sweep. The 1/f noise levels measured at 100 Hz in this device gave a flux noise Sϕ of 1.0×10−8 Φ20/Hz at 4.8 K and 2.3×10−7 Φ20/Hz at 60 K. The detailed noise measurements which we report for this SQUID are the first for any Bi‐Sr‐Ca‐Cu‐oxide based SQUID.
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85.25.Dq Superconducting quantum interference devices (SQUIDs)
74.70.-b Superconducting materials other than cuprates
74.40.-n Fluctuation phenomena

Sputtered BiPbSrCaCuO films on polycrystalline CuO substrates

S. K. Das, R. Suryanarayanan, and O. Gorochov

Appl. Phys. Lett. 56, 1496 (1990); http://dx.doi.org/10.1063/1.103212 (2 pages) | Cited 2 times

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BiPbSrCaCuO films have been deposited for the first time onto polycrystalline CuO substrates by dc sputtering. The films become superconducting after they are post‐annealed in air. Zero resistivity is observed between 38 and 72 K depending on the annealing conditions. The sample showing an onset at 105 K gives an extrapolated zero resistivity at 90 K. The preparation and annealing conditions are described.
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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

Electronic transitions in a SimGen strained monolayer superlattice measured by photoreflectance

P. A. Dafesh, V. Arbet, and K. L. Wang

Appl. Phys. Lett. 56, 1498 (1990); http://dx.doi.org/10.1063/1.103158 (3 pages) | Cited 6 times

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The first photoreflectance spectrum from a short‐period strain‐symmetrized SimGen superlattice has been measured at 87 K. Fifteen electronic transitions were measured between 1.1 and 2.7 eV and fit well to a third derivative functional form. Most of the transition energies were calculated using a one‐band envelope‐function model, adding strain and spin orbit shifts as first‐order corrections. Additional transitions were observed near the expected interband energies in an unstrained Si0.2Ge0.8 random alloy. All of the calculated transition energies were found to agree to within 80 meV of the measured values.
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73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
73.61.Cw Elemental semiconductors
73.61.Jc Amorphous semiconductors; glasses
73.61.Le Other inorganic semiconductors
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
78.66.-w Optical properties of specific thin films

Dynamic optoelectronic read/write memory

R. N. Nottenburg, A. F. J. Levi, T. Tanbun‐Ek, and R. A. Logan

Appl. Phys. Lett. 56, 1501 (1990); http://dx.doi.org/10.1063/1.103159 (3 pages)

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We have used multielectrode laser diodes to demonstrate a dynamic digital optoelectronic memory with read and write capability. Pulses 5 ns wide are recirculated in the system every 50 ns. Bits may be modified by applying positive or negative voltage control pulses to an intracavity absorber in the device.
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85.60.-q Optoelectronic devices
85.60.Dw Photodiodes; phototransistors; photoresistors
42.79.Vb Optical storage systems, optical disks
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