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6 Apr 1998

Volume 72, Issue 14, pp. 1667-1789

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A probe for the investigation of the superconducting metastable state in YBa2Cu3O7−x step-edge junctions

S. Barbanera, M. G. Castellano, G. Torrioli, and M. Cirillo

Appl. Phys. Lett. 72, 1760 (1998); http://dx.doi.org/10.1063/1.121176 (3 pages) | Cited 3 times

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We have investigated the pair tunneling process in YBa2Cu3O7−x step-edge Josephson junctions by studying the lifetime of the metastable zero-voltage state determined by the thermal activation out of the potential well. The junctions have a hysteretic current–voltage characteristic at 4.2 K, which allows the recording of transitions and switching distribution from the Josephson current to the resistive state. By applying an external magnetic field, we have found a strong dependence of the activation energy on the field intensity. Striking similarities with analogous measurements performed on low Tc conventional tunnel junctions suggest that the high Tc counterparts can be described by a standard model for long junctions. © 1998 American Institute of Physics.
Show PACS
74.72.-h Cuprate superconductors
74.50.+r Tunneling phenomena; Josephson effects
74.40.-n Fluctuation phenomena
74.78.Fk Multilayers, superlattices, heterostructures
74.20.Fg BCS theory and its development

Superconducting YBa2Cu3O7−x thin films on polycrystalline ferrite for magnetically tunable microwave components

Q. X. Jia, A. T. Findikoglu, P. Arendt, S. R. Foltyn, J. M. Roper, J. R. Groves, J. Y. Coulter, Y. Q. Li, and G. F. Dionne

Appl. Phys. Lett. 72, 1763 (1998); http://dx.doi.org/10.1063/1.121177 (3 pages) | Cited 11 times

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Superconducting YBa2Cu3O7−x (YBCO) thin films with a surface resistance of 0.86 mΩ at 10 GHz and 76 K have been grown on polycrystalline ferrite yttrium iron garnet (YIG) substrates. The chemical and structural mismatches between YBCO and YIG are solved by using a double buffer layer of biaxially oriented yttria-stabilized zirconia (YSZ) and CeO2, where YSZ is deposited by an ion-beam-assisted-deposition technique. The YBCO films are c axis oriented with an in-plane mosaic spread [full width at half maximum of an x-ray ϕ-scan on (103) reflection] of less than 8°. The films have a superconductive transition temperature above 88 K with a transition width less than 0.3 K, giving a critical current density above 106 A/cm2 in self field at 75 K. At 75 K in an external magnetic field of 1 T perpendicular to the film surface, the films maintain a critical current density over 2×105 A/cm2. © 1998 American Institute of Physics.
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74.72.-h Cuprate superconductors
74.78.-w Superconducting films and low-dimensional structures
74.62.Bf Effects of material synthesis, crystal structure, and chemical composition
85.25.-j Superconducting devices

Minimization of detrimental effect of air in HgBa2CaCu2O6+δ thin film processing

B. W. Kang, A. A. Gapud, X. Fei, T. Aytug, and J. Z. Wu

Appl. Phys. Lett. 72, 1766 (1998); http://dx.doi.org/10.1063/1.121178 (3 pages) | Cited 1 time

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We have studied the effects of halogenizing HgBa2CaCu2O6+δ (Hg-1212) thin films and have found that the addition of chlorine/fluorine significantly enhances (1) the reproducibility and stability of Hg-1212 thin films, (2) the phase purity of Hg-1212 to over 90%, and (3) the magnetic critical current density (Jc,mag) both at zero field and in-field. A possible mechanism of preventing contamination of precursor materials by chlorine/fluorine doping is proposed. © 1998 American Institute of Physics.
Show PACS
81.15.Cd Deposition by sputtering
74.25.Sv Critical currents
74.78.-w Superconducting films and low-dimensional structures
74.72.-h Cuprate superconductors

Proximity effect in bilayer films of YBa2Cu2.7Fe0.3Oy and YBa2Cu3O7−δ

O. Nesher, G. Koren, E. Polturak, and G. Deutscher

Appl. Phys. Lett. 72, 1769 (1998); http://dx.doi.org/10.1063/1.121179 (3 pages) | Cited 4 times

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We studied the proximity effect in a series of YBa2Cu2.7Fe0.3Oy/YBa2Cu3O7−δ bilayer film with varying YBa2Cu3O7−δ thickness. In a bilayer of isolated YBCO islands, a Tc of 72 K was observed, much higher than Tc of 32 K of the YBa2Cu2.7Fe0.3Oy film. Tc and Jc of thicker bilayers of continuous YBa2Cu3O7−δ films were found to decrease with decreasing YBCO thickness. This behavior of Tc and Jc can be explained by the Deutscher de Gennes theory for the proximity effect, provided one models the film as a series of grains whose lateral dimensions scale with the average film thickness. © 1998 American Institute of Physics.
Show PACS
74.78.-w Superconducting films and low-dimensional structures
74.50.+r Tunneling phenomena; Josephson effects
74.25.Sv Critical currents
74.72.-h Cuprate superconductors
74.10.+v Occurrence, potential candidates

Nonlinear I–V characteristics and proximity effects for PrBa2Cu3O7−δ/YBa2Cu3O7−δ bilayered structures grown on (001) YBa2Cu3O7−δ single crystal substrates

Toshiyuki Usagawa, Yoshihiro Ishimaru, Jianguo Wen, Tadashi Utagawa, Satoshi Koyama, and Youichi Enomoto

Appl. Phys. Lett. 72, 1772 (1998); http://dx.doi.org/10.1063/1.121180 (3 pages) | Cited 8 times

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We have observed superconductivity induced by proximity effects for 100 nm thick (001) PrBa2Cu3O7−δ films pseudomorphically grown on (001) YBa2Cu3O7−δ single crystal substrates by vertical four-probe measurements. The induced superconductivity disappeared around 28 K and was recovered at around 15 K. The 220 nm thick (001) PrBa2Cu3O7−δ/YBa2Cu3O7−δ bilayers show nonlinear I–V behavior with 0.2 mV built-in potential at low temperature below 50 K. The local maximum of the vertical resistance appears around 25 K. © 1998 American Institute of Physics.
Show PACS
74.50.+r Tunneling phenomena; Josephson effects
74.78.-w Superconducting films and low-dimensional structures
74.78.Fk Multilayers, superlattices, heterostructures
74.72.-h Cuprate superconductors
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