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13 May 2002

Volume 80, Issue 19, pp. 3467-3650

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In situ growth of superconducting MgB2 thin films with preferential orientation by molecular-beam epitaxy

W. Jo, J-U. Huh, T. Ohnishi, A. F. Marshall, M. R. Beasley, and R. H. Hammond

Appl. Phys. Lett. 80, 3563 (2002); http://dx.doi.org/10.1063/1.1478151 (3 pages) | Cited 66 times

Online Publication Date: 7 May 2002

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We report the synthesis of superconducting MgB2 thin films grown in situ by molecular-beam epitaxy. Mg-rich fluxes are deposited with B flux by electron-beam evaporation onto c-plane sapphire substrates. The films exhibit c-axis oriented peaks of MgB2, and a full width at half maximum of 3° in their rocking curves. In-plane alignment of MgB2 shows 12-fold symmetry, which is observed by the selected area diffraction pattern in transmission electron microscopy. The MgB2 films show a superconducting transition at 34.5 K with ΔTc<1 K. Even though the residual resistivity of the films is quite high (∼60 μΩ cm), the normal-state resistivity has a very similar temperature dependence but is five times larger than that of a single crystal, implying that conduction through the whole sample is imperfectly connected or inhomogeneous. Upper critical fields are obtained from measurement of the field dependence of the resistivity. It is estimated that the upper critical field at 20 K is more than 15 T, which is one of the largest values ever reported. © 2002 American Institute of Physics.
Show PACS
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
68.55.A- Nucleation and growth
74.72.-h Cuprate superconductors
74.78.-w Superconducting films and low-dimensional structures
68.55.-a Thin film structure and morphology
81.40.Ef Cold working, work hardening; annealing, post-deformation annealing, quenching, tempering recovery, and crystallization
68.37.Lp Transmission electron microscopy (TEM)
74.25.Op Mixed states, critical fields, and surface sheaths
74.25.F- Transport properties
74.10.+v Occurrence, potential candidates
74.62.Bf Effects of material synthesis, crystal structure, and chemical composition

Strong reduction of thermally activated flux jump rate in superconducting thin films by nanodot-induced pinning centers

A. Crisan, P. Badica, S. Fujiwara, J. C. Nie, A. Sundaresan, Y. Tanaka, and H. Ihara

Appl. Phys. Lett. 80, 3566 (2002); http://dx.doi.org/10.1063/1.1478782 (3 pages) | Cited 15 times

Online Publication Date: 7 May 2002

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From frequency-dependent ac susceptibility studies of (Cu,T1)BaSrCa2Cu3Oy superconducting thin films, with and without nanodot-induced artificial pinning centers, we estimated the activation energy of flux jumps. The result was that, in the film with nanodots, the pinning potential is several times higher, leading to a probability of thermally activated flux jumps several orders of magnitude lower than in the film without artificial pinning centers. We suggest that our no cost straightforward method for creating extended defects can be successfully employed for the reduction of thermal noise in superconducting electronic devices. © 2002 American Institute of Physics.
Show PACS
74.72.-h Cuprate superconductors
74.78.-w Superconducting films and low-dimensional structures
74.25.Uv Vortex phases (includes vortex lattices, vortex liquids, and vortex glasses)
61.72.Nn Stacking faults and other planar or extended defects
74.25.Ha Magnetic properties including vortex structures and related phenomena
68.65.Hb Quantum dots (patterned in quantum wells)

Properties of superconducting MgB2 single crystal grown by a modified flux method

Yong Chan Cho, Sang Eon Park, Se-Young Jeong, Chae-Ryong Cho, Bong Jun Kim, Young Cheol Kim, and Hwa Shik Youn

Appl. Phys. Lett. 80, 3569 (2002); http://dx.doi.org/10.1063/1.1479198 (3 pages) | Cited 2 times

Online Publication Date: 7 May 2002

Full Text: Read Online (HTML) | Download PDF

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We report on the growth of MgB2 single crystals with a large thickness of about 100 μm and a clear hexagonal prismatic morphology. On the low-field magnetization curve M(T), a superconducting transition was observed at 39 K. Using the x-ray diffractometer equipped with a microprobe, we obtained Laue patterns of MgB2 single crystal from a piece of the grown crystal and investigated the impurities introduced during the growing process using Auger electron spectroscopy. © 2002 American Institute of Physics.
Show PACS
74.72.-h Cuprate superconductors
74.62.Bf Effects of material synthesis, crystal structure, and chemical composition
74.25.Ha Magnetic properties including vortex structures and related phenomena
81.10.Fq Growth from melts; zone melting and refining
74.10.+v Occurrence, potential candidates
79.20.Fv Electron impact: Auger emission
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