6 research outputs found
In situ epitaxial MgB2 thin films for superconducting electronics
A thin film technology compatible with multilayer device fabrication is
critical for exploring the potential of the 39-K superconductor magnesium
diboride for superconducting electronics. Using a Hybrid Physical-Chemical
Vapor Deposition (HPCVD) process, it is shown that the high Mg vapor pressure
necessary to keep the MgB phase thermodynamically stable can be achieved
for the {\it in situ} growth of MgB thin films. The films grow epitaxially
on (0001) sapphire and (0001) 4H-SiC substrates and show a bulk-like of
39 K, a (4.2K) of A/cm in zero field, and a
of 29.2 T in parallel magnetic field. The surface is smooth with a
root-mean-square roughness of 2.5 nm for MgB films on SiC. This deposition
method opens tremendous opportunities for superconducting electronics using
MgB
Deposition and Properties of Superconducting MgB 2 Thin Films
The recently discovered superconductor MgB 2 with T c at 39 K has great potential in superconducting electronics. In this paper, we review the deposition techniques used for MgB 2 thin films in the light of a thermodynamic study of the Mg-B system with the calculation of phase diagrams (CALPHAD) modeling technique. This thermodynamic study identifies a growth window in the pressureâtemperature phase diagram, in which the magnesium pressure is very high for likely in situ growth temperatures. A Hybrid PhysicalâChemical Vapor Deposition (HPCVD) technique that successfully achieves such a high Mg pressure is shown to produce in situ epitaxial MgB 2 thin films with bulk superconducting properties.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/45120/1/10948_2004_Article_474022.pd
Cr/Pt Ohmic contacts to BââAsâ
Palladium, Pt, and Cr/Pt contacts to the wide band gap icosahedral boride semiconductor BââAsâ have been studied. All Pd and Pt contacts exhibited nonlinear I-V characteristics, while Cr/Pt contacts were Ohmic. The specific contact resistance was reduced from 6⊠cmÂČ as-deposited to 3x10[superscript]-⎠⊠cmÂČ after the Cr/Pt contacts were annealed at 750 °C for 30 s in Ar. Annealing at 600 °C or higher drastically reduced the semiconductor sheet resistance, whether annealing was performed before or after metallization. This apparent activation of the semiconductor is a likely cause for the improvement in the Ohmic contacts with annealing