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$_2$ phase thermodynamically stable can be achieved for the {\it in situ} growth of MgB$_2$ thin films. The films grow epitaxially on (0001) sapphire and (0001) 4H-SiC substrates and show a bulk-like $T_c$ of 39 K, a $J_c$(4.2K) of $1.2 \times 10^7$ A/cm$^2$ in zero field, and a $H_{c2}(0)$ of 29.2 T in parallel magnetic field. The surface is smooth with a root-mean-square roughness of 2.5 nm for MgB$_2$ films on SiC. This deposition method opens tremendous opportunities for superconducting electronics using MgB$_2$

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 pressure–temperature phase diagram, in which the magnesium pressure is very high for likely in situ growth temperatures. A Hybrid Physical–Chemical 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 B₁₂As₂

Palladium, Pt, and Cr/Pt contacts to the wide band gap icosahedral boride semiconductor B₁₂As₂ 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 6Ω cm² as-deposited to 3x10[superscript]-⁴ Ω cm² 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