Prospects and problems in fabrication of MgB₂ Josephson junctions

We briefly survey recent developments in the thin film synthesis and junction fabrication of MgB₂ toward superconducting electronics. The most serious problem in the thin film synthesis of MgB₂ is the high vapor pressure required for phase stability. This problem makes insitu film growth difficult. However, there has been substantial progress in thin film technology for MgB₂ in the past three years. The low-temperature thin-film process in a UHV chamber can produce high-quality MgB₂ films with T_c ∼ 35 K. Furthermore, technology to produce single-crystal epitaxial MgB₂ films has recently been developed by using hybrid physicalchemical vapor deposition. With regard to Josephson junctions, various types of junctions have been fabricated, all of which indicate that MgB₂ has potential for superconducting devices that operate at 20-30 K, the temperature reached by current commercial crvocoolers.