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Magnesium diboride (MgB₂) is a promising superconducting material, with a critical temperature T_c of 39 K – the highest among conventional superconductors at ambient pressure. This high T_c allows MgB₂ based superconducting electronics, such as Josephson junctions and superconducting quantum interference devices (SQUID), to operate at relatively higher temperatures (≥ 20 K) and higher speeds. MgB₂ has a hexagonal layered crystal structure and is readily coupled with many other layered hexagonal materials, such as graphene, transition-metal dichalcogenides, and many topological insulators, to build novel devices for information sensing and processing.

To create epitaxial MgB₂ films suitable for mass production, molecular beam epitaxy (MBE) is the most proper growth technique. It can enable one step growth of epitaxial MgB₂ films at relatively low substrate temperature (150–320 °C, suitable for multilayer growth and subsequent device integration). However, even within such a narrow temperature window, the ability to control the film quality is a delicate process. With help of in situ reflection high-energy electron diffraction (RHEED) patterns, the research group at University of Waterloo led by Prof. Guo-Xing Miao recently found a way to grow high quality MgB₂ films on whole Si wafers by adopting a self-limiting growth process. The team also fabricated micro-sized MgB₂/MgO/MgB₂ Josephson junctions. Transport measurements on these junctions exhibit very good I-V characteristics. Field modulations of the I–V curves show clear Fraunhofer patterns and Fiske steps, further confirming extremely good quality of the materials . These achievements pave the way for large-scale deployment of MgB₂ thin film devices.