Progress in the deposition of MgB₂ thin films

An MgB₂ thin film deposition technology is the first critical step in the development of superconducting electronics utilizing the 39 K superconductor. It turned out to be a challenging task due to the volatility of Mg and phase stability of MgB₂, the low sticking coefficients of Mg at elevated temperatures, and the reactivity of Mg with oxygen. A brief overview of current deposition techniques is provided here from a thermodynamic perspective, with an emphasis on a very successful technique for high quality in situ epitaxial MgB₂ films, the hybrid physical-chemical vapour deposition. Examples of heterostructures of MgB₂ with other materials are also presented.