MgB2 thin films

Great progress has been made in the deposition of MgB2 thin films since the discovery of superconductivity at 39 K in this two-band superconductor. In this review, deposition techniques used for MgB2 are described, with an emphasis on their meeting the critical requirements for growing high-quality MgB2 thin films. The availability of these thin films has contributed significantly to the research on the two-gap superconductivity in MgB2. MgB2 thin films have also been investigated for applications in high-field magnets, superconducting electronic devices and circuits, and radio-frequency cavities used in accelerators. (topical review)