Growth of magnesium diboride films on 2 inch diameter copper discs by hybrid physical–chemical vapor deposition.

Magnesium diboride (MgB2) coating is a potential candidate to replace bulk niobium (Nb) for superconducting radio frequency cavities due to the appealing superconducting properties of MgB2. MgB2 coating on copper may allow cavity operation near 20–25 K as a result of the high transition temperature (Tc) of MgB2 and excellent thermal conductivity of Cu. We have grown MgB2 films on 2 inch diameter Cu discs by hybrid physical–chemical vapor deposition for radio frequency characterization. Structural and elemental analyses showed a uniform MgB2 coating on top of a Mg–Cu alloy layer with occasional intrusion of Mg–Cu alloy regions. High Tc values of around 37 K and high critical current density (Jc) on the order of 107 A cm−2 at zero field were observed. Radio frequency measurements at 11.4 GHz confirmed a high Tc and showed a quality factor (Q0) much higher than for Cu and close to that of Nb. [ABSTRACT FROM AUTHOR]