Epitaxial Ultrathin MgB2 Films on C-Terminated 6H–SiC ($000\bar{1}$) Substrates Grown by HPCVD

Smooth and uniform epitaxial ultrathin MgB
₂
films are desired for various electronic applications including hot-electron bolometers and single-photon detectors. However, the growth of ultrathin MgB
₂
films on SiC substrates using the Hybrid Physical-Chemical Vapor Deposition was dominated by the Volmer-Weber or island growth mode, which limited the minimum thickness for a conductive MgB
₂
film. Here we show the results of a study on the very early stage of the MgB
₂
film growth. We find that the root-mean-squared roughness and grain connectivity of ultrathin MgB
₂
films grown on C-terminated 6H-SiC(
$000\bar{1}$
) substrate is much better than those on Si-terminated substrate. The result provides a simple solution to growing high-quality ultrathin MgB
₂
films for applications.