High-quality MgB2 films on boron crystals with onset Tc of 41.7 K

Abstract

The simple binary compound, MgB2, has created enormous excitement, due to its remarkably high Tc (39 K), its exotic electronic and phononic structure, as well as its potential technological application. However, contrary to the initial expectation, worldwide efforts to enhance the Tc of this material by means of chemical doping and applying hydrostatic pressure have failed. Investigations of other diborides or related materials have also resulted in finding of lower Tc’s. In this letter we report a slight, but significant enhancement of Tc in MgB2 films grown on boron crystals, which may stem from tensile-type strain. This finding opens up a new possibility for further optimizing Tc in MgB2 and perhaps in related materials.