Aluminum Ion Implantation in MgB2 Thin Films

Superconducting magnesium diboride is a possible candidate for replacing Nb in superconducting radio frequency (SRF) cavities because of its higher T
_c
and potentially higher breakdown field. However, the existence of two energy gaps, the σ gap at 7.2 eV and the π gap at 2.2 eV, could impact the RF properties of MgB
₂
. It has been shown that chemical doping and disorder can increase the interband scattering, thus modifying the two gaps. In this work, we performed Al ion implantation in MgB
₂
thin films to introduce Al doping in the films. The Al ion implanted films showed decreases in transition temperature, from 40.4 K in the pristine films to non-superconducting above the dose of 2 × 10
¹⁴
atoms/cm
²
. An expansion in the c-axis lattice parameter with increasing dose was also observed. These results suggest that the degradation of superconductivity in the Al ion implanted films is mainly due to the ion beam damage rather than Al doping.