A simple method for the enhancement of Jc in MgB2 thick films with an amorphous SiC impurity layer
We investigated the effect of SiC doping on the critical current density (Jc) in MgB2 thick films using amorphous SiC impurity layers of various thicknesses: 7, 14, 35, and 70 nm. SiC impurity layers were first deposited on the Al2O3(0001) substrates at room temperature by using a pulsed laser deposition system, after which MgB2 films were grown on the SiC deposited precursor substrates by using a hybrid physical–chemical vapor deposition technique at a low growth temperature of 480 °C. All samples showed a high transition temperature of ~40 K irrespective of the thickness of the impurity layer. The grain sizes of the MgB2 films slightly increased from 400 to 488 nm with increasing thickness of the impurity layer. The MgB2 thick film with a 35 nm thick SiC impurity layer exhibited the highest Jc, while all SiC doped samples showed a higher Jc than a pure MgB2 thick film throughout the whole magnetic field region. These results suggest that the SiC particles of the impurity layer diffused into the MgB2 films during film growth, and the SiC particles, along with the columnar grain boundaries in the MgB2 thick films, act as strong pinning centers.