High Upper Critical Field and Critical Current Density of Carbon-doped MgB$_{2}$ Films by HPCVD Using TMB

Carbon-doping is effective to enhance upper critical field $H_{c2}$ and critical current density $J_{c}$ of MgB$_{2}$. Using Trimethylboron (TMB) as the doping source, we have successfully fabricated carbon-doped MgB$_{2}$ thin films by the Hybrid Physical-Chemical Vapor Deposition (HPCVD) method. Large temperature derivative $-dH_{c2}^{//ab} /dT$ values near $T_{c}$, as high as 8.3 T/K, have been achieved for heavily doped samples. These values are much higher than what have been reported before. With $T_{c}$ over 30 K, $H_{c2}^{//ab} (0)$ values over 100 T can be expected for these samples. For lightly doped films, $J_{c}$ values, larger than 10$^{5}$ A/cm$^{2}$ at 5 K under 9 T perpendicular field and 10$^{4}$ A/cm$^{2}$ at 20 K under 5 T perpendicular field, were obtained. The results demonstrate that carbon-doped MgB$_{2}$ films by HPCVD using TMB are promising for high field applications.