MgB2 thin films have superior superconducting properties compared to bulk MgB2 and demonstrate the potential for further improving the performances of MgB2 wires and tapes.Using transmission electron microscopy, we have characterized the microstructure of pure and C-doped MgB2 using various carbon sources grown by hybrid physical-chemical vapor deposition (HPCVD), and cold-grown-annealed film deposited by molecular beam epitaxy (MBE). The MgB2 HPCVD films increase in crystal quality in the order (MeCp)2Mg-sourced films, CH4-sourced films, B(CH3)3-sourced films, pure films, while the Hc2 values of these films follow the opposite order. The cold-grown-annealed MgB2 MBE film contains non-epitaxial ≤10 nm MgB2 grains and MgO nanoparticles. The microstructural origins of electron scattering and flux pinning in both films are discussed. We also show the structure and chemistry of the degraded phase in HPCVD films and its effects on superconducting properties.
All Science Journal Classification (ASJC) codes
- Ceramics and Composites
- Condensed Matter Physics
- Metals and Alloys
- Electrical and Electronic Engineering
- Materials Chemistry