MgB2thin films have superior superconducting properties compared to bulk MgB2and demonstrate the potential for further improving the performances of MgB2wires and tapes.Using transmission electron microscopy, we have characterized the microstructure of pure and C-doped MgB2using various carbon sources grown by hybrid physical-chemical vapor deposition (HPCVD), and cold-grown-annealed film deposited by molecular beam epitaxy (MBE). The MgB2HPCVD films increase in crystal quality in the order (MeCp)2Mg-sourced films, CH4-sourced films, B(CH3)3-sourced films, pure films, while the Hc2values of these films follow the opposite order. The cold-grown-annealed MgB2MBE film contains non-epitaxial ≤10 nm MgB2grains 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.
- Ceramics and Composites
- Condensed Matter Physics
- Metals and Alloys
- Electrical and Electronic Engineering
- Materials Chemistry