Carbon-doped MgB sub(2) thin films grown by hybrid physical-chemical vapor deposition

• Published in: IEEE transactions on applied superconductivity 2005-01, Vol.15 (2)
• Main Authors: Pogrebnyakov, A V, Redwing, J M, Giencke, JE, Eom, C B, Vaithyanathan, V, Schlom, D G, Soukiassian, A, Mi, S B, Jia, CL, Chen, J, Hu, Y F, Cui, Y, Li, Qi, Xi, X X
• Format: Article
• Language: English
• Subjects: Borides; Carbon; Electrical resistivity; Grain boundaries; Magnesium; Magnesium compounds; Nanostructure; Thin films; Vapor deposition
• ISSN: 1051-8223
• DOI: 10.1109/TASC.2005.848871

Carbon-doped MgB sub(2) thin films have been produced with hybrid physical-chemical vapor deposition (HPCVD) by adding a carbon-containing metalorganic magnesium precursor, bis(methylcyclopentadienyl)magnesium, to the carrier gas. The amount of the carbon added, thus the carbon content in the films, was controlled by the flow rate of a secondary hydrogen gas flow through the precursor bubbler. X-ray diffraction and electron microscopy showed that the carbon-doped MgB sub(2) films are textured with c-axis oriented columnar nano-grains and highly resistive amorphous areas at the grain boundaries. When the amount of carbon in the films increases, the resistivity increases dramatically while T sub(c) decreases much more slowly as the current-carrying cross section is reduced by the grain boundaries. The temperature-dependent part of the resistivity, Delta rho identical with rho (300 K)- rho (50 K), increases only modestly until the highly resistive grain boundaries completely cut off the conducting path. The impact of the reduced cross section on critical current density J sub(c) is discussed.