Influence of Mg deficiency on superconductivity in MgB2 thin films grown by HPCVD
Abstract:The effects of Mg deficiency in MgB2 films grown by hybrid physical–chemical vapor deposition were investigated after vacuum annealing at various temperatures. High-quality MgB2 films grown on c-cut Al2O3 substrates with different superconducting transition temperatures (Tcs) of 40.2 and 41 K were used in this study. As the annealing temperature was increased from 200 to 800 °C, the Mg content in the MgB2 films systemically decreased, but the Tcs did not change, within ± 0.12 K, until the annealing temperature reached 700 °C. For MgB2 films annealed at 800 °C for 30 min, however, no superconductivity was observed, and the temperature dependence of the resistivity showed a semiconducting behavior. We also found that the residual resistivity ratio decreased with increasing annealing temperature.
Document Type: Research Article
Publication date: December 1, 2007