Fast photoelectric effects have been observed in MgB2 thin film fabricated by chemical vapour deposition. The rise time was -10 ns and the full width at half-maximum was -185ns for the photovoltaic pulse when the film...Fast photoelectric effects have been observed in MgB2 thin film fabricated by chemical vapour deposition. The rise time was -10 ns and the full width at half-maximum was -185ns for the photovoltaic pulse when the film was irradiated by a 308 nm laser pulse of 25 ns in duration. X-ray diffraction and the scanning electron microscope revealed that the film was polycrystalline with preferred c-axis orientation. We propose that nonequilibrium electron-hole pairs are excited in the grains and grain boundary regions for MgB2 film under ultraviolet laser and then the built-ln electric field near the grain boundaries separates carriers, which lead to the appearance of an instant photovoltage.展开更多
Microwave characteristics of MgB2/Al2O3 superconducting thin films were investigated by coplanar resonator technique. The thin films studied have different grain sizes resulting from different growth techniques. The ...Microwave characteristics of MgB2/Al2O3 superconducting thin films were investigated by coplanar resonator technique. The thin films studied have different grain sizes resulting from different growth techniques. The experimental results can be described very well by a grain-size model which combines coplanar resonator theory and Josephson junction network model. It was found that the penetration depth and surface resistance of thin films with smaller grain sizes are larger than those of thin films with larger grain sizes.展开更多
文摘Fast photoelectric effects have been observed in MgB2 thin film fabricated by chemical vapour deposition. The rise time was -10 ns and the full width at half-maximum was -185ns for the photovoltaic pulse when the film was irradiated by a 308 nm laser pulse of 25 ns in duration. X-ray diffraction and the scanning electron microscope revealed that the film was polycrystalline with preferred c-axis orientation. We propose that nonequilibrium electron-hole pairs are excited in the grains and grain boundary regions for MgB2 film under ultraviolet laser and then the built-ln electric field near the grain boundaries separates carriers, which lead to the appearance of an instant photovoltage.
基金Project supported by the National Natural Science Foundation of China （Grant No 10174006）.
文摘Microwave characteristics of MgB2/Al2O3 superconducting thin films were investigated by coplanar resonator technique. The thin films studied have different grain sizes resulting from different growth techniques. The experimental results can be described very well by a grain-size model which combines coplanar resonator theory and Josephson junction network model. It was found that the penetration depth and surface resistance of thin films with smaller grain sizes are larger than those of thin films with larger grain sizes.
