脉冲激光沉积法原位后退火生长MgB_2薄膜的研究

Study on In Situ Annealing Superconducting MgB_2 Films Prepared by Pulsed Laser Deposition

采用脉冲激光沉积的方法在Al2O3(0001)基片上先生成MgB混和薄膜,然后采用原位后退火的方法生成MgB2超导薄膜,采用磁测量(MT)、X射线衍射、扫描电子显微镜技术分析了各种沉积及退火条件对MgB2超导薄膜表面形貌、晶体结构、超导电性的影响。在沉积温度为200℃,退火时间5min时,改变退火温度得到一组薄膜,研究退火温度对超导薄膜性质的影响,得到了转变温度退火温度曲线。在退火温度为670℃、720℃时,得到了最高的临界转变温度Tc=33K,X射线衍射结果表明此时的薄膜有c轴取向。同时比较了在200℃下沉积,在670℃下分别退火不同时间的薄膜的超导性质。还比较了分别在不同温度下沉积,然后在670℃下退火5min的薄膜的超导性质。结果表明,沉积温度和退火温度、退火时间极大的影响了薄膜的各种性质。

In Situ annealed superconducting thin films are acquired by pulsed laser deposition method. With SEM, X-ray diffraction analysis, magnetic measurement （by Magnetic Property Measurement System）, the effects of growth and annealing conditions are analyzed. It indicats that the growth temperature, annealing temperature and time greatly affects the quality of MgB2 films. The films grown at 200 ℃ , annealed for 5 min at different temperatures ranged from 280 ℃ to 820 ℃ are carefully compared to study the effect of annealing temperature. The film acquired at the highest Tc of 33 K grows at 200℃ , annealed at 670, 720 ℃ for 5 min, X-ray analysis shows that it has c axis orientation. The films which were grown at 200 ℃ and annealed at 670 ℃ for different time are compared to study the effect of annealing temperature. The films grown at different temperatures but all annealed at 670 ℃ for 5 min are also compared to study the effect of growth temperature.