沉积速率对MOCVD-Y(Gd)BCO超导薄膜结构与性能的影响研究

Effect of deposition rate on the structure and performance of MOCVD-Y(Gd)BCO high-temperature superconducting films

第二代高温超导带材制备中提升超导层的沉积速率有助于降低带材成本。本文基于自主设计的MOCVD系统在LaMnO_(3)/epi-MgO/IBAD-MgO/Y_(2)O_(3)/Al_(2)O_(3)/哈氏合金模板基带上沉积Y(Gd)BCO高温超导薄膜。通过改变前驱体进液速率实现沉积速率的调控,采用多种分析测试方法研究Gd_(0.5)Y_(0.5)Ba_(2)Cu_(3)O_(7)-δ(Y(Gd)BCO)薄膜结构与性能。在加热温度和气氛等工艺条件保持不变的前提下,调节沉积速率为520 nm/min时,制备得到约250 nm厚的Y(Gd)BCO超导层结构性能良好,在0 T,77 K的条件下,临界电流密度(J_(c))可达到3.5 MA/cm^(2),临界电流(I_(c))为89 A/cm,面内、面外半高宽值分别为2.36°和1.69°。即使提高沉积速率到1000 nm/min,虽然Y(Gd)BCO薄膜表面出现了a轴晶粒,但是Jc仍能保持在一个较优的水平。实验结果表明,MOCVD方法可以实现高温超导薄膜的高速率沉积。

Increasing deposition rate of superconducting films is an effective way to cut the cost of the second generation high temperature superconducting tapes.In this paper,Y(Gd)BCO superconducting films were deposited on the template of LaMnO_(3)/epi-MgO/IBAD-MgO/Y_(2)O_(3)/Al_(2)O_(3)/Hastelloy alloy based on a self-designed MOCVD system.Adjusting the precursor feeding rate,the changes of the structure and performance of Y(Gd)BCO films at different deposition rates were analyzed by different test methods.When the parameters such as heating temperature and atmosphere are kept constant,and the deposition rate is 520 nm/min,the critical current density(J_(c))and critical current(I_(c))of~250 nm thick Y(Gd)BCO films can reach 3.5 MA/cm^(2)and 89 A/cm(0 T,77 K),respectively.The FWHM values of the in-plane and out-ofplane texture are 2.36°and 1.69°,respectively.It should be noted that as the deposition rate continues to increase,the Jc remains at a superior level although some a-axis-oriented Y(Gd)BCO grains appear on the surface of the films,indicating that the superconducting thin films could be deposited at a high deposition rate with MOCVD.