热处理对MgO基片的表面形貌以及对CeO_2和Tl-2212薄膜生长的影响

研究了MgO基片在高温退火时表面形貌和表面结构的变化,以及它对CeO2缓冲层和Tl-2212超导薄膜生长的影响。原子力显微镜(AFM)研究表明,在流动氧环境中1100℃温度下退火,MgO的表面首先由未退火时的皱褶形貌,演化为光滑表面,随着退火时间的延长,表面形貌最终演化为具有光滑基底的独立生长峰结构。XRD测试表明,通过高温热处理可以大幅度提高MgO基片表面结晶的完整性。在1100℃温度下热处理8小时的MgO基片上可以生长出具有高度c轴取向的CeO2(001)缓冲层。然后在此缓冲层上制备了厚度为500nm的外延Tl-2212超导薄膜,其临界转变温度(Tc)达到108.6K,液氮温度下临界电流密度(Jc)为2.8mA/cm2,微波表面电阻Rs(77K,10GHz)约为360.9μΩ。

Effects of annealing treatments of MgO substrates on its surface morphology and the growth of CeO2 and Tl-2212 superconducting films

We studied the surface morphology evolution and the change of the phase structure of MgO substrates annealed at different temperatures in O2.The effects of annealing conditions on the growth of CeO2 and Tl-2212 films were investigated by AFM and XRD.The results of AFM show that the smooth surface of the substrate annealed at 1100℃ is formed firstly,and then evolves into unattached outgrowth structure with ultrasmooth surface through prolonging annealing time.XRD measurements show that the annealing of MgO substrates leads to better crystallinity,which favors the epitaxial growth of(001) oriented CeO2 films.The 500nm thick Tl-2212 films grown on CeO2 buffered MgO annealed at the optimized conditions possess excellent in-plane and out-of plane orientation,which have a high transition temperature Tc of 108.6K,a high critical current density Jc of 2.8mA/cm2 at 77.3K and zero applied magnetic field and a low surface resistance Rs of 360.9μΩ at 10 GHz and 77 K.