高温退火对蓝宝石基片的表面形貌和对CeO2缓冲层以及Tl-2212超导薄膜生长的影响

研究了蓝宝石(1102)基片在不同温度和时间下退火时表面形貌和表面相结构的变化，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1000℃温度下退火，蓝宝石(1102)的表面首先局部区域形成台阶结构，然后表面形成叠层台阶结构，随着退火时间的延长，表面发生了台阶合并现象，表面形貌最终演化为稳定的具有光滑平台的宽台阶结构.XRD测试表明，通过高温热处理可以大幅度提高蓝宝石基片表面结构的完整性.在1000℃温度下热处理20 h的蓝宝石关键词：Tl-2212超导薄膜蓝宝石缓冲层

Effects of annealing of r-cut sapphire substrate on its surface morphology and the growth of CeO2 buffer layers and the Tl-2212 superconducting films

In this study, the surface morphology evolution and the change of the phase structure of r-cut sapphire substrates annealed at different temperatures for different time in O₂, and 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 local steps on the substrate annealed at 1000℃ is formed firstly, and then the multilayer terrace-and-step structure, yielding from prolonging annealing time, evolves into wide terrace-and-step structure with ultrasmooth terrace through the coalition of initial localized steps, which slightly tilts to the surface. XRD measurements show that the CeO₂ films prepared on r-cut sapphire annealed at the optimized conditions and the 500 nm thick Tl-2212 films grown on the CeO₂ buffer layers subsequently possess excellent in-plane and out-of plane orientation, and the annealing temperature and annealing time have strong effect on the crystalline quality of substrates and CeO₂ films. The Tl-2212 films have a high transition temperature (T_c=104.7 K), a high critical current density (J_c=3.5 MA/cm² at 77.3K and zero applied magnetic field) and a low surface resistance (R_s=390μΩ at 10GHz and 77K).