Mechanisms for hetero-epitaxial nucleation of YBa2Cu3O∼6.1 at the buried precursor/SrTiO3 interface in the postdeposition reaction process
Mechanisms for hetero-epitaxial nucleation of YBa2Cu3O∼6.1 at the buried precursor/SrTiO3 interface in the postdeposition reaction process
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DOI：
10.1063/1.1436285
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发表时间：
2002-01
影响因子：
4
通讯作者：
Lijun Wu;V. Solovyov;H. Wiesmann;Y. Zhu;M. Suenaga
中科院分区：
文献类型：
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作者：
Lijun Wu;V. Solovyov;H. Wiesmann;Y. Zhu;M. Suenaga
已确定的机制YBa 2Cu 3 O-6.1（YBCO）在前体膜和SrTiO 3之间的掩埋界面的异质外延成核的所谓BaF 2过程，这是一个后沉积反应过程的外延YBCO薄膜的合成。结果表明：（1）（Y，Ba）-氟氧化物（一种中间相）与SrTiO_3的化学亲合力很强;（2）（111）面与SrTiO_3的（001）面的外延排列降低了YBCO的形成激活势垒。在薄膜（<2-3 μm）中，YBCO晶核的c轴垂直于SrTiO_3表面，直接由这种定向的氟氧化物形成。然而，在厚膜（5 μm）中，这种氟氧化物分解成无序的过渡立方相，然后有序形成具有三种取向变体的YBCO核，一种是c轴垂直于SrTiO 3的（001）面，另两种是c轴平行于SrTiO 3的（001）面。
The mechanisms have been identified for the hetero-epitaxial nucleation of YBa2Cu3O∼6.1 (YBCO) at the buried interface between a precursor film and SrTiO3 for the so-called BaF2 process which is a postdeposition reaction process for the synthesis of epitaxial YBCO films. It is shown that the preferential nucleation of YBCO at the interface is due to (1) the strong chemical affinity of the (Y, Ba)-oxy-fluoride, an intermediate phase, to SrTiO3 and (2) the epitaxial alignment of its (111) planes with the (001) surface of the SrTiO3 which reduces the activation barrier for the formation of YBCO. In thin films (<2–3 μm) the YBCO nuclei, whose c axes are perpendicular to the SrTiO3 surface, form directly from this aligned oxy-fluoride. In thick films (5 μm), however, this oxy-fluoride decomposes into a disordered transitory cubic phase which then orders to form YBCO nuclei with three orientational variants, one with its c axis perpendicular and two with their c axes parallel to the (001) plane of SrTiO3.