非平衡双轴失配应变对BST薄膜相图的影响

Effects of nonequally biaxial misfit strains on the phase diagram of epitaxial BST ferroeiectric thin films

用朗道———德文希尔理论研究了非平衡双轴失配应变对单畴外延钛酸锶钡(BST)薄膜相变的影响,得到了室温下生长在四方基底上的BST50/50薄膜的“失配应变—失配应变”相图和能量图。结果表明在BST50/50薄膜中由于非平衡双轴失配应变的作用,出现了两个在平面内的四方铁电相,即:a1相(P1≠0,P2=P3=0)和a2相(P2≠0,P1=P3=0),而这在平衡失配应变下是不存在的。室温下,非平衡失配应变在一定范围内不能使BST50/50中的顺电相消失。

The effects of nonequally biaxial in - plan misfit strains on the phase diagrams of single - domain epitaxial barium strontium titanate thin film are investigated by Landau - Devonshire theory. We obtain the “misfit strain - misfit strain” phase diagram and energy diagram for BST thin film grown on tetragonal base at room temperature. It is found that nonequally biaxial in - plan misfit strains cause the presence of two in - plan tetragonal ferroelectric phases, a1 （ P1 ≠ 0, P2 = P3 = 0） 和 a2（P2 ≠ 0, P1 = P3 = 0） in BST50/50 thin film,which do not exit if the misfit strain are equally biaxial. The paraelectric state of BST50/50 thin film doesn＇t disappear under the nonequally misfit strains at the room temperature.