Thickness-dependent structural phase transition of strained SrRuO3 ultrathin films: The role of octahedral tilt
Thickness-dependent structural phase transition of strained SrRuO3 ultrathin films: The role of octahedral tilt
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DOI：
10.1103/physrevb.84.104101
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发表时间：
2011-09-01
影响因子：
3.7
通讯作者：
Noh, T. W.
中科院分区：
文献类型：
--
作者：
Chang, Seo Hyoung;Chang, Young Jun;Noh, T. W.
我们在SrTiO3 (STO)（001）衬底上生长了外延SrRuO3 （SRO）薄膜，SRO层厚度(t)在10到200个伪晶胞（uc）之间。利用立方SRO表面的方网，我们能够在室温下外延稳定t = 19 uc的超薄膜的四方SRO相，这些超薄膜在室温下具有类似于块状SRO的正交晶体结构。随着温度的升高，正交膜在T-OT时发生了向四方相的结构转变。室温下的T-OT值和正交系数随膜厚的减小而减小。我们还观察到半阶Bragg反射，表明这种四边形结构是由于抑制了RuO6八面体的倾斜角度而产生的。在t(c)附近观测到的临界厚度与18uc相似，比最近的理论预测（即小于2uc）要大得多[J]。他，A. Borisevich， S. V. Kalinin， S. J. Pennycook和S. T. Pantelides，物理学家。科学通报，2009(1)。因此，这项工作表明，界面上的晶格对称性失配在决定钙钛矿薄膜的结构特性方面起着重要作用。
We grew epitaxial SrRuO3 (SRO) films on SrTiO3 (STO) (001) substrates with SRO layer thicknesses (t) between 10 and 200 pseudocubic unit cells (uc). Using the square net of the cubic STO surface, we were able to epi-stabilize the tetragonal SRO phase at room temperature for ultrathin films with t = 19 uc have an orthorhombic crystal structure similar to that of bulk SRO at room temperature. With increasing temperature, the orthorhombic films undergo a structural transition to the tetragonal phase at T-OT. The value of T-OT and the orthorhombicity factor at room temperature are reduced with decreasing film thickness. We also observed half-order Bragg reflections, indicating that the tetragonal structure arises from the suppression of the tilt angle of RuO6 octahedra. The observed critical thickness around t(c) similar to 18 uc is much larger than the recent theoretical prediction (i.e., less than 2 uc) [J. He, A. Borisevich, S. V. Kalinin, S. J. Pennycook, and S. T. Pantelides, Phys. Rev. Lett. 105, 227203 (2010)]. This work thus demonstrates that the lattice symmetry mismatch at the interface plays an important role in determining the structural properties of perovskite films.