He Feizhou, Wells B O, Shapiro S M
Department of Physics, University of Connecticut, Storrs, Connecticut 06269, USA.
Phys Rev Lett. 2005 May 6;94(17):176101. doi: 10.1103/PhysRevLett.94.176101. Epub 2005 May 2.
SrTiO3 thin films were used as a model system to study the effects of strain and epitaxial constraint on structural phase transitions of perovskite films. The basic phenomena revealed will apply to a variety of important structural transitions including the ferroelectric transition. Highly strained SrTiO3 films were grown on different substrates, providing both compressive and tensile strain. The measured strain-temperature phase diagram is qualitatively consistent with theory; however, the increase in the phase transition temperature is much larger than predicted. Because of the epitaxial strain and substrate clamping, the SrTiO3 lattice is tetragonal at all temperatures. The phase transitions involve only changes in internal symmetry. The low temperature phase under tensile strain has a unique structure with orthorhombic Cmcm space group but a tetragonal lattice, an interesting consequence of epitaxial constraint.
钛酸锶（SrTiO₃）薄膜被用作一个模型系统，以研究应变和外延约束对钙钛矿薄膜结构相变的影响。所揭示的基本现象将适用于包括铁电转变在内的各种重要结构转变。在不同衬底上生长了高度应变的SrTiO₃薄膜，提供了压缩应变和拉伸应变。测量得到的应变 - 温度相图在定性上与理论一致；然而，相变温度的升高比预测的要大得多。由于外延应变和衬底夹持作用，SrTiO₃晶格在所有温度下均为四方晶系。相变仅涉及内部对称性的变化。拉伸应变下的低温相具有独特的结构，其空间群为正交晶系的Cmcm，但晶格为四方晶系，这是外延约束的一个有趣结果。
