The smooth (001) surfaces of SrTiO3 (STO) single crystals were investigated by the reflection high-energy electron diffraction method in the temperature range from 5.5 to 300 K. The Raman scattering confirmed the high quality of STO samples. Five structural anomalies were found depending on temperature. The antiferrodistortive phase transition from the cubic structure to tetragonal, observed in the STO bulk at 105 K, on the surface extends from 70 to 120 K. The anomalies below 7 K and about 35 K are similar to those in the bulk considered as a crossover between the growth of the ferroelectric atomic displacements with decreasing temperature and quantum-mechanical stabilization of this growth due to the zero-point atomic motion. The other two anomalies are related only to a surface. Differentiation of lattice parameters depending on the depth from a surface revealed nonmonotonic changes, which could be used for detecting the structural transformations. The comprehensive understanding of the structural properties of ABO3 perovskite surfaces is important for elucidating the nature of the effects at the boundary of metallic ferromagnetism in similar materials.

中文翻译：

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SrTiO3单晶(001)表面的低温结构转变

通过反射高能电子衍射法在 5.5 到 300 K 的温度范围内研究了 SrTiO3 (STO) 单晶的光滑 (001) 表面。拉曼散射证实了 STO 样品的高质量。根据温度发现了五个结构异常。从立方结构到四方结构的反铁扭曲相变，在 105 K 的 STO 块体中观察到，表面上从 70 到 120 K。低于 7 K 和大约 35 K 的异常与被认为是交叉的块体中的那些相似在铁电原子位移随温度降低的增长与由于零点原子运动导致的这种增长的量子力学稳定性之间。另外两个异常只与一个表面有关。根据距离表面的深度对晶格参数进行区分显示出非单调变化，可用于检测结构转变。全面了解 ABO3 钙钛矿表面的结构特性对于阐明类似材料中金属铁磁性边界处的效应性质非常重要。