Department of Physics, Case Western Reserve University, Cleveland, Ohio 44106, USA.
Department of Materials Science and Engineering, Case Western Reserve University, Cleveland, Ohio 44106, USA.
Sci Rep. 2017 Mar 15;7:44361. doi: 10.1038/srep44361.
The crystal structure of bulk SrTiO(STO) transitions from cubic to tetragonal at around 105 K. Recent local scanning probe measurements of LaAlO/SrTiO (LAO/STO) interfaces indicated the existence of spatially inhomogeneous electrical current paths and electrostatic potential associated with the structural domain formation in the tetragonal phase of STO. Here we report a study of temperature dependent electronic transport in combination with the polarized light microscopy of structural domains in mesoscopic LAO/STO devices. By reducing the size of the conductive interface to be comparable to that of a single tetragonal domain of STO, the anisotropy of interfacial electron conduction in relationship to the domain wall and its direction was characterized between T = 10-300 K. It was found that the four-point resistance measured with current parallel to the domain wall is larger than the resistance measured perpendicular to the domain wall. This observation is qualitatively consistent with the current diverting effect from a more conductive domain wall within the sample. Among all the samples studied, the maximum resistance ratio found is at least 10 and could be as large as 10 at T = 10 K. This electronic anisotropy may have implications on other oxide hetero-interfaces and the further understanding of electronic/magnetic phenomena found in LAO/STO.
块状 SrTiO（STO）的晶体结构在大约 105 K 时从立方相转变为四方相。最近对 LaAlO/SrTiO（LAO/STO）界面的局部扫描探针测量表明，在 STO 的四方相形成中存在与结构畴相关的空间不均匀电流路径和静电势。在这里，我们报告了一项关于电子输运随温度变化的研究，并结合了介观 LAO/STO 器件中结构畴的偏振光显微镜研究。通过将导电界面的尺寸减小到与 STO 的单个四方畴相当，在 T = 10-300 K 范围内，我们对界面电子输运的各向异性与畴壁及其方向进行了表征。结果发现，与垂直于畴壁测量的电阻相比，电流平行于畴壁测量的四点电阻更大。这一观察结果与样品中更具导电性的畴壁从电流分流的效果定性一致。在所研究的所有样品中，在 T = 10 K 时发现的最大电阻比至少为 10，最大可达 10。这种电子各向异性可能对其他氧化物异质界面以及对在 LAO/STO 中发现的电子/磁性现象的进一步理解有影响。
