报告题目： Polarization-Related Electronic Properties of Complex Oxides
报告人： 美国Nebraska大学Alexei Grouverman教授，美国物理学会会士、Nebraska大学物理系Charles Bessey讲席教授
报告时间：5月7日，星期四，下午2点
报告地点： 科学楼902
报告摘要：
Recently it was demonstrated that the conductivity of the LaAlO3/SrTiO3 (LAO-STO) interface can be reversibly tuned through a switchable electromechanical response arising from the LAO overlayer in the LAO-STO heterostructures. Bulk LaAlO3 (LAO) is a typical perovskite, which shows paraelectric behavior at room temperature. In this study, we have investigated switchable dielectric propeties of the LAO ultrathin (several unit cells) films grown on top of lattice-matched conducting oxide Sr0.2Ca0.8RuO3 (SCRO) on the (001) (LaAlO3)0.3–(Sr2AlTaO3)0.7 (LSAT) substrate. Piezoresponse force microscopy (PFM) studies performed on the LAO/SCRO/LSAT heterostructures show a genuine switchable hysteretic electromechanical behavior resembling that one observed in ferroelectric films associated with induced polarization in the LAO layer. An insight into the underlying mechanism of such behavior has been gained by using temperature-dependent PFM spectroscopic, dielectric and structural measurements. The effect of inhomogeneous strain gradient induced by the PFM probe on polarization in LAO as well as 2DEG conductivity at the LAO-STO interface has been also studied. The proposed mechanism of switchable electromechanical response should be active in many other oxide heterosystems, but its detailed manifestation likely depends on a number of subtleties, such as oxygen octahedra rotations and distortions, strain, and lattice coupling at the nanoscale. Control of this phenomenon will enable new structures and devices that exploit nanoscale electromechanical coupling.
