Department of Materials Science and Engineering, University of Wisconsin, Madison, Wisconsin 53706, USA.
Nano Lett. 2012 Apr 11;12(4):1765-71. doi: 10.1021/nl3001088. Epub 2012 Mar 13.
Demonstration of a tunable conductivity of the LaAlO(3)/SrTiO(3) interfaces drew significant attention to the development of oxide electronic structures where electronic confinement can be reduced to the nanometer range. While the mechanisms for the conductivity modulation are quite different and include metal-insulator phase transition and surface charge writing, generally it is implied that this effect is a result of electrical modification of the LaAlO(3) surface (either due to electrochemical dissociation of surface adsorbates or free charge deposition) leading to the change in the two-dimensional electron gas (2DEG) density at the LaAlO(3)/SrTiO(3) (LAO/STO) interface. In this paper, using piezoresponse force microscopy we demonstrate a switchable electromechanical response of the LAO overlayer, which we attribute to the motion of oxygen vacancies through the LAO layer thickness. These electrically induced reversible changes in bulk stoichiometry of the LAO layer are a signature of a possible additional mechanism for nanoscale oxide 2DEG control on LAO/STO interfaces.
LaAlO(3)/SrTiO(3) 界面可调导电性的演示引起了人们对氧化物电子结构的发展的极大关注，在这种电子结构中，电子限制可以缩小到纳米范围。虽然导电性调制的机制有很大的不同，包括金属-绝缘体相变和表面电荷写入，但通常认为这种效应是 LaAlO(3) 表面电改性的结果（由于表面吸附物的电化学离解或自由电荷沉积），导致 LaAlO(3)/SrTiO(3（LAO/STO）界面处二维电子气（2DEG）密度的变化。在本文中，我们使用压电力显微镜证明了 LAO 覆盖层的可切换机电响应，我们将其归因于氧空位通过 LAO 层厚度的运动。LAO 层体化学计量的这种电诱导可逆变化是 LAO/STO 界面上纳米尺度氧化物 2DEG 控制的可能附加机制的特征。
