Tuning the Electron Gas at an Oxide Heterointerface via Free Surface Charges
Tuning the Electron Gas at an Oxide Heterointerface via Free Surface Charges
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DOI：
10.1002/adma.201004673
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发表时间：
2011-04
影响因子：
29.4
通讯作者：
Yanwu Xie;C. Bell;Y. Hikita;H. Hwang
中科院分区：
文献类型：
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作者：
Yanwu Xie;C. Bell;Y. Hikita;H. Hwang
氧化物异质界面是凝聚态科学中最令人兴奋的材料体系之一。一个显著的例子是LaAlO{sub 3}/SrTiO{sub 3} （LAO/STO）界面，这是一个模型系统，其中在两个带绝缘体之间形成高度移动的电子气体，表现出二维超导性和不寻常的磁输运性质。调节这种电子气体的理想工具是静电场效应。原则上，静电场可以由由于极化而产生的束缚电荷（如在正常和铁电场效应中）或通过添加多余的自由电荷产生。在以往的研究中，利用正态场效应已经实现了对LAO/STO界面载流子密度和迁移率的大调制。然而，自由电荷产生的场效应很少受到重视。由于自由电荷通常不稳定，即使在传统的半导体器件中，这个问题也几乎没有得到解决。在这里，我们展示了通过使用导电原子力显微镜（AFM）记录的自由表面电荷对LAO/STO界面电导率的明确调整。发现载流子密度的调制是可逆的，非易失性的，并且惊人地大，{大约}3 x 10{sup 13} cm{sup -2}，与正常场效应的最大调制相当。我们的发现揭示了自由电荷在控制这种氧化物界面导电性方面的效率，并表明这种技术可以更广泛地扩展到其他氧化物体系。«少
Oxide heterointerfaces are emerging as one of the most exciting materials systems in condensed matter science. One remarkable example is the LaAlO{sub 3}/SrTiO{sub 3} (LAO/STO) interface, a model system in which a highly mobile electron gas forms between two band insulators, exhibiting two dimensional superconductivity and unusual magnetotransport properties. An ideal tool to tune such an electron gas is the electrostatic field effect. In principle, the electrostatic field can be generated by bound charges due to polarization (as in the normal and ferroelectric field effects) or by adding excess free charge. In previous studies, a large modulation of the carrier density and mobility of the LAO/STO interface has been achieved using the normal field effect. However, little attention has been paid to the field effect generated by free charges. This issue is scarcely addressed, even in conventional semiconductor devices, since the free charges are typically not stable. Here, we demonstrate an unambiguous tuning of the LAO/STO interface conductivity via free surface charges written using conducting atomic force microscopy (AFM). The modulation of the carrier density was found to be reversible, nonvolatile and surprisingly large, {approx}3 x 10{sup 13} cm{sup -2}, comparable to the maximum modulation by the normal field effect.more » Our finding reveal the efficiency of free charges in controlling the conductivity of this oxide interface, and suggest that this technique may be extended more generally to other oxide systems.« less