Artificial charge-modulation in atomic-scale perovskite titanate superlattices
Artificial charge-modulation in atomic-scale perovskite titanate superlattices
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DOI：
10.1038/nature00977
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发表时间：
2002-09-26
期刊：
影响因子：
64.8
通讯作者：
Hwang, HY
中科院分区：
文献类型：
--
作者：
Ohtomo, A;Muller, DA;Hwang, HY
复合氧化物中电荷屏蔽的性质和长度尺度是广泛系统的基础，涵盖陶瓷压敏电阻器（变阻器），氧化物隧道结和混合价化合物中的电荷有序（1-6）。在混合价化合物中，电荷分离的程度、长度尺度和取向都有很大的变化：这些都是深入的理论研究的主题（7-11），但对微观电子结构知之甚少。在这里，我们已经制作了一个理想化的结构来研究这些问题，通过生长原子突变层的LaTi 3 +O3嵌入SrTi 4 +O3。利用原子尺度的电子束，我们观察到了额外的电子在钛位上的空间分布。这种分布导致金属导电性，即使超晶格结构是基于两个绝缘体。尽管界面的化学性质，我们发现，一个最小的厚度为五个LaTiO 3层所需的中心钛网站，以恢复批量样的电子性能。这代表了一个框架内，短长度尺度的电子响应可以探测和纳入薄膜氧化物异质结构。
The nature and length scales of charge screening in complex oxides are fundamental to a wide range of systems, spanning ceramic voltage-dependent resistors (varistors), oxide tunnel junctions and charge ordering in mixed-valence compounds(1-6). There are wide variations in the degree of charge disproportionation, length scale, and orientation in the mixed-valence compounds: these have been the subject of intense theoretical study(7-11), but little is known about the microscopic electronic structure. Here we have fabricated an idealized structure to examine these issues by growing atomically abrupt layers of LaTi3+O3 embedded in SrTi4+O3. Using an atomic-scale electron beam, we have observed the spatial distribution of the extra electron on the titanium sites. This distribution results in metallic conductivity, even though the superlattice structure is based on two insulators. Despite the chemical abruptness of the interfaces, we find that a minimum thickness of five LaTiO3 layers is required for the centre titanium site to recover bulk-like electronic properties. This represents a framework within which the short-length-scale electronic response can be probed and incorporated in thin-film oxide heterostructures.