Nanoscale control of materials properties by in-situ defect engineering

对节能电子产品日益增长的需求，再加上信息技术的发展，通过需要在纳米尺度上设计材料特性的新方法，正在推动材料科学领域的一场革命。目前，最广泛使用的设计电子和磁性的方法之一——用于信息技术的新发展——是通过非原位缺陷控制，如掺杂。这种方法的成功在半导体工业中得到了例证，在半导体工业中，p型和n型掺杂被用来制造晶体管——现代计算机技术的基石。尽管这些经典方法取得了成功，但它们通常是非原位的，并且往往有基本的限制，使它们无法在原子尺度上制造结构，例如光刻技术中的衍射极限。本提案将通过两个研究目标来解决这些挑战：i)建立一种新的方法，允许材料性能的原位原子尺度设计；Ii)使用这种原位方法来创建具有独特功能的新型受限状态。这些目标将通过施加电场，通过导电原子力显微镜，以局部受限的方式改变缺陷结构和相应的局部价来实现。将使用两种模板系统来证明这种变化可以独立于材料的组成或对称性来实现：由于它们具有迷人的电子和磁畴和畴壁性质，特定的材料将是腔隙尖晶石和六方锰矿。通过局部修饰价（通过电场诱导缺陷），可以驱动对称性和结构的变化，从而引起晶体局部电子和磁性行为的改变。所有这些都有望使新的状态、性质和现象以原子尺度的空间精度被写入材料中。建立这种纳米工程材料特性的基本新方法将为创造和控制电子和磁性提供一条新途径，这是下一代节能电子系统的起点。

The growing demand for energy-efficient electronics, coupled with developments in information technology, are fuelling a revolution within materials science through the need for new approaches to engineer material properties at the nanoscale. Currently, one of the most widely used ways to engineer electronic and magnetic properties – use for new developments in information technology – is via ex-situ defect control, such as doping. The success of this approach is exemplified by the semiconductor industry in which p- and n-type doping is used to create transistors: the building blocks for modern computer technologies. As successful as such classic approaches are, they are typically ex-situ and often have fundamental limitations that prevent them fabricating structures on the atomic scale, e.g., the diffraction limit in lithographic techniques. This proposal will address these challenges by with two research goals: i) establishing a new approach that allows in-situ atomic-scale design of material properties; ii) using this in-situ methodology to create novel confined states with unique functionalities. These goals will be achieved by applying electric fields, via conductive atomic force microscopy, to change the defect structure and, correspondingly, the local valencies in a locally confined way. Two template systems will be used to show such changes can be achieved independent of materials composition or symmetry: the specific materials will be the lacunar spinels and the hexagonal manganites due to their established zoo of fascinating electronic and magnetic domain and domain wall properties. By locally modification of the valencies (via electric field induced defects) changes in the symmetries and structures can be driven, causing a modification of the local electronic and magnetic behaviours of the crystals. All of this is expected to allow novel states, properties and phenomena to be written into materials in-situ with atomic scale spatial precision. Establishing this fundamentally new approach to nanoengineer material properties will offer a new route towards creating and controlling electronic and magnetic properties, a starting point for the next generation of energy efficient electronic systems.