Nanoscale control of materials properties by in-situ defect engineering

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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.