Patterning Oxide Nanopillars at the Atomic Scale by Phase Transformation

Phase transformations in crystalline materials are common in nature and often modify dramatically properties of materials. The ability to precisely control them with a high spatial precision represents a significant step forward in realizing new functionalities in confined dimensions. However, such control is extremely challenging particularly at the atomic scale due to the intricacies in governing thermodynamic conditions with a high spatial accuracy. Here, we apply focused electron beam of a scanning transmission electron microscope to irradiate SrNbO_3.4 crystals and demonstrate a precise control of a phase transformation from layered SrNbO_3.4 to perovskite SrNbO₃ at the atomic scale. By purposely squeezing O atoms out of the vertex-sharing NbO₆ octahedral slabs, their neighboring slabs zip together, resulting in a patterning of SrNbO₃ nanopillars in SrNbO_3.4 matrix. Such phase transformations can be spatially manipulated with an atomic precision, opening up a novel avenue for materials design and processing and also for advanced nanodevice fabrication.