From Two to Three Dimensions: the Mutual Benefits of Cross-Sectional Scanning Tunnelling Microscopy and Atom Probe Tomography

The microscopy techniques of cross-sectional scanning tunnelling microscopy (XSTM) and atom probe tomography (APT) both offer atomic-level characterization, yet have wildly different representations. Whilst XSTM is strictly a surface technique, where atoms are imaged directly, with great precision, APT is able to produce a 3D map of a specimen, determining atomic locations through reconstruction. APT has an extremely high mass sensitivity, allowing accurate determination of chemical species of an atom, but XSTM is measuring local electronic properties, able to probe the band structure. By analysing semiconductor nanostructures, such as quantum dots, we are able to juxtapose these two complimentary techniques. This allows us to both benchmark the capabilities of APT against the established XSTM technique and also verify structural composition inferred from planar XSTM images through comparison to the richer volumetric APT view. The unique capabilities of both can be harnessed to achieve a fuller understanding of nanostructural properties.