Field Mapping in Semiconductors by Off-axis Electron Holography: From Devices to Graphene and Single Dopant Atoms

Off-axis electron holography is an electron microscopy-based technique that allows the electrostatic and magnetic fields in and around a specimen to be measured with nm-scale resolution. The continuous reduction in the size of semiconductor devices means that information about the distribution of strain fields and active dopants at a nanometre scale is required in order to understand how these properties affect their electrical performance. Indeed, the reduction in the size of these devices is in some ways beneficial for electron holography as the higher dopant concentrations that are used are less affected by artefacts from specimen charging and preparation. As these devices are miniaturised further, what was once known as a very high dopant concentration will be only a few atoms and the positions of these individual atoms will affect the properties of the device. As a consequence we are working towards the detection of single dopant atoms by off-axis electron holography.