The properties of nanostructure materials are dictated by the arrangement of their atoms, and the rapid advancement of nanotechnology has been enabled by imaging methods that can see how atoms are bonded to form nanoscale solids. Aberration corrected transmission electron microscopy can now probe individual atoms in a material, and extract information about their element type, charge transfer, and oxidization state.
I will show how we use phase contrast TEM and annular dark field scanning TEM to resolve the fundamental defect and dopant structures in 2D materials such as graphene and MoS2. This will involve revealing single Cr and V subsitutional dopants in MoS2, single Pt atoms on MoS2 surfaces, and Co doped MoS2. New research showing how 2D phases of non-layered materials can be created by the epitaxial templating on a 2D surface will be presented, such as 2D gold on graphene. Recent work on dislocation behaviour in 2D materials will be discussed, along with atomically sharp crack tip progation, shedding light on mechanical deformation properties of 2D systems.
By combining atomic level imaging and spectroscopy with density functional theory calculations we are able to resolve the 3D structure of materials and understand how charge is distributed around dopants, the emergence of unique spin transport channels in MoS2 nanoribbons, and catalytic behaviour of Pt doped MoS2. These results are connected to a larger research activity in the group involving chemical vapour deposition growth of 2D materials, their photoluminescence properties, and the fabrication of novel all 2D ultrathin opto-electronics. In-situ electronic TEM devices are made to understand how defects impact transport and in-situ high temperature measurements in the TEM reveal insights into thermal annealing procedures that clean and improve crystallinity.