Local study of the band gap and structure of diamond based nanomaterials by analytical transmission electron microscopy
11 October 2018
Campus Groenenborger, U0.24 - Groenenborgerlaan 171 - 2020 Antwerpen (route: UAntwerpen, Campus Groenenborger
Organization / co-organization:
Department of Physics
PhD defence Svetlana Korneychuk - Faculty of Science, Department of Physics
Transmission electron microscopy (TEM) is an ideal tool to study the microstructure and composition of materials at a local scale, routinely providing atomic resolution. Combination of TEM with electron energy loss spectroscopy (EELS) allows studying the composition of materials, including the chemical bonding, down to sub-ångström spatial resolution and even investigate dielectric properties including the band gaps with nanometer resolution.
In the first part of the thesis we apply analytical TEM on diamond-related materials, for example, to locally characterize large field emitters based on diamond, or to reveal crystalline structure of the platelet defect in natural diamond.
The second part of the thesis develops the methodology of measuring the band gap of diamond and other materials. At first we show how to avoid retardation losses, such as Cherenkov radiation, and collect a clean direct band gap signal with a simple microscope setup using a circular (Bessel) aperture. Making use of the non-zero momentum transfer in EELS, we measure the indirect band gap of diamond and other indirect transitions in the diamond band structure. Finally, we discuss the emerging possibility to partly reconstruct the band structure of diamond with EELS.