Abstract

A new generation of electron beam monochromators has recently pushed the energy resolution of (scanning) transmission electron microscopes deep into the sub 20meV range. In addition to the obvious increase in resolution which has made exploring the phonon region of the EELS spectrum possible, the increased flexibility of these instruments is proving hugely advantageous for materials science investigations. Recent applications include the observations of complex electronic transitions such as excitons in MoS2, van Hove singularities in carbon nanotubes in real and momentum space, as well as mapping minute changes in band gap energies of semi-conductor materials as a function of local structure and chemistry. The energy resolution, beam current and electron optics can be adjusted seamlessly and traded off each other as necessary within a greatly increased range, as will be illustrated on a number of systems studied using a Nion UltraSTEM100MC ‘Hermes’ instrument recently installed at the SuperSTEM Laboratory.