Spatially Resolved Analysis of the Electronic Properties of WS2-Coated Carbon Nanotubes Using EELS in a TEM

Using the line focusing properties of the Gatan Imaging Filter (GIF) fitted to a transmission electron microscope (TEM), it is possible to extract electron energy loss (EEL) spectra with sub-nanometre spatial resolution from interfaces, whilst still maintaining parallel illumination. This non-contact technique allows for the investigation of the electronic properties of heterojunctions on a nanometre and sub-nanometre scale. Here we investigate the dielectric properties of the tungsten disulfide coating of a multi-walled carbon nanotube (MWCNT), by examining the change in the plasmon energy as a function of the coating s thickness. We show that for coating layer thicknesses above 5 monolayers (approx. 3.1 nm), there is a change in the plasmon region of the EEL spectra across the interface that indicates a change in the dielectric properties.