Applications of a scanning low energy electron microscope

Date: 
Monday, December 11, 2017 - 4:00pm
Speaker: 
Tomáš Řiháček
Speaker's Institution: 
Institute of Scientific Instruments of the CAS, Brno, Czech Republic

Scanning low energy electron microscopes (SLEEM) operating with primary beam energy below 500 eV have proved to be a powerful tool for investigating many samples that are difficult to being observed using standard (S)TEM techniques. In case of low energies an appropriate strategy of collecting detecting signal electrons is important to have a sufficient signal and reasonable contrast. Many principles were developed for this purpose and nowadays, they are a standard part of commercial machines.

Although it is in principle possible to investigate biological materials using standard (S)TEM techniques, it usually requires a sophisticated and time demanding sample preparation. This procedure may be often significantly reduced by lowering a primary beam energy down to hundreds of eV (or even lower). Moreover, one may avoid a radiation damage of the sample. By finding a proper primary beam energy, a sample charging may be significantly reduced or even completely eliminated. On the other hand, there are materials that are nearly transparent for fast electrons (e.g. graphene) and thus unobservable unless the energy is decreased to a few electronvolts. Together with an ultra-high vacuum, SLEEM offers a unique way of investigating surfaces because of a rather small interaction volume and clean sample-vacuum interface.

Electron vortex beams (EVBs), being the beams with well-defined orbital angular momentum and thus an induced magnetic moment, they are a promising tool for several applications. In order to make use of numerous advantages of the S(LE)EM, a creation and applications of electron vortices within a scanning electron microscope are considered.

 

Acknowledgements

The work was supported by the project  no: TE01020118 of the Technology Agency of the Czech Republic and by VASE GRANTY, MEYS CR (LO1212), its infrastructure by MEYS CR and EC (CZ.1.05/2.1.00/01.0017) and by CAS (RVO:68081731).