KREIOS

Hemispherical deflection analyzers are the most widely used energy filters for state-of-the-art electron spectroscopy. Due to the high spherical symmetry, they are also well suited as imaging energy filters for electron microscopy. Here, we review the imaging properties of hemispherical deflection analyzers with emphasis on the application for cathode lens microscopy. In particular, it turns out that aberrations, in general limiting the image resolution, cancel out at the entrance and exit of the analyzer. This finding allows more compact imaging energy filters for momentum microscopy or photoelectron emission microscopy. For instance, high resolution imaging is possible, using only a single hemisphere. Conversely, a double pass hemispherical analyzer can double the energy dispersion, which means it can double the energy resolution at certain transmission, or can multiply the transmission at certain energy resolution.

C. Tusche, Y. J. Chen, C. M. Schneider and J. Kirschner
Ultramicroscopy 206 (2019)

The implementation of graphene in semiconducting technology requires precise knowledge about the graphene–semiconductor interface. In our work the structure and electronic properties of the graphene/n-Ge(110) interface are investigated on the local (nm) and macro (from μm to mm) scales via a combination of different microscopic and spectroscopic surface science techniques accompanied by density functional theory calculations. The electronic structure of freestanding graphene remains almost completely intact in this system, with only a moderate n-doping indicating weak interaction between graphene and the Ge substrate. With regard to the optimisation of graphene growth it is found that the substrate temperature is a crucial factor, which determines the graphene layer alignment on the Ge(110) substrate during its growth from the atomic carbon source. Moreover, our results demonstrate that the preparation route for graphene on the doped semiconducting material (n-Ge) leads to the effective segregation of dopants at the interface between graphene and Ge(110). Furthermore, it is shown that these dopant atoms might form regular structures at the graphene/Ge interface and induce the doping of graphene. Our findings help to understand the interface properties of the graphene–semiconductor interfaces and the effect of dopants on the electronic structure of graphene in such systems.

J. Tesch, F. Paschke, M. Fonin, M. Wietstruk, S. Böttcher, R. J. Koch, A. Bostwick, C. Jozwiak, E. Rotenberg, A. Makarova, B. Paulus, E. Voloshina, Y. Dedkov
Nanoscale, 10, pp. 6088-6098