Rafal E. Dunin-Borkowski1, Florian Winkler1, Amir H. Tavabi1, Juri Barthel2, Martial Duchamp1, Emrah Yucelen3, Sven Borghardt4, Beata E. Kardynal4
1. Ernst Ruska-Centre for Microscopy and Spectroscopy with Electrons and Peter Grünberg Institute 5, Forschungszentrum Jülich, D-52425 Jülich, Germany (RED-B, FW, AHT, MD)
2. Gemeinschaftslabor für Elektronenmikroskopie (GFE), RWTH Aachen University, D-52074 Aachen, Germany (JB)
3. Faculty of Physics and Center for Nanointegration (CENIDE), University of Duisburg-Essen, D-48047 Duisburg, Germany (EY)
4. Peter Grünberg Institute 9, Forschungszentrum Jülich, D-52425 Jülich, Germany (SB, BEK)
Transition metal dichalcogenides (TMDs) have attracted much attention in recent years due to their enormous potential for applications in nanoelectronic devices. However, the electrical properties of mono- or few- layer TMDs can be influenced strongly by the presence of dopants, contamination and defects, as well as by their interfaces to three-dimensional metal contacts. Here, we present high-resolution off-axis electron holography measurements of the electron wavefunction that has passed through ultra-thin flakes of WSe2. We show that the combined analysis of phase and amplitude from experimental electron holograms and corresponding simulations allows an accurate determination of the local specimen thickness, as well as the determination of a value for the mean inner potential of WSe2 of 18.9±0.8 V, which is 12% lower than the value calculated from neutral atom scattering factors. We also present preliminary electrical biasing experiments carried out on individual TMD flakes in situ in the transmission electron microscope. Electrical contacts are patterned using electron beam lithography on a SiN membrane. In order to provide a vacuum reference wave for off-axis electron holography, the TMD flakes are partly suspended over holes in the SiN membrane.
