Laboratory UPS with PEEM MICROANALYSER and HIS 13 High Intensity UV Source

Micro-UPS in the valence band region of MoTe₂ using the PEEM-MICROANALYSER and a HIS 13 High Intensity VUV Source for HeI excitation. The microspectroscopy analysis area was selected down to 30 µm diameter using the PEEM's iris aperture. Microspectroscopy was carried out on a MoTe₂ sample cleaved in UHV. While a conventional mercury high pressure lamp was used to obtain the surface image (200 µm in diameter), the UPS experiment employed the HIS 13 VUV excitation source (HeI: h_n = 21.2 eV). Some defect features (red) are visible on the otherwise homogeneous Van-der-Waals surface. While UPS spectra show the same valence band structure indicative of MoTe₂ in both areas, the defects show a significantly increased secondary electron yield explaining the observed image contrast.