Seminar: Novel Electron Optics Combining PEEM, XPEEM, and ARPES in a Single Instrument

Photoemission Electron Microscopy (PEEM) and its variant using X-ray excitation (XPEEM), and Angle-Resolved Photoelectron Spectroscopy (ARPES) usually use different instrumentation. PEEM and XPEEM use imaging microscope columns and ARPES uses electron spectrometers, primarily hemispherical ones. In a new generation of photoelectron microscopes, we combined in one electron column PEEM, XPEEM and momentum microscopy (MM) – imaging of the backfocal plane of the objective lens. Two approaches are used for energy discrimination: Time-of-flight (ToF) recording [1], which turned out extremely powerful for time-resolved ARPES at high-harmonic sources [2] or FELs [3]. Energy-dispersive imaging using a hemispherical analyzer works with cw sources; 4.2 meV resolution have been reached using He I excitation [4]. Both, dispersive and ToF analysis are combined in a prototype instrument at the Diamond Light Source [5]. A novel type of front lens [6] enables operation at significantly reduced field strength at the sample surface. Even retarding fields are possible in order to reduce space-charge effects.

I will show examples for all operating modes: Threshold PEEM inspecting the probing region, XPEEM imaging of the chemical composition (with resolution down to < 100 nm), k-imaging for ARPES (with performance comparable to conventional ARPES). In addition, XPEEM of a converter foil enables capturing RIXS spectra. Due to reduced aberrations of the new front lens, the distance between the sample and extractor electrode can be very large (up to 14 mm), which is advantageous for future experiments at elevated pressures.

[1] K. Medjanik et al., Nat. Mater. 16, 615 (2017)
[2] S. Fragkos et al. Nature Communic. 16, 5799 (2025)
[3] V. Shokeen et al., Science Advances 10, eadj2407 (2024)
[4] G: Schönhense et al., J. Sy. Radiation 28, 1891 (2021)
[5] M. Schmitt et al., Ultramicrosc. 276 (2025) 114169
[6] O. Tkach et al., Ultramicrosc. 276 (2025) 114167