Probing bulk electronic structure with a laboratory-based hard x-ray angle-resolved photoemission spectrometer

Hard x-ray angle-resolved photoemission (HARPES) employing multi-keV x-rays as the excitation source has recently emerged as a powerful tool for the direct measurement of momentum-resolved bulk electronic structure [1-3]. To date, comprehensive HARPES spectroscopic studies have only been feasible at large-scale national synchrotron facilities. Here, we describe a newly completed laboratory-based hard x-ray photoemission spectrometer system with HARPES capabilities. The system utilizes a high-flux (3E9 ph/s) high-resolution (<0.45 eV) monochromated Cr Kα x-ray source tuned to the intermediate hard/tender energy regime (5.4 keV), which enables bulk- and buried-layer/interface sensitivity (up to 10 nm deep) while still being sensitive to the valence-band states due to appreciable photo-ionization cross sections. We present a wide range of examples of angle-resolved investigations of solids, including core-level and valence-band spectroscopy, momentum-resolved band structure mapping, and element-sensitive x-ray photoelectron diffraction.

[1] A. X. Gray et al., Nature Mat. 11, 957 (2012)
[2] A. X. Gray et al., Nature Mat. 10, 759 (2011)
[3] S. Nemšák et al., Nature Comm. 9, 3306 (2018)