Current performance and future perspectives of a photoelectron momentum microscope at the Taiwan Photon Source
Tzu-Hung Chuang1*, Chuan-Che Hsu1,2, Heng-Wen Wei1, Der-Hsin Wei1,3
1Scientific Research Division, National Synchrotron Radiation Research Center, Hsinchu, Taiwan
2Department of Physics, Chung Yuan Christian University, Taoyuan, Taiwan
3Department of Physics, National Sun Yat-sen University, Kaohsiung, Taiwan
* Presenter:Tzu-Hung Chuang, email:chuang.th@nsrrc.org.tw
The photoelectron-related image and nano-spectroscopy (PRINS) end-station located at the Taiwan Photon Source (TPS) 27A2 houses a photoelectron momentum microscope (MM) capable of performing direct-space imaging, momentum-space imaging, and photoemission spectroscopy with position sensitivity [1-2]. Offline commissioning has been initiated from mid-2022 using two in-house photon sources, an Hg lamp and He(I) radiation. In this report, we demonstrate the performance of this microscope by measuring a standard checkerboard-patterned specimen and an Au(111) single crystal. By analyzing the intensity profile of the edge of the Au patterns, the Rashba-splitting of Au(111) Shockley surface state at 300 K, and the photoelectron intensity across the Fermi-edge at 80 K, the spatial, momentum, and energy resolution were estimated to be 50 nm, 0.0172 Å-1 and 26 meV, respectively [2].
Additionally, we demonstrate several examples of the investigation on two-dimensional (2D) transition metal dichalcogenides (TMDCs) taking advantage that the MM can directly access the electronic structures of 2D materials/heterostructures from μm-sized regions [3].
Finally, synchrotron soft X-rays are expected to arrive at the 27A2 end-station in the first half of 2025. Perspectives on future capabilities, including imaging based on X-ray photoelectron spectroscopy (XPS), X-ray absorption spectroscopy (XAS), and X-ray magnetic circular dichroism (XMCD) will be also discussed.

References:
[1] Shiu, et al., “When microscopy meets soft X-ray at TLS and TPS”, J. Electron Spectrosc. Relat. Phenom. 266, 147363 (2023).
[2] Chuang, et al., “Performance of a photoelectron momentum microscope in direct- and momentum-space imaging with ultraviolet photon source”, J. Synchrotron Rad. 31, 195 (2024).
[3] Chuang, et al., (in preparation)


Keywords: photoelectron momentum microscope, ARPES, PEEM, Fermi contour, XMCD