111-1 SEMINAR 莊子弘(同步輻射)-1111026

Time:1111026 (Wed.) 14:20~16:20
Speaker:Prof.莊子弘(Tzu-Hung Chuang ) 國家同步輻射研究中心奈米科學小組/Nano Science Group, National Synchrotron Radiation Research Center
Title:Recent advances in spin-polarized X-ray momentum microscopy at the Taiwan Photon Source
The Photoelectron Related Image and Nano-Spectroscopy (PRINS) end-station at the Taiwan Photon Source (TPS) 27A2 will host a momentum microscope that aims to work on photoelectron-related imaging and nano-scale spectroscopy through the combination of an imaging-type electron column integrated with a hemispherical electron energy analyzer and an imaging spin filter. The microscope is able to conduct full-field imaging by collecting photoelectrons in either real-space or momentum-space with spin contrast. The main microscope system was delivered at the TPS at the end of 2021, and its on-site testing has been initiated in the first half of 2022. Although the beamline will not be ready until early 2023, the off-line commissioning by He-I radiation and a Hg lamp have delivered preliminary results in real-space, momentum-space, and spin-resolved imaging.
In this report, a real-space imaging on a standard checkerboard sample (Au/Si) with different field of views (FoV) illuminated by a Hg lamp is presented. A spatial resolution with less than 50 nm has been achieved. Then a series of momentum space images when sweeping the electron kinetic energies from Au(111) single crystal was obtained by He-I radiation, then a 3-dimensional dataset [I(kx, ky, EKE)] was then constructed. The Shockley surface state is clearly visible. The angle-resolved photoemission electron spectra can be obtained by slicing the 3-dimensional dataset along high symmetry directions. The energy resolution of less than 30 meV has been also achieved. Spin-resolved images can be obtained after introducing an imaging spin filter, which is based on the spin-dependent low energy electron scattering on a clean Ir(100) surface. A spin-polarized band structure on Au(111) can be identified through the contrast difference between two k-space images with different spin directions or scattering energies.
Place:S101, Gongguan Campus, NTNU
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