Contrast Inversion of Photoelectron Spectro-microscopy Image

Abstract

The contrast of a photoelectron microscopy image depends on the type of excitation photon source and the photoelectron kinetic energy. The contrast inversion observed in the photoelectron image by Hg lamp excitation is due to differences in work functions specific to materials and surface conditions, and the contrast inversion in the case of vacuum ultraviolet light excitation is due to the difference in the valence band density of states. The mechanism of contrast formation in valence photoelectron images is well understood qualitatively as described above, but quantitative evaluations are required for accurate understanding. We investigated the photoelectron image contrast of gold checkerboard pattern printed on the silicon wafer. The intensity of the gold region near the Fermi level is higher than that of the silicon substrate region, while the inverted contrast images were obtained at lower kinetic energies. We found that in the case of core and valence photoelectrons, certain contamination degrades the image quality, but in the case of Hg lamp excitation, it increases signal intensity owing to the lowering of work function.

Characterization of epitaxial CVD graphene on Ir(111)/α-Al2O3(0001) by photoelectron momentum microscopy

“…The electronic structures of graphene grown on Ir(111)/α-Al 2 O 3 (0001) near the Fermi level were determined by valence band photoelectron spectroscopy (VB-PES) using PMM (SPECS KREIOS 150MM) at the linearly polarized soft X-ray beamline BL6U of the UVSOR-III synchrotron. 23,24) The photon energy was varied from 50 to 120 eV. The X-ray absorption near-edge structure (XANES) of graphene grown on Ir(111)/α-Al 2 O 3 (0001) was acquired by the Auger electron yield method using PMM.…”

“…In recent years, the crystal structure of graphene has been characterized by transmission electron microscopy, 20) scanning tunneling microscopy, 21,22) and low energy electron diffraction. 22) In this study, we focus on photoelectron momentum microscopy 23,24) for characterization of the single-crystallinity of graphene. The photoelectron momentum microscope (PMM) consists of a momentum microscope and a soft X-ray synchrotron radiation source.…”

Prospects required for future light-source facilities: a case of UVSOR synchrotron facility

“…In FY2020, we started the development of imaging for photoelectron spectroscopy. We are currently working on a project to fully evaluate electronic states by spin-resolved photoelectron momentum microscope with SR excitation [16][17][18][19][20][21][22][23][24][25][26][27], which will be a pioneer project of its kind in Japan. It is expected that multimodal measurements in complex systems will lead to a new landscape of materials science.…”

Development of dual-beamline photoelectron momentum microscopy for valence orbital analysis

“…Scanning photon energy over certain absorption edges is called XAS-PEEM, and scanning kinetic energy over various electron core levels is called XPEEM. These approaches facilitate the spatial mapping of elements and are regarded as 'spectro-microscopy' (Locatelli & Mentes ¸, 2015;Makita et al, 2021).…”