Abstract
Deployments of spherical grids to obtain high energy and angular resolutions for retarding field analyzers (RFAs) having acceptance angles as large as or larger than ±45° were explored under the condition of using commercially available microchannel plates with effective diameters of approximately 100 mm. As a result of electron trajectory simulations, a deployment of three spherical grids with significantly different grid separations instead of conventional equidistant separations showed an energy resolving power (E/ΔE) of 3200 and an angular resolution of 0.6°. The mesh number of the wire mesh retarding grid used for the simulation was 250. An RFA constructed with the simulated design experimentally showed an E/ΔE of 1100 and an angular resolution of 1°. Using the RFA and synchrotron radiation of 900 eV, photoelectron diffraction (PED) measurements were performed for single-crystal graphite. A clear C 1s PED pattern was observed even when the differential energy of the RFA was set at 0.5 eV. Further improvement of the energy resolution was theoretically examined under the assumption of utilizing a retarding grid fabricated by making a large number of radially directed cylindrical holes through a partial spherical shell instead of using a wire mesh retarding grid. An E/ΔE of 14 500 was predicted for a hole design with a diameter of 60 μm and a depth of 100 μm. A retarding grid with this hole design and a holed area corresponding to an acceptance angle of ±7° was fabricated. An RFA constructed with this retarding grid experimentally showed an E/ΔE of 1800. Possible reasons for the experimental E/ΔE lower than the theoretical values are discussed.
Highlights
Photoelectron diffraction (PED) is a powerful method for studying the local atomic arrangements of surface structures.1–4 photoelectron diffraction (PED) patterns can be used for real-space atomic imaging called photoelectron holography (PEH).5–8 An advantage of PED or PEH is the utilization of chemical shifts in core-level photoemission spectra
Deployments of spherical grids to obtain high energy and angular resolutions for retarding field analyzers (RFAs) having acceptance angles as large as or larger than ±45◦ were explored under the condition of using commercially available microchannel plates with effective diameters of approximately 100 mm
We report a method for obtaining energy resolving powers of 1000 or higher and angular resolutions of 1◦ or smaller for 3-grid spherical RFAs that have acceptance angles as large as or larger than ±45◦
Summary
Photoelectron diffraction (PED) is a powerful method for studying the local atomic arrangements of surface structures. PED patterns can be used for real-space atomic imaging called photoelectron holography (PEH). An advantage of PED or PEH is the utilization of chemical shifts in core-level photoemission spectra. PED patterns can be used for real-space atomic imaging called photoelectron holography (PEH).. An advantage of PED or PEH is the utilization of chemical shifts in core-level photoemission spectra. This enables one to specify chemically different atomic sites of the same element. PED pattern measurements with such high-energy resolutions have only been performable through time-consuming angular scans of samples using non-displaytype analyzers such as concentric hemispherical analyzers (CHAs). For this reason, high-energy-resolution display-type photoelectron analyzers are desired
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