Work function seen with sub-meV precision through laser photoemission

TL;DR

This study demonstrates that laser-based angle-resolved photoemission spectroscopy (ARPES) can measure the work function of surfaces with five significant digits, surpassing traditional methods in precision.

Contribution

The paper introduces a laser-ARPES method capable of determining the work function with five significant digits, enabling highly precise surface electronic property measurements.

Findings

Achieved sub-meV precision in work function measurement.

Resolved work function changes due to surface aging.

Demonstrated stability of measurements across temperature range.

Abstract

Electron emission can be utilised to measure the work function of the surface. However, the number of significant digits in the values obtained through thermionic-, field- and photo-emission techniques is typically just two or three. Here, we show that the number can go up to five when angle-resolved photoemission spectroscopy (ARPES) is applied. This owes to the capability of ARPES to detect the slowest photoelectrons that are directed only along the surface normal. By using a laser-based source, we optimised our setup for the slow photoelectrons and resolved the slowest-end cutoff of Au(111) with the sharpness not deteriorated by the bandwidth of light nor by Fermi-Dirac distribution. The work function was leveled within $\pm$0.4 meV at least from 30 to 90 K and the surface aging was discerned as a meV shift of the work function. Our study opens the investigations into the fifth significant digit of the work function.