# Nonparametric Modeling of Face-Centered Cubic Metal Photocathodes

## TL;DR

This paper applies a nonparametric photoemission model to analyze FCC metal photocathodes, focusing on their surface states and optical properties, with implications for generating hollow cone illumination.

## Contribution

It introduces a nonparametric modeling approach to FCC metal photocathodes and evaluates surface state effects using DFT, expanding understanding of photoemission mechanisms.

## Key findings

- Surface state photoemission observed on (111) surfaces.
- DFT evaluation confirms potential for hollow cone illumination.
- Analysis includes both noble and p-block FCC metals.

## Abstract

Face-centered cubic (FCC) is an important crystal structure, and there are ten elemental FCC metals (Al, Ag, Au, Ca, Cu, Pb, Pd, Pt, Rh, and Sr) that have this structure. Three of them could be used as photocathodes (Au, Rh, Pt, and Pd have very high work functions; Ca and Sr are very reactive). Au has high work function, but it is included for the sake of the completeness of noble metals' photoemission investigation. In this paper, we will apply the nonparametric photoemission model to investigate these four remaining FCC photocathodes; two noble metals (Cu and Au), two p-block metals (Al and Pb). Apart from the fact that the direct photoemission is dominant for most FCC photocathodes, photoemission from a surface state has also been observed for the (111)-face of noble metals. The optical properties of the (111) surface state will be extensively reviewed both experimentally and theoretically, and a surface state DFT evaluation will be performed to show that the photocathode generated hollow cone illumination (HCI) can be realized.