# Localized segregation of gold in ultra-thin Fe films on Au(001)

## TL;DR

This study investigates how gold segregates in ultra-thin iron films on gold surfaces during growth and annealing, revealing localized segregation mechanisms and the importance of spatially-resolved analysis.

## Contribution

It uncovers the localized gold segregation process in Fe films on Au(001) and highlights the role of annealing and oblique deposition geometry in this phenomenon.

## Key findings

- Au segregates to the Fe surface during growth.
- Annealing at 190°C induces crack formation facilitating Au diffusion.
- Localized segregation is influenced by shadowing effects.

## Abstract

The growth of up to 10 monolayer-thick Fe films on a Au(001) surface was investigated during deposition at room temperature and during annealing using low-energy electron diffraction and x-ray photoemission spectroscopy as well as locally with low-energy electron microscopy and photoemission electron microscopy. The growth proceeds with a submonolayer of Au segregating to the surface of Fe, which is in agreement with previous studies. Annealing was found to be critical for the presence of Au on the Fe surface. Our findings show that Au segregation proceeds by the formation of cracks in the Fe film, starting at the annealing temperature of 190 {\deg}C, through which Au diffuses towards the surface. We explain the localized Au segregation with a shadowing effect due to the oblique deposition geometry. As a result, an Fe film with significantly improved roughness, but covered with a Au overlayer, is obtained. This study shows the necessity to employ spatially-resolved techniques to fully understand the growth modes of the layered epitaxial systems.