Ordered Array of Single Adatoms with Remarkable Thermal Stability: Au/Fe3O4(001)

TL;DR

This study demonstrates that gold adatoms on Fe3O4(001) form a highly stable, ordered array at specific sites, maintaining their position even after high-temperature annealing, making it a promising model for single-atom reactivity studies.

Contribution

The paper reveals that Au adatoms preferentially adsorb at narrow sites on Fe3O4(001) and remain stable up to 400°C, highlighting a novel, thermally stable single-atom configuration.

Findings

Au adatoms occupy narrow sites exclusively

Adatoms show no sintering up to 400°C

Site preference linked to charge and orbital ordering

Abstract

Gold deposited on the Fe$_3$O$_4$(001) surface at room temperature was studied using Scanning Tunneling Microscopy (STM) and X-ray photoelectron spectroscopy (XPS). This surface forms a ($\sqrt2 \times \sqrt2$)R45$^{\circ}$ reconstruction, where pairs of Fe and neighboring O ions are slightly displaced laterally producing undulating rows with `narrow' and `wide' hollow sites. At low coverages, single Au adatoms adsorb exclusively at the narrow sites, with no significant sintering up to annealing temperatures of 400 $^{\circ}$C. We propose the strong site preference to be related to charge and orbital ordering within the first subsurface layer of Fe$_3$O$_4$(001)-($\sqrt2 \times \sqrt2$)R45$^{\circ}$. Due to its high thermal stability, this could prove an ideal model system for probing the chemical reactivity of single atomic species.