Atomic and mesoscopic structure of Dy-based surface alloys on noble metals

TL;DR

This study investigates the atomic and mesoscopic structures of Dy-based surface alloys on noble metals, revealing diverse superstructures and strain-relief mechanisms, highlighting surface alloying as a tool to tailor nanoscale material properties.

Contribution

It provides detailed atomic and mesoscopic structural analysis of Dy-based surface alloys on noble metals using STM and LEED, uncovering new superstructures and strain-relief features.

Findings

Homogeneous moiré patterns in DyCu2/Cu(111) and DyAu2/Au(111) surface alloys.

Inhomogeneous structure with domain walls in DyAg2/Ag(111).

Surface alloying can tailor local atomic and mesoscopic structures.

Abstract

Surface alloys are a highly tunable class of low dimensional materials with the opportunity to tune and control the spin and charge carrier functionalities on the nanoscale. Here, we focus on the atomic and mesoscopic structural details of three distinctive binary rare-earth-noble metals (RE/NM) surface alloys by employing scanning tunneling microscopy (STM) and low energy electron diffraction (LEED). Using Dysprosium as the guest element on fcc(111) noble metal substrates, we identify the formation of non-commensurate surface alloy superstructures which exhibit homogeneous moir\'e patterns for DyCu2/Cu (111) and DyAu2/Au(111), while an inhomogeneous one is found for DyAg2/Ag(111). The variations in the local structure are analyzed for all three surface alloys and the observed differences are discussed in the light of the lattice mismatches of the alloy layer with respect to the underlying substrate. For the particularly intriguing case of a Dy-Ag surface alloy, the surface alloy layer does not show a uniform long-range periodic structure, but consists of local hexagonal tiles separated by extended domain walls. These domain walls exist to relief the in-plane strain within the DyAg2 surface alloy layer. Our findings clearly demonstrate that surface alloying is an intriguing tool to tailor both the local atomic, but also the mesoscopic moir\'e structures of metallic heterostructures.