Structure Determination of Disordered Metallic Sub-Monolayers by Helium Scattering: A Theoretical and Experimental Study

TL;DR

This study combines theoretical and experimental helium scattering techniques to determine the atomic structure of disordered silver sub-monolayers on platinum, revealing compact clusters with specific size and shape characteristics.

Contribution

It introduces a novel approach integrating quantum scattering calculations with He scattering data to model disordered metallic surface structures at atomic resolution.

Findings

Clusters are narrowly size-dispersed and compact

Clusters have up to two layers with few defects

He scattering effectively reveals complex surface phases

Abstract

An approach based on He scattering is used to develop an atomic-level structural model for an epitaxially grown disordered sub-monolayer of Ag on Pt(111) at 38K. Quantum scattering calculations are used to fit structural models to the measured angular intensity distribution of He atoms scattered from this system. The structure obtained corresponds to narrowly size-dispersed compact clusters with modest translational disorder, and not to fractals which might be expected due to the low surface temperature. The clusters have up to two layers in height, the lower one having few defects only. The relations between specific features of the angular scattering distribution, and properties such as the cluster sizes and shapes, the inter-cluster distance distribution etc., are discussed. The results demonstrate the usefulness of He scattering as a tool for unraveling new complex surface phases.