Combined AFM and STM measurements of a silicene sheet grown on Ag(111) surface

TL;DR

This study combines nc-AFM and STM techniques to analyze silicene on Ag(111), revealing atomic-scale buckling and structural details of the surface superstructures.

Contribution

First combined nc-AFM and STM measurements of silicene on Ag(111), providing new insights into its atomic structure and buckling behavior.

Findings

Identified (sqrt13x sqrt13)R13.9° and (4x4) superstructures

Observed contrast inversion in nc-AFM topography at close distances

Confirmed strong buckling of the silicene honeycomb layer

Abstract

In this Letter, we present the first non-contact atomic force microscopy (nc-AFM) of a silicene on silver (Ag) surface, obtained by combining non-contact atomic force microscopy (nc-AFM) and scanning tunneling microscopy (STM). STM images over large areas of silicene grown on Ag(111) surface show both (sqrt13xsqrt13)R13.9{\deg} and (4x4) superstructures. For the widely observed (4x4) structure, the nc-AFM topography shows an atomic-scale contrast inversion as the tip-surface distance is decreased. At the shortest tip-surface distance, the nc-AFM topography is very similar to the STM one. The observed structure in the nc-AFM topography is compatible with only one out of two silicon atoms being visible. This indicates unambiguously a strong buckling of the silicene honeycomb layer.