Tuning the Band Gap in Silicene by Oxidation

TL;DR

This study demonstrates that the band gap of silicene monolayers on Ag(111) can be precisely tuned from semimetallic to semiconducting by controlling oxygen adatom adsorption, verified through microscopy, spectroscopy, and calculations.

Contribution

It reveals how oxygen adatoms and buckled structures influence band-gap engineering in silicene, providing a new method for electronic property control in 2D materials.

Findings

Oxygen adatoms can tune silicene's band gap.

Different buckled structures affect oxidation behavior.

Silicene retains structure under full oxygen coverage.

Abstract

Silicene monolayers grown on Ag(111) surfaces demonstrate a band gap that is tunable by oxygen adatoms from semimetallic to semiconducting type. By using low-temperature scanning tunneling microscopy, it is found that the adsorption configurations and amounts of oxygen adatoms on the silicene surface are critical for band-gap engineering, which is dominated by different buckled structures in R13xR13, 4x4, and 2R3x2R3 silicene layers. The Si-O-Si bonds are the most energy-favored species formed on R13xR13, 4x4, and 2R3x2R3 structures under oxidation, which is verified by in-situ Raman spectroscopy as well as first-principles calculations. The silicene monolayers retain their structures when fully covered by oxygen adatoms. Our work demonstrates the feasibility of tuning the band gap of silicene with oxygen adatoms, which, in turn, expands the base of available two-dimensional electronic materials for devices with properties that is hardly achieved with graphene oxide.