Characterization of electronic structure of periodically strained graphene

TL;DR

This study investigates how periodic biaxial tensile strain affects the electronic structure of graphene, revealing increased work function and density of states, with implications for electronic property tuning.

Contribution

It provides the first detailed characterization of the electronic structure changes in graphene induced by periodic biaxial strain using multiple spectroscopic techniques.

Findings

Strain ranges from 0.4% to 0.7% in graphene.

Strained graphene exhibits higher work function.

Electronic density of states increases with strain.

Abstract

We induced periodic biaxial tensile strain in polycrystalline graphene by wrapping it over a substrate with repeating pillar-like structures with a periodicity of 600 nm. Using Raman spectroscopy, we determined to have introduced biaxial strains in graphene in the range of 0.4% to 0.7%. Its band structure was characterized using photoemission from valance bands, shifts in the secondary electron emission, and x-ray absorption from the carbon 1s levels to the unoccupied graphene conduction bands. It was observed that relative to unstrained graphene, strained graphene had a higher work function and higher density of states in the valence and conduction bands. We measured the conductivity of the strained and unstrained graphene in response to a gate voltage and correlated the changes in their behavior to the changes in the electronic structure. From these sets of data, we propose a simple band diagram representing graphene with periodic biaxial strain.