Impact of thermal annealing on graphene devices encapsulated in hexagonal boron nitride

TL;DR

This study investigates how thermal annealing affects the uniformity and properties of graphene encapsulated in hexagonal boron nitride, revealing improved homogeneity without altering key material characteristics.

Contribution

It provides detailed insights into the effects of annealing on encapsulated graphene, especially regarding doping, strain, and Raman spectral features, which were previously not well understood.

Findings

Annealing reduces doping and strain variations, leading to more homogeneous samples.

Material properties like mobility and overall doping are unaffected by annealing.

Raman spectroscopy reveals strain and doping information through 2D-peak and G-peak correlation.

Abstract

We present a thermal annealing study on single-layer and bilayer (BLG) graphene encapsulated in hexagonal boron nitride. The samples are characterized by electron transport and Raman spectroscopy measurements before and after each annealing step. While extracted material properties such as charge carrier mobility, overall doping, and strain are not influenced by the annealing, an initial annealing step lowers doping and strain variations and thus results in a more homogeneous sample. Additionally, the narrow 2D-sub-peak widths of the Raman spectrum of BLG, allow us to extract information about strain and doping values from the correlation of the 2D-peak and the G-peak positions.