Local and Global Screening Properties of Graphene Revealed through Landau Level Spectroscopy

TL;DR

This study uses Landau-level spectroscopy to analyze how different substrates affect the electronic quality of graphene, revealing that intermediate layers and hBN significantly improve screening of potential fluctuations.

Contribution

It demonstrates that Landau-level spectroscopy can detect local and global potential fluctuations and shows that inserting intermediate graphene layers and hBN enhances substrate screening.

Findings

Intermediate graphene layers double the electronic mean free path.

hBN proximity suppresses global potential fluctuations.

High-quality graphene devices can be fabricated on SiO2 substrates.

Abstract

One-atom thick crystalline layers and their vertical heterostructures carry the promise of designer electronic materials that are unattainable by standard growth techniques. In order to realize their potential it is necessary to isolate them from environmental disturbances in particular those introduced by the substrate. But finding and characterizing suitable substrates, and minimizing the random potential fluctuations they introduce, has been a persistent challenge in this emerging field. Here we show that Landau-level (LL) spectroscopy is exquisitely sensitive to potential fluctuations on both local and global length scales. Harnessing this technique we demonstrate that the insertion of an intermediate graphene layer provides superior screening of substrate induced disturbances, more than doubling the electronic mean free path. Furthermore, we find that the proximity of hBN acts as a nano-scale vacuum cleaner, dramatically suppressing the global potential fluctuations. This makes it possible to fabricate high quality devices on standard SiO2 substrates.