# STM/S study of electronic inhomogeneity evolution with gate voltage in graphene: role of screening and charge-state of interface defects

## TL;DR

This study investigates how electronic inhomogeneities in graphene evolve with gate voltage, revealing the role of interface defect charge states and screening effects, which are crucial for future memory device applications.

## Contribution

It provides experimental evidence linking charge-state changes of interface defects to inhomogeneity evolution in graphene, supported by STM/STS data and screening theory.

## Key findings

- Reversal of local contrast near Dirac point
- Sharp change in correlation length scales
- Agreement with screening theory predictions

## Abstract

Evolution of electronic inhomogeneities with back-gate voltage in graphene on SiO$_2$ was studied using room temperature scanning tunneling microscopy and spectroscopy. The reversal of local contrast in some places in the STS maps and sharp changes in cross-correlations between topographic and conductance maps, when graphene Fermi energy approaches its Dirac point, are attributed to change in charge-state of interface defects. The spatial correlations in the conductance maps, described by two different length scales and their growth during approach to Dirac point, show a qualitative agreement with the predictions of the screening theory of graphene. Thus a sharp change in the two length-scales close to the Dirac point, seen in our experiments, is interpreted in terms of the change in charge state of some of the interface defects. A systematic understanding and control of the charge state of defects will help in memory applications of graphene.