# Electron doping of exfoliated multilayer graphene induced by dissociative H2 adsorption due to long-term exposure to 80-bar H2 gas

## TL;DR

Exposing multilayer graphene to high-pressure hydrogen gas causes electron doping, changing its electronic properties in a simple and chemical-free way.

## Contribution

A novel method for electron doping of multilayer graphene using dissociative hydrogen adsorption under high pressure is demonstrated.

## Key findings

- Long-term exposure to 80 bar H2 induces electron doping in multilayer graphene.
- Dissociative H2 adsorption leads to structural changes like increased C‒H bonding.
- Molecular dynamics simulations confirm electron doping at surface layers and defects.

## Abstract

Semiconducting graphene is expected to replace silicon in the electronics industry, and various methods have been proposed for this purpose. In this study, we demonstrate that the long-term exposure of multilayer graphene to 80 bar of molecular hydrogen induces electron doping in graphene. Ambipolarity behavior disappeared, and the current in the transfer curves decreased and increased in the negative gate voltage (Vg) and positive Vg regions, respectively. The charge neutrality point shifted from 4.18 to over −80 V. Two resonant scatterings due to hydrogen adatoms were observed in the temperature-dependent transfer curves. For multilayer graphene with a boundary (edge), different behavior was observed in the transfer characteristics. Upon exposure to 80 bar of H2 pressure, the drain current of the time-dependent transfer curve rapidly decreased; however, it increased in the positive Vg region after 60 h of exposure to H2. Structural changes, particularly an increase in C‒H bonding, were observed using various characterization methods. These results were interpreted by the dissociative H2 adsorption of graphene. Molecular dynamics simulations also revealed the presence of electron doping due to dissociative adsorption. Furthermore, the simulations confirmed that dissociative adsorption occurred on the surface layer and at vacancies and defects.

This study demonstrates significant electron doping in multilayer graphene through prolonged exposure to highpressure hydrogen gas, revealing a straightforward method for modifying its electronic properties without harmful chemicals.