# Probing the Shape of a Graphene Nanobubble

## TL;DR

This paper investigates the shape, pressure, and properties of graphene nanobubbles using numerical simulations and experimental techniques, revealing universal shape behavior and potential for strain engineering.

## Contribution

It introduces a simple elastic and adhesion model to predict nanobubble shape and pressure, linking vibrational density of states to bubble characteristics.

## Key findings

- Van der Waals pressure around 1 GPa for 10 nm bubbles
- Universal shape behavior of nanobubbles regardless of size
- Strain variation enables control of electronic and optical properties

## Abstract

Gas molecules trapped between graphene and various substrates in the form of bubbles are observed experimentally. The study of these bubbles is useful in determining the elastic and mechanical properties of graphene, adhesion energy between graphene and substrate, and manipulating the electronic properties via strain engineering. In our numerical simulations, we use a simple description of elastic potential and adhesion energy to show that for small gas bubbles ($\sim 10$ nm) the van der Waals pressure is in the order of 1 GPa. These bubbles show universal shape behavior irrespective of their size, as observed in recent experiments. With our results the shape and volume of the trapped gas can be determined via the vibrational density of states (VDOS) using experimental techniques such as inelastic tunneling and inelastic neutron scattering. The elastic energy distribution in the graphene layer which traps the nanobubble is homogeneous apart from its edge, but the strain depends on the bubble size thus variation in bubble size allows control of the electronic and optical properties.