Thermal stability study of nitrogen functionalities in a graphene network

TL;DR

This study investigates the thermal stability of nitrogen functionalities in graphene nanoflakes, revealing how nitrogen configurations evolve with temperature and enabling controlled doping for device applications.

Contribution

It demonstrates the use of low energy N+ ion bombardment to achieve high nitrogen doping levels and tracks the temperature-dependent evolution of nitrogen configurations in graphene.

Findings

Nitrogen doping levels reach up to 9.6 at.%

Pyridinic nitrogen dominates at room temperature

Graphitic nitrogen becomes prevalent at 800°C

Abstract

Catalyst-free vertically aligned graphene nanoflakes possessing a large amount of high density edge planes were functionalized using nitrogen species in a low energy N+ ion bombardment process to achieve pyridinic, cyanide and nitrogen substitution in hexagonal graphitic coordinated units. The evolution of the electronic structure of the functionalized graphene nanoflakes over the temperature range 20-800^{\circ}C was investigated in situ, using high resolution x-ray photoemission spectroscopy. We demonstrate that low energy irradiation is a useful tool for achieving nitrogen doping levels up to 9.6 at.%. Pyridinic configurations are found to be predominant at room temperature, while at 800^{\circ}C graphitic nitrogen configurations become the dominant ones. The findings have helped to provide an understanding of the thermal stability of nitrogen functionalities in graphene, and offer prospects for controllable tuning of nitrogen doping in device applications.