Ion Irradiation of Nanocrystalline Graphene on Quartz and Sapphire

TL;DR

This study investigates how Ga+ ion irradiation and annealing affect nanocrystalline graphene on quartz and sapphire, revealing its resilience to irradiation, potential for patterning, and ability to restore conductance after damage.

Contribution

It demonstrates the effects of ion irradiation and annealing on nanocrystalline graphene, including conductance retention, substrate adhesion enhancement, and nucleation promotion, enabling new patterning techniques.

Findings

Graphene remains conductive up to 3e14 cm-2 ion dose.

Annealing can fully restore conductance if dose is below 3e15 cm-2.

High doses cause sputtering and loss of graphene material.

Abstract

The effects of Ga+ ion irradiation and high temperature annealing on behavior of nanocrystalline graphene directly grown on quartz and sapphire are presented. It is shown that nanocrystalline graphene stands fairly high doses of ion irradiation (up to 3e14 cm-2 of 5 to 50 keV Ga+ ions) without degradation in conductance. At higher doses, nanocrystalline graphene rapidly loses its conductance and at doses over 2e15 cm-2 becomes actually insulating. Annealing in vacuum restores conductance of the irradiated nanocrystalline graphene and, if the irradiation has not exceeded a dose of 3e15 cm-2, this restoration can be complete. Ion irradiation at high doses approaching 1e16 cm-2 results in complete ion sputtering of a few layer graphene. Along with the irradiation-induced reduction of conductance and the temperature-induced restoration of conductance, two other effects of the ion irradiation are the enhancement of adhesion of graphene to substrate and the increase in the nucleation capability of substrate for direct deposition of graphene. For 50 keV Ga+ ions, the enhancement of adhesion is observed at irradiation doses over 2e14 cm-2. The promoted graphene nucleation is observed in a broad dose range. It is shown that the above effects can be used for development of methods of patterning of graphene on insulating substrates and a method of imprint lithography of graphene.