Micro-Structuring, Ablation and Defect Generation in Graphene with Femtosecond Pulses

TL;DR

This paper investigates how femtosecond laser pulses can precisely modify or ablate single-layer graphene, revealing thresholds and defect structures that enable micro- and nano-scale patterning for advanced device fabrication.

Contribution

It demonstrates controlled ablation and defect generation in graphene using femtosecond pulses, providing insights into laser parameters for tailored material modifications.

Findings

Low ablation threshold of ~9.2 mJ/cm2 for graphene.

Defect regions extend ~2 um from ablated edges with defect spacing ~58 nm.

Modification at 75% of threshold maintains structure while introducing nanoscale defects.

Abstract

Femtosecond micromachining offers a contact-free and mask-less technique for material patterning. With ultrafast laser irradiation, permanent modifications to the properties of single layer graphene through material ablation or defect introduction can be induced. Multiple femtosecond pulse interactions with a single layer graphene are studied and a low laser ablation threshold ~9.2 mJ/cm2 is reported for a 15 second illumination time. Clean ablated structures are generated in such a multi pulse irradiation configuration at low pulse energies as an attractive alternative to ablation with single femtosecond, high energy pulses. For a fully ablated graphene hole, a radially symmetric region extending around 2 um from the ablated edge is characterized by strong defect generation. Average distances between point-defects down to ~58 nm are derived and Raman spectroscopy implies that overall there is a strong resemblance to amorphous structures. For fluence values around 75% of the ablation threshold, modification with defect generation down to ~48 nm average defects lengths is reported, while the underlying graphene structure is maintained. Thus, depending on the laser parameter choice, the same laser configuration can be used to ablate graphene or to primarily introduce defect states. The presented findings offer interesting insights into femtosecond induced structural modifications of graphene that can lead to improved precision ablation and patterning of single-layer materials at the micro- and nano-scale. Further, this can be attractive for graphene or carbon-based device fabrication as well as sensor and transistor applications, where regions of varying carrier concentrations and different electrical, optical or physical properties are desired.