Atomic understanding of structural deformations upon ablation of graphene

Abstract

We investigate the atomic rearrangement in graphene under femtosecond pulse illumination with reactive molecular dynamics simulations and compare with ultra-fast laser ablation experiments. To model the impact of the laser pulse irradiation, heat is locally applied to a selected area of the graphene layer and the resulting structural deformation is simulated as a function of time, providing a detailed understanding of the bond breaking process under laser illumination and subsequent re-equilibration after the pulse is turned off. Analysis of the atomic dynamics indicates that the types of defects formed depend on the pulse energy and exposure duration. By varying the exposed area, we determine that the shape of the ablated area is not only a function of the pulse energy, but also of the beam spot size and pulse repetition. Furthermore, we apply a machine learning approach to extrapolate our simulated data to experimental length scales and reproduce the trends in ablated area as a function of temperature. Our study provides a first step towards understanding the design parameters for graphene nano-patterning.

Nanoprocessing of Self-Suspended Monolayer Graphene and Defect Formation by Femtosecond-Laser Irradiation

“…The threshold fluence of ∼10 mJ/cm 2 for the defect formation was in agreement with that predicted by a numerical simulation and with the most recent experimental results of nanopore formation, despite the differences in laser system conditions. Based on the findings of this work, a series of machining processes can be inferred, in which the repeated laser irradiation increased the defect density, eventually forming many nanopores and finally creating a hole with a diameter of ∼100 nm.…”

“…Recently, Alaghemandi et al simulated the atomic dynamics in graphene under femtosecond-laser irradiation and demonstrated the formation of atomic-level defects as well as nanopores . Atomic defects in the crystal structure of graphene enhance chemical reactivity and can be utilized to locally functionalize graphene membranes by attaching arbitrary chemical groups to the defect vacancy. , The defects also affect the electronic structure of graphene and thus have potential applications in high-performance electronics materials and in innovative technologies such as valleytronics. , In a very recent study, large numbers of nanopores were generated in monolayer graphene on a Si/SiO 2 wafer using a high-repetition-rate femtosecond-laser irradiation .…”

Effect of Hyperthermal Hybrid Gas Composition on the Interfacial Oxidation and Nitridation Mechanisms of Graphene Sheet

“…The RMD simulations proposed in this work are all based on the open-source LAMMPS MD simulator by using the reactive force field ReaxFF C/H/O/N . , The validity of ReaxFF C/H/O/N is demonstrated by simulating combustion between hydrocarbon/O 2 mixtures and then further applied to investigate the ablation of graphene under femtosecond pulse illumination successfully . The overall system energy by ReaxFF can be divided into various partial energy contributions as follows: − E system = E bond + E over + E val + E pen + E tors + E conj + E vdWaals + E coulombic where E system is the energy of the overall system, E bond is the bond energy, E over is the overcoordination energy, E under is the undercoordinated energy, E val is the valence angle energy, E pen is the penalty energy, E tor is the torsion energy, E conj is the conjugation energy, E vdWaals is the van der Waals interactions energy, and E Coulombic is the Coulombic interactions energy.…”

“…44,45 The validity of ReaxFF C/H/O/N 35 is demonstrated by simulating combustion between hydrocarbon/ O 2 mixtures and then further applied to investigate the ablation of graphene under femtosecond pulse illumination successfully. 46 The overall system energy by ReaxFF can be divided into various partial energy contributions as follows: 47…”

“…To extend classical MD simulations for elucidating the chemical reaction mechanisms, an empirical reactive force field (ReaxFF) was proposed by Van Duin et al, , also termed the reactive molecular dynamics (RMD) simulation method. Pioneering RMD works have been conducted to investigate the ablation mechanism of graphene. − For instance, Goverapet Srinivasan et al investigated the size and multilayer structure effects of graphene sheet on the thermal reaction of atomic oxygen (AO). The results showed that the recombination of AO on the surface of the graphene sheet occurred predominantly through the Eley–Rideal (E–R)-type reaction mechanism.…”