Defect Engineering in Two-dimensional Materials: Insight From Atomistic Simulations
Institute of Ion Beam Physics and Materials Research Helmholtz-Zentrum Dresden-Rossendorf
Local Project ID:
HPC Platform used:
Hazel Hen of HLRS
Beams of energetic ions are efficient tools to change the morphology and properties of both bulk and nanomaterials. In case of two-dimensional (2D) materials, the whole atomically thin structure of the material can easily be modified by ions, as ion ranges already at low energies are much greater than the sample thickness. In addition, the properties of 2D materials can be tailored by controllable introduction of defects, [1-3] which necessitates a full microscopic understanding of the response of 2D materials to ion irradiation.
Atomically thin membranes
Focused ion beams can be used to pattern 2D materials and ultimately to create arrays of nanoscale pores in atomically thin membranes for various technologies such as DNA sequencing, water purification and separation of chemical species. It is clear that precise control of pore sizes is essential for the effective use of 2D materials in these applications.
Among 2D materials, transition metal dichalcogenides (TMDs), and specifically, MoS2, are of particular interest due to their spectacular physical properties, which make them intriguing candidates for various electronic, optical and energy conversion applications.
We have systematically studied the response of MoS2 monolayer to cluster ion irradiation, by carrying out a series of large-scale molecular dynamics (MD) simulations. We focused on the production and characterization of defects in freestanding and supported monolayers under noble gas cluster irradiation with incident ion energies varied from 1 eV/atom to 1000 eV/atom.
The results showed that cluster irradiation can produce uniform holes in MoS2 sheets with the diameter being dependent on cluster size and energy. Energetic clusters with grazing incident angles can displace sulfur atoms preferentially from either top or bottom layers of S atoms in MoS2 and also clean the surface of MoS2 sheets from adsorbents. The presence of substrate in supported monolayer has a significant influence on the defect production and therefore pore creation in both low and high cluster energies. In a high energy regime, the combined effects from the direct collision and indirect impact from the substrate enhance the damage in 2D materials, while at low energy regimes substrate hinder the defect production by absorbing the shock transferred from the incident impacts. Our findings suggest new opportunities for the creation of 2D nanoporous membranes using cluster beam engineering of TMDs.
Controlled doping for optoelectronics
The efficient integration of TMDs into the current electronic device technology requires effective modulation of their optoelectronic properties which can be achieved via controllable doping. We further studied the possibility of direct doping of Cl atoms in few-layer MoSe2 lattice via low-energy ion implantation. Our density functional theory calculations and experimental temperature-dependent micro-Raman spectroscopy data indicates that Cl atoms are incorporated into the atomic network of MoSe2 as substitutional donor impurities. This non-chemical doping method can be an alternative to complex chemical doping process which often suffer from poor doping site selectivity, adsorption contamination from different chemical residuals, and secondary impurities.
Our theoretical results provided support to the ongoing fundamental experimental studies on ion irradiation of 2D materials in the context of their future applications in electronic and optical and energy storage devices. None of these calculations would have been possible without computational resources provided through PRACE, as such calculations typically include a very large number of atoms which computationally very expensive, and require massive parallel architecture.
“Defects in materials are not always harmful but they may bring new features or even useful functionalities if we know how to create them in a controlled way!”
Publications as an outcome of the HPC projects
 T. Joseph, M. Ghorbani-Asl, A. Kvashnin, K. Larionov, Z. Popov, P. Sorokin, and A.V. Krasheninnikov, Non-stoichiometric phases of two-dimensional transition-metal dichalcogenides: from chalcogen vacancies to pure metal membranes, J. Phys. Chem. Lett. 10, 6492 (2019).
 P. Valerius, S. Kretschmer, B. Senkovskiy, S. Wu, J. Hall, A. Herman, N. Ehlen, M. Ghorbani-Asl, A. Gruuneis, A.V. Krasheninnikov, T. Michely, Reversible crystalline-to-amorphous phase transformations in monolayer MoS2 under grazing ion irradiation, 2D Mater. 7, 025005 (2020).
 B. Mohanty, Y. Wei, M. Ghorbani-Asl, A.V. Krasheninnikov, P. Rajput, B. K. Jena, Revealing the defect-dominated oxygen evolution activity of hematene, J. Mater. Chem. A 8, 6709 (2020).
 S. Ghaderzadeh, V. Ladygin, M. Ghorbani-Asl, G. Hlawacek, and A.V. Krasheninnikov, MoS2 monolayers under cluster ion irradiation: a molecular dynamics study, ACS Appl. Mater. Inter. 12, 37454 (2020).
 S. Prucnal, A. Hashemi, M. Ghorbani-Asl, R. Hübner, J. Duan, D. Sharma, D.R.T Zahn, R. Ziegenrücker, Y. Wei, U. Kentsch, A. V. Krasheninnikov, M. Helm and S. Zhou, Chlorine doping of MoSe2 flakes by ion implantation, Nanoscale 13, 5834 (2021).
M.Sc. Sadegh Ghaderzadeh, M.Sc. Thomas Joseph, M. Sc. Sayedarsalan Hashemipetrudi, Dr. Silvan Kretschmer, Dr. Ilia Chepkasov, Dr. Arkady Krasheninnikov, Dr. Mahdi Ghorbani-Asl
Helmholtz-Zentrum Dresden-Rossendorf, Germany
Dr. Mahdi Ghorbani-Asl
Institute of Ion Beam Physics and Materials Research
D-01328 Dresden (Germany)
e-mail: mahdi.ghorbani [@] hzdr.de
NOTE: This simulation project was made possible by PRACE (Partnership for Advanced Computing in Europe) allocating a computing time grant on GCS HPC system Hawk of the High-Performance Computing Center Stuttgart (HLRS). GCS is a hosting member of PRACE.
Local project ID:PP18184458