Ab initio molecular dynamics of atomic-scale surface reactions: insights into metal organic chemical vapor deposition of AlN on graphene

Abstract

Metal organic chemical vapor deposition (MOCVD) of group III nitrides on graphene heterostructures offers new opportunities for the development of flexible optoelectronic devices and for the stabilization of conceptually-new two-dimensional materials. However, the MOCVD of group III nitrides is regulated by an intricate interplay of gas-phase and surface reactions that are beyond the resolution of experimental techniques. We use density-functional ab initio molecular dynamics (AIMD) with van der Waals corrections to identify atomistic pathways and associated electronic mechanisms driving precursor/surface reactions during metal organic vapor phase epitaxy at elevated temperatures of aluminum nitride on graphene, considered here as model case study. The results presented provide plausible interpretations of atomistic and electronic processes responsible for delivery of Al, C adatoms, and C-Al, CH, AlNH admolecules on pristine graphene via precursor/surface reactions. In addition, the simulations reveal C adatom permeation across defect-free graphene, as well as exchange of C monomers with graphene carbon atoms, for which we obtain rates of ∼0.3 THz at typical experimental temperatures (1500 K), and extract activation energies E = 0.28 ± 0.13 eV and attempt frequencies A = 2.1 (×1.7) THz via Arrhenius linear regression. The results demonstrate that AIMD simulations enable understanding complex precursor/surface reaction mechanisms, and thus propose AIMD to become an indispensable routine prediction-tool toward more effective exploitation of chemical precursors and better control of MOCVD processes during synthesis of functional materials.

Nanoscale phenomena ruling deposition and intercalation of AlN at the graphene/SiC interface

“…Advantageous to the conceptual understanding of dissociative chemisorption and intercalation phenomena under MOCVD conditions in general, our recent AIMD study reveals atomistic and electronic processes responsible for delivery of aluminum (Al) adatoms on pristine graphene consequent to surface reactions of trimethylaluminum, (CH 3 ) 3 Al, precursor with graphene. 16 The achieved understanding of the complex precursor/surface dynamics and reaction mechanisms at atomistic level enables more efficient exploitation of the chemical precursors and better control of the MOCVD processes for the formation of 2D materials. 16 It is noticeable that currently available experimental data on intercalation phenomena under MOCVD conditions, which apply common metal organic precursors such as (CH 3 ) 3 Al and (CH 3 ) 3 Ga, is limited to the only two demonstrations of 2D AlN 11 and 2D GaN.…”

“…16 The achieved understanding of the complex precursor/surface dynamics and reaction mechanisms at atomistic level enables more efficient exploitation of the chemical precursors and better control of the MOCVD processes for the formation of 2D materials. 16 It is noticeable that currently available experimental data on intercalation phenomena under MOCVD conditions, which apply common metal organic precursors such as (CH 3 ) 3 Al and (CH 3 ) 3 Ga, is limited to the only two demonstrations of 2D AlN 11 and 2D GaN. 12 The present study corroborates MOCVD of AlN on epitaxial graphene with surface and interface characterization and establishes a link to our previous comprehensive AIMD simulations of the (CH 3 ) 3 Al/graphene surface reactions.…”

Molecular dynamics simulation of graphene sinking during chemical vapor deposition growth on semi-molten Cu substrate

“…Before graphene islands form, various intermediates such as carbon dimers, atomic carbon nanoarches or networks of carbon clusters, have been observed both in early experiments 18,19 and theoretic calculations [20][21][22] . For instance, based on densityfunctional molecular dynamics simulations, the very intricate pathways of reaction for metal organic chemical vapor deposition (MOCVD) of AlN on graphene can be identified at the atomic level with rich chemistry uncovered 23 . Unexpected defects such as pentagons usually appear during the nucleation stage and degrade the final quality of CVD-grown graphene.…”

Molecular Dynamics Investigation of Graphene Nanoplate Diffusion Behavior in Poly-α-Olefin Lubricating Oil

“…However, limited efforts have been devoted to the investigations on the dispersion behavior of graphene from the microscopic perspective. In order to understand the microscopic behavior and obtain details that are inaccessible from experiments, molecular dynamics (MD) simulations were selected by many researchers [28][29][30][31][32][33][34]. Saathoff et al [35] explored how three different edge terminations affected the dispersion stability of graphene in n-methyl-pyrrolidone (NMP) via MD simulations.…”