ReaxFF Force Field Development for Gas-Phase hBN Nanostructure Synthesis

Two-dimensional
(2D) hexagonal boron nitride materials are isomorphs
of carbon nanomaterials and hold promise for electronics applications
owing to their unique properties. Despite the recent advances in synthesis,
the current production capacity for boron nitride (BN) nanostructures
is far behind that for carbon-based nanostructures. Understanding
the growth mechanism of BN nanostructures through modeling and experiments
is key to improving this situation. In the current work, we present
the development of a ReaxFF-based force field capable of modeling
the gas-phase chemistry important for the chemical vapor deposition
(CVD) synthesis process. This force field is parameterized to model
the boron nitride nanostructure (BNNS) formation in the gas phase
using BN and HBNH as precursors. Our ReaxFF simulations show that
BN is the best of these two precursors in terms of quality and the
size of BNNSs. The BN precursors lead to the formation of closed BNNSs.
However, BNNSs are replaced with complex polymeric structures at temperatures
of 2500 K and higher due to entropic effects. Compared to the BN precursors,
the HBNH precursors form relatively small, flat, and low-quality BNNSs,
but this structure is less affected by temperature. Additives like
H2 significantly affect the BNNS formation by preventing
closed BNNS formation. Our results show the ReaxFF capability in predicting
the BN gas-phase chemistry and BNNS formation, thus providing key
insights for experimental synthesis.