Displacement thresholds and knock-on cross sections for hydrogenated h-BN monolayers

In the present article, the authors initially studied the effects of hydrogenation on the displacement threshold energies (E_d) of B and N atoms in h-BN nanosheets with the help of reaction force field (ReaxFF) based molecular dynamics simulations. Subsequently, the E_d values estimated for B, N and H atoms were used for predicting the knock-on cross section for these atoms against electron irradiation. The results show that in most of the cases the displacement threshold value deteriorates with hydrogenation. The redistribution of charge among different atoms with the increase in B-N bond length plays a significant role in deciding the displacement thresholds for B and N atoms. It was predicted with the help of obtained E_d values that in a lower energy range the H atoms have a higher knock-on cross-section than B and N atoms against electron irradiation. The results from this study lead the authors to recommend cautious use of transmission electron microscopy for the characterization of hydrogenated h-BN nanosheets.