Growth Kinetics of Two-Dimensional Hexagonal Boron Nitride Layers on Pd(111)
Pedro Arias, Abbas Ebnonnasir, Cristian V. Ciobanu, Suneel Kodambaka
Abstract
Using in situ variable-temperature scanning tunneling microscopy (300–673 K) during chemical vapor deposition of two-dimensional hexagonal boron nitride (hBN) on Pd(111) from borazine precursor at pressures up to 10–6 mbar, we identify the mechanisms leading to carpetlike uphill or downhill growth across the Pd steps. Deposition at a higher rate and lower temperature promotes uphill growth via preferential attachment at the ascending and descending step-edges, whereas a lower deposition rate and higher temperature lead to downhill growth via nucleation and growth of islands on Pd terraces. We attribute this unusual growth behavior to differences in temperature-dependent rates of hBN deposition at the steps versus on the Pd terraces. Our results illustrate how growth mechanisms can be activated by a pair of parameters (substrate temperature and partial pressure of borazine) and provide new insights into the mechanisms underlying carpetlike growth of hBN and other layered materials.