Growth Kinetics of Two-Dimensional Hexagonal Boron Nitride Layers on Pd(111).

Arias, Pedro; Ebnonnasir, Abbas; Ciobanu, Cristian V; Kodambaka, Suneel · Nano Lett · 2020

basic_science · Level V

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Abstract

Using <i>in situ</i> 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<sup>-6</sup> 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.