Two-dimensional (2D) layered materials, owing to a wide range of properties (e.g., graphene is metallic, hBN is insulating, and MoS₂ is semiconducting), have attracted considerable attention over the past decade. hBN is isostructural to graphene and is considered an ideal dielectric for the fabrication of vertical 2D layered heterostructures with potential applications in optoelectronics and nanoelectronics. hBN layers are commonly grown on metal substrates. In contrast to free-standing hBN layers, substrate-supported hBN can be metallic, semiconducting, or insulating, depending on the chemistry and electronic structure of the hBN/substrate interface. Moreover, due to relatively weak van der Waals interactions between the 2D layer and the substrate, orientational registry of the layers with the substrate is not expected and is often difficult to control. While the growth and electronic structure of graphene layers have been fairly well studied, relatively little is known concerning the mechanisms underlying the growth of the hBN layers and the influence of hBN domain orientation (with respect to the substrate) on its electronic properties.

Using in situ ultra-high vacuum scanning tunneling microscopy (UHV STM), we investigated the chemical vapor deposition (CVD) kinetics of hBN on Pd(111). STM images are acquired during CVD of borazine as a function of substrate temperature, borazine flux, and deposition time. We observe the nucleation and growth of chemisorbed borazine islands on the Pd surfaces. Furthermore, we investigated the surface structure of hBN domains on Pd(111) using STM, scanning tunneling spectroscopy (STS), and density functional theory (DFT) calculations. STM images acquired from the hBN/Pd(111) sample reveal moiré patterns with at least four different periodicities λ corresponding to four rotational domains of hBN. From the STM images, we measured the surface corrugations in each of the moiré patterns and found that the corrugation amplitude Δz depends on the tunneling bias and increases with increasing λ. We suggest that Δz is a measure of hBN-Pd(111) interaction strength and attribute the higher corrugation amplitudes to stronger interactions between the hBN domains and the Pd(111). We expect that similar approach could be used to investigate growth kinetics and orientation-dependent interactions in other substrate-supported 2D layers with large lattice mismatch with respect to the substrate.