In this sample, we also observe the presence of a turbostratic BN (t-BN) phase above the terminated epitaxial h-BN, that prevails with increasing film thickness. It is also possible to identify local r-BN stacking, marked using dashed circles in the HRTEM, which failed to establish a continuous epitaxial growth. An EELS elemental depth profile of the film was acquired to explore the film chemistry given the sudden termination of the epitaxial growth. As can be observed, the film exhibits a negligible carbon content directly after the onset of h-BN growth but increases at around ~4 nm after h-BN nucleation and continues increasing with film thickness until it saturates in the t-BN. Films deposited using TMB show this t-BN formation on both substrates, while films grown using TEB in contrast to the film in Fig. . The EELS depth profiles in the latter case show a steep increase in carbon content after terminating the h-BN growth (Fig. ). The EELS depth profiles for the other samples aligned with their respective HRTEM micrographs, for the less ordered growth regions, are available in the supporting information (Figs. ).