Comprehensive characterization of high-quality hexagonal boron nitride ultra-thin films grown by scalable ion beam assisted deposition

Hexagonal boron nitride (h-BN) is a key material for 2D heterostructures and electronic devices. It has been widely employed as encapsulant, dielectric barrier and, mainly, as a substrate for graphene since it significantly enhances its electronic properties and in particular the mobility of the charge carriers. However, these advances are to a great extent restricted to laboratory-scale experiments due to the limited scalability of current h-BN growth methods. In this work, we present an in-depth study of h-BN thin films grown by ion beam assisted deposition (IBAD), a versatile and scalable technique that enables the synthesis of high-quality ultra-flat layers with tunable thickness on metallic, semiconducting, or insulating substrates. Comprehensive structural, optical, and morphological characterization of the h-BN films was performed using complementary spectroscopic and advanced microscopy techniques. Our results reveal the growth of highly in-plane textured nanocrystalline h-BN layers exhibiting very low defect density and ultraflat surfaces with a wide bandgap around 5.35 eV. These findings make IBAD a promising method for the scalable growth of highly performing h-BN thin films for integration as substrates in graphene-based devices.