We examined the modifications in the electronic and structural properties of hexagonal boron nitride (hBN) grown by the CVD process on curved transition metal substrates, namely c-Pt(111) and c-Ni(111) crystals, both before and after Europium (Eu) intercalation. Numerous emerging devices are proposed to rely on 2D materials such as Graphene, hexagonal boron nitride, and others. These materials are generally grown by CVD processes on metal substrates such as Copper, Nickel, or Platinum. The quality of growth significantly relies on both the crystallinity of the substrate and the interaction between the overlayer and the substrate. The characteristics of the interface can be altered by adjusting the crystal structure and step density of the substrate. This was demonstrated through the growth of hBN on curved crystals, where the substrate faceting varied between strong (Ni) [1], intermediate (Rh) [2] and weak (Pt) [3]. Experimentally, the structural properties were characterized using Low-energy electron diffraction (LEED) and scanning tunneling microscopy (STM). Stable facets were observed to form during hBN growth on the substrates. However, after Eu intercalation, changes in the stable facets were observed. The LEED detected the formation of Eu-TM alloy. Furthermore, the electronic properties were carried out using x-ray photoelectron spectroscopy (XPS) and angle-resolved photoemission spectroscopy (ARPES). Additionally, we investigated the ability of the hBN layer to protect Eu on both curved Pt(111) and Ni(111) substrates. Our results suggest that the protective effect of the hBN layer on Eu was incomplete and exhibited variation along the curved surfaces of the crystals. Specifically, on c-Pt(111), better Eu protection was noted at the (111) surface compared to the steps. Conversely, on c-Ni(111), the opposite trend was observed. This variation could potentially be attributed to the influence of the mismatch between the hBN and the substrates. The incomplete protection of Eu due to defects and growth boundaries in the hBN layer led to the oxidation of Eu. Theoretical calculations were conducted to gain further insights into the formation of stable surface facets by investigating the structural properties of hBN on various Pt vicinal surfaces.
 

References
1- Fern´andez, Laura, et al. 2D Materials (2019) 6, 025013.
2- Ali, Khadiza, et al. Adv. Sci. (2021) 8, 2101455.
3- Bakhit, Alaa Mohammed Idris, et al. Science Talks (2022) 4, 100071.
4- Bakhit, Alaa Mohammed Idris, et al. Nanoscale (2023), 15.27, 11517-11528.