Ordering of iron phthalocyanines on Ni(111) via a graphene buffer layer

Molecular spintronics exploits the spin-dependent properties emerging at hybrid interfaces between magnetic substrates and molecular layers, offering promising routes toward novel spin-based devices. In this work, we present a comparative investigation of the structural, morphological, and electronic properties of iron(II) phthalocyanine (FePc) monolayers grown on bare Ni(111) and on graphene-covered Ni(111) substrates. High-quality graphene was prepared by chemical vapor deposition, and FePc films were deposited under ultra-high-vacuum conditions. The systems were characterized by Auger electron spectroscopy (AES), low-energy electron diffraction (LEED), and scanning tunneling microscopy/spectroscopy (STM/STS). AES analysis reveals subtle but significant differences in the carbon KVV line shape, indicating a higher degree of molecular order when FePc is deposited on graphene/Ni(111). STM measurements corroborate this finding, showing that graphene promotes the formation of compact, homogeneous molecular layers with locally ordered domains, whereas FePc deposited directly on Ni(111) exhibits a strongly disordered morphology, likely related to a different adsorption geometry and stronger molecule–substrate interactions. STS measurements demonstrate that, despite the distinct growth modes, the main molecular electronic features are preserved in both systems. Overall, our results highlight the key role of graphene as an effective buffer layer, capable of modulating molecule–substrate interactions, thereby providing a versatile platform for future studies of electronic and magnetic coupling in molecular spintronic systems.