Influence of Substrate van der Waals Interactions on the Structural Stability of Violet Phosphorus

The van der Waals (vdW) interactions between exfoliable materials and their supporting substrates—and how these interfacial forces affect the materials’ stability and interaction with the environment—remain poorly understood. In this work, we experimentally and theoretically investigate the role of vdW forces at the interface between the recently rediscovered wide band gap p-type vdW semiconductor material, violet phosphorus (VP), and various substrates (SiO₂, Mica, Si, and Au). We quantify how the interfacial vdW coupling influences VP’s environmental stability and its interaction with the surroundings. By combining infrared nanoimaging with theoretical modeling, we identify three key factors that govern VP’s behavior: the interfacial vdW force, the substrate’s hydrophobicity, and its surface roughness. Our findings reveal that VP remains stable for extended periods when exfoliated on SiO₂, followed by mica and Au, and exhibits the least stability on Si substrates. These insights provide practical guidance for substrate selection in preparing vdW materials and underscore the critical role of interfacial forces in modulating their physical properties.