Self-assembly and Electronic Properties of Graphyne and Graphdiyne Molecular Wires on Metallic Surfaces
Molecular self-assembly on solid surfaces has been the subject of extensive research, motivated by both fundamental and technological interests. On the fundamental side, these studies seek to elucidate the mechanisms governing molecular self-assembly and the resulting surface structures. From an applied perspective, they provide a route toward controlling surface reactions and engineering molecular electronic devices. Here, based on first-principles density functional theory calculations, we present a comprehensive study of self-assembled molecular wires (MWs), composed of graphyne (GY(1D)) and graphdiyne (GYD(1D))-like structures, adsorbed on Au(111), Ag(111), and Al(111) surfaces. Our total-energy calculations reveal that non-aligned MW arrays are energetically preferred on all three metal substrates. The GY(1D) and GYD(1D) molecular wires interact with the metal surfaces through van der Waals (vdW) forces, while their molecular orbitals do not contribute to the formation of metallic interface states. Simulated X-ray photoelectron spectroscopy (XPS) spectra reveal that the C 1s spectral features of the molecular wires are largely preserved upon adsorption, while the absolute binding energies undergo a substantial downshift that is nearly independent of the metal substrate, indicating that metallic screening effects dominate the adsorption-induced core-level shifts. Electronic band-structure calculations further show that the semiconducting character of the molecular wires is retained, resulting in vdW metal-semiconductor heterostructures in which the semiconducting component consists of one-dimensional semiconducting channels. These findings demonstrate that self-assembled graphyne- and graphdiyne-based molecular wires on metal surfaces provide a promising platform for the realization of low-dimensional molecular electronic devices.