Unconventional Band Structure via Combined Molecular Orbital and Lattice Symmetries in a Surface‐Confined Metallated Graphdiyne Sheet

Abstract

Graphyne (GY) and graphdiyne (GDY)‐based monolayers represent the next generation two‐dimensional (2D) carbon‐rich materials with tunable structures and properties surpassing those of graphene. However, the detection of band formation in atomically thin GY/GDY analogues has been challenging, as both long‐range order and atomic precision have to be fulfilled in the system. Here, we report direct evidence of band formation in on‐surface synthesized metallated Ag‐GDY sheets with mesoscopic (∼1 µm) regularity. Employing scanning tunneling and angle‐resolved photoemission spectroscopies, energy‐dependent transitions of real‐space electronic states above the Fermi level and formation of the valence band are respectively observed. Furthermore, density functional theory (DFT) calculations corroborate our observations and reveal that doubly degenerate frontier molecular orbitals on a honeycomb lattice give rise to flat, Dirac and Kagome bands close to the Fermi level. DFT modeling also indicates an intrinsic band gap for the pristine sheet material, which is retained for a bilayer with h‐BN, whereas adsorption‐induced in‐gap electronic states evolve at the synthesis platform with Ag‐GDY decorating the (111) facet of silver. These results illustrate the tremendous potential for engineering novel band structures via molecular orbital and lattice symmetries in atomically precise 2D carbon materials.This article is protected by copyright. All rights reserved

Transmetalation in Surface-Confined Single-Layer Organometallic Networks with Alkynyl–Metal–Alkynyl Linkages

“…Although various OMNs have been constructed with selected molecular building blocks via consuming surface adatoms provided by the substrate underneath, the success rate for their realization is often unforeseeable and strongly substrate-dependent, limiting the general applicability of such functional organometallic materials. In particular, it has recently been shown that extended graphdiyne-like, alkynyl–silver–alkynyl, and alkynyl–gold–alkynyl honeycomb OMNs can be prepared successfully by applying on-surface synthesis strategies. − Yet, the large spectrum of metal centers and possible organic linkers calls for the identification of efficient routes to bestow the desired variety and versatility to the structural and electronic properties of such films.…”

“…22 This article is licensed under CC-BY 4 Organometallic bonding, mostly involving carbon−metal linkages, due to its generally covalent nature 23 and the reversibility associated with the binding characteristics, 24 may provide a powerful strategy for engineering surface-confined organic networks with appreciable robustness as well as impressive mesoscale regularity. 25,26 2D organometallic networks (OMNs) feature functional 2D materials with a significant promise. The often higher flexibility relative to purely covalent linking and the reversibility during the formation process in the low-dimensional environment of a surface offer the possibility of self-healing of defects, potentially affording higher order and tailored packing motifs and symmetry.…”