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Description
Two-dimensional metal-organic frameworks offer a highly versatile platform for designing novel electronic materials. Their electronic band structures are typically constrained by rigid framework compositions dictated by the discrete identities of the constituent metal ions and organic ligands[1]. Achieving continuous electronic tunability requires the development of structurally invariant but compositionally variable coordination lattices[2]. Utilizing a tetracyanoquinodimethane (TCNQ)-based network grown on a Ag(100) surface, a mixed-metal bimetallic framework can be achieved through sequential metal incorporation. An initial, partially coordinated Ni-TCNQ structure is saturated with a second transition metal species, specifically Cobalt, forming a fully coordinated two-dimensional network resulting in a two-dimensional Ni-Co coordinating alloy.
Scanning tunnelling microscopy and low-energy electron diffraction verify that the low-valence Ni and Co transition metal centers occupy equivalent molecular coordination sites while preserving the long-range crystalline order of the parent lattice. Momentum-resolved photoemission spectroscopy demonstrate a significant influence of the bimetallic mixing on the dispersive electronic band structure of the hybridisation network. The macroscopic bandwidth and the band curvature evolve systematically as a direct function of the transition metal composition ratio. This compositional flexibility enables the quantitative control of the charge carrier effective mass and intrinsic dispersive properties without disrupting the inherent electronic delocalization of the two-dimensional molecular network.
[1] D. Baranowski et al. ACS Nano 18, 30 (2024)
[2] S. Mearini et al., Adv. Science 11, 38 (2024)