Coherently confined single-metal-atom chains in 2D semiconductors
Résumé
Single-metal-atom chains (SMACs) possess a variety of unique properties and functionalities but suffer from ambient vulnerability due to their delicate oneatom-width structures. While some SMACs can be effectively stabilized by nanochannel confining, it remains a pressing challenge to experimentally realize more versatile atomic chains with sufficient stability and extended length. Here, we propose a computational protocol to identify transition metals capable of forming SMACs along mirror twin boundaries in twodimensional metal dichalcogenides. Taking MoS 2 as a prototypical example, our thermodynamics and kinetics calculations indicate that Co, Ni, Rh, Pd, and Pt atoms can be enticed by the progressive formation of mirror twin boundaries to yield robust SMACs; whereas other transition metal elements tend to result in either substitutional doping or nanoclusters. These findings are supported by successful experimental synthesis of Co-, Ni-, Pd-and Pt-based SMACs using a chemical vapor co-deposition method, which exhibit high stability due to their covalent bonding with MoS 2 grains. These results lay a solid foundation for investigating exotic transport behaviors within extremely confined channels.
Dimensionality is a key factor determining the properties and functionalities of nanomaterials, since it dictates how electrons interact and behave by altering the symmetry and potential fields in materials. For instance, zero-dimensional (0D) nanoclusters exhibit quantized energy levels, while two-dimensional (2D) materials provide delocalized states of electrons confined in a planar space. Among them, onedimensional (1D) nanostructures have attracted special research interest 1,2 , since they represent the smallest dimension that maintains efficient electron transports, and, thus, have been deemed critical to the functionality and integration of nanoscale devices 3 . Single-metalatom chains (SMACs)-the ultimate manifestations of 1D structures-can confine electrons within an absolutely 1D space. This characteristic renders SMACs as a unique platform to investigate a series of intriguing quantum transport behaviors and correlation effects 4,5 , including quantized conductance 6,7 , magnetoresistance 8 , Peierls transition 9 and Tomonaga-Luttinger liquid 10-12 , opening up a wealth of opportunities for cutting-edge applications in electronics 13 , magnetism 14 , and optics 15 .
There have been two typical synthesis approaches for fabricating SMACs, one is the top-down mechanical stretching method for suspended SMACs, and the other is the self-assembly method for supported SMACs. However, the atomic chains fabricated using these
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