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Single-crystal Au(111), renowned for its chemically inert surface, long-range "herringbone" reconstruction, and high electrical conductivity, has long served as an exemplary template in diverse fields, e.g. , crystal epitaxy, electronics, and electrocatalysis. However, commercial Au(111) products are high-priced and limited to centimeter sizes, largely restricting their broad applications. Herein, a low-cost, high-reproducible method is developed to produce 4 in. Au(111) single crystals from commercial Au foils, via an abnormal grain growth process. This methodology involves the initial preparation of a (100)-textured Au polycrystalline foil, followed by the evolution and continuous expansion of an Au(111) abnormal grain through one-site stress loading and stress-relief annealing in an Ar/H 2 atmosphere. Theoretical simulations indicate that stress/strain and high-temperature treatments in the H 2 atmosphere induce an intermediate disordered state, facilitating the evolution from polycrystalline Au(100) foil to single-crystal Au(111) foil. Furthermore, the resulting Au(111) foils have been utilized as model substrates for the oriented growth of two-dimensional transition metal dichalcogenides and their heterostructures with graphene. This work hereby puts forward an effective approach for large-scale, cost-effective production of metal single crystals, potentially revolutionizing their applications across various fields, from materials sciences to electronics and catalysis. more...

The epitaxial growth of wafer-scale two-dimensional (2D) semiconducting transition metal dichalcogenides (STMDCs) single crystals is the key premise for their applications in next-generation electronics. Despite significant advancements, some fundamental factors affecting the epitaxy growth have not been fully uncovered, e.g., interface coupling strength, adlayer-substrate lattice matching, substrate step-edge-guiding effects, etc. Herein, we develop a model system to tackle these issues concurrently, and realize the epitaxial growth of wafer-scale monolayer tungsten disulfide (WS 2 ) single crystals on the Au(111) substrate. This epitaxial system is featured with good adlayer-substrate lattice matching, obvious step-edge-guiding effect for the unidirectionally aligned nucleation/growth, and relatively weaker interfacial interaction than that of monolayer MoS 2 /Au(111), as evidenced by the evolution of a uniform Moiré pattern and an intrinsic band gap, according to on-site scanning tunneling microscopy/spectroscopy (STM/STS) characterizations and density functional theory calculations. Intriguingly, the unidirectionally aligned monolayer WS 2 domains along the Au(111) steps can behave as ultrasensitive templates for surface-enhanced Raman scattering detection of organic molecules, due to the obvious charge transfer occurred at substrate step edges. This work should hereby deepen our understanding of the epitaxy mechanism of 2D STMDCs on single-crystal substrates, and propel their wafer-scale production and applications in various cutting-edge fields. more...

Epitaxial growth of wafer-scale monolayer semiconducting transition metal dichalcogenide single crystals is essential for advancing their applications in next-generation transistors and highly integrated circuits. Several efforts have been made for the growth of monolayer MoS 2 single crystals on high-symmetry Au(111) and sapphire substrates, while more prototype growth systems still need to be discovered for clarifying the internal mechanisms. Herein, we report the epitaxial growth of unidirectionally aligned monolayer MoS 2 domains and single-crystal films on low-symmetry Au(101) vicinal facets via a facile chemical vapor deposition method. On-site scanning tunneling microscopy observations reveal the formation of a specific rectangular Moiré pattern along the [101̅] step edge of Au(101) and along its perpendicular direction. The perfect lattice constant matching of MoS 2 /Au(101) along the substrate high-symmetry directions ( i.e. , Au[101̅], Au [010]) as well as the step-edge-guiding effect are proposed to facilitate the robust epitaxy. Multiscale characterizations further confirm the domain-boundary-free feature of the monolayer MoS 2 films merged by unidirectionally aligned monolayer domains. This work hereby puts forward a symmetry mismatched epitaxial system for the direct synthesis of monolayer MoS 2 single crystals, which should deepen our understanding about the epitaxy of 2D layered materials and propel their applications in various fields. more...