Atomic-Scale Observations of the Immiscible Melted Metals Confined in a Single-Atom Layer

Elucidating how changing of the dimensionality affects the property of the matter is the key challenge problem of the nanoscience. In particular, it has recently been reported that 2D liquids have fundamentally different dynamic properties to 3D liquids. Herein, the ultimate physical limit is addressed, when the liquid is confined to a single-atom layer. The case has been realized with the Tl-Pb alloy layer grown on Si(111) substrate terminated by a single-layer NiSi2$\left(\text{NiSi}\right)_{2}$. At room temperature, the alloy behaves as a system of the immiscible melted metals confined in a single-atom layer. In the scanning tunneling microscopy observation, Tl and Pb arrays have different contrasts that allows a direct visualization of evolution of the forming structures within atomic layer, as a function of the time and layer composition. In particular, it has been found that the structures look much like the Turing patterns. The obtained experimental dataset, especially the recorded STM videos, is believed to provide a hint for the prospective theoretical understanding of the dynamics of the single-atom-thick liquids.