Epitaxial Growth and Structural Evolution of Arsenic Nanostructures on Au(111): From Armchair Nanochains to Three Distinct As–Au Two-Dimensional Inorganic Porous Networks

Arsenic nanostructures have attracted significant attention due to their theoretically predicted bandgap modulation, exceptional in-plane carrier mobility, and nontrivial topological states. However, surface growth mechanisms of arsenic nanostructures remain unclear, which restricts their practical applications. In this study, we demonstrate the epitaxial growth of arsenic nanostructures on Au(111) whose phases can be controlled by stepwise thermal annealing (300–600 K). Utilizing in situ scanning tunneling microscopy (STM) and density functional theory (DFT) calculations, we identified four distinct growth phases: armchair-type arsenic nanochains, and three ordered arsenene-Au two-dimensional (2D) inorganic porous network structures (α-, β-, and γ-phase) with arsenene subunits interconnected via Au adatoms. Notably, the γ-phase network exhibits a 2√7 × 2√7 R19.13° superlattice symmetry analogous to reported Au–P systems on Au(111). The DFT-optimized models reveal a progressive growth mechanism in which arsenic undergoes a three-stage evolution: formation of armchair arsenic chains through adsorption decomposition of As4 clusters, surface alloying at 350 K, and surface gold atom migration accompanied by enhanced As–Au binding energy during high-temperature annealing (∼500 K). In this work, we expand the two-dimensional group VA material system by synthesizing three new As–Au structures and establish a thermal-activated phase transition pathway for constructing substrate-stabilized nanostructures.