Strain-Driven Honeycomb Reconstruction of Multilayered Rh/Pt(111)

This study reports on a long-range ordered honeycomb surface structure formed by annealing of Rh multilayers on Pt(111). Scanning tunneling microscopy reveals a honeycomb network with a lateral periodicity of ∼15 nm and ∼0.07 nm corrugation, most pronounced at ∼11.2 ML Rh coverage and annealing at 700 K. In situ X-ray photoelectron spectroscopy at 700 K, combined with diffusion calculations, indicates Pt surface enrichment and Pt-Rh intermixing driven by surface and grain boundary diffusion, while bulk diffusion remains negligible. At 900 K, bulk diffusion becomes dominant, and the honeycomb structure is disrupted upon prolonged annealing. The honeycombs arise from an interplay among Rh coverage, annealing time and temperature, and Pt-Rh mixing dynamics and are driven by interfacial strain due to lattice mismatch, which relaxes through surface reorganization. These findings highlight the delicate interplay of atomic diffusion and strain-driven reconstruction in bimetallic nanostructure evolution.