Ultraflat honeycomb stanene nanoribbons on Au(111)

Abstract

Sn on Au(111) undergoes a structural and chemical evolution depending on the submonolayer coverage. After deposition of ≈ 2∕3 ML Sn, the coverage was controlled by temperature-driven desorption. Annealing to 450K produced the striped phase, which consists of alternating honeycomb and square-like Sn stripes, with periodicities ranging from Rec(13 × 2√3) to Rec(19 × 2√3),most commonly Rec(16 × 2√3). Honeycomb regions are atomically flat, with a Sn–Sn bond length of ≈2.88 Å. Low-energy electron diffraction (LEED), atomically resolved scanning tunneling microscopy (STM), and X-ray photoelectron spectroscopy (XPS) reveal structural and chemical transitions as a function of Sn coverage. Without further annealing, deposition yields a square-like X-phase atop an Au2Sn interface alloy. Annealing induces dealloying and the formation of the striped phase, while further desorption produces a √7 stretched honeycomb phase. Annealing above 480K, and at ≈ 0.35 ML coverage, the Au2Sn alloy reforms. For the striped phase, a model is proposed where square-like stripes grow on Au2Sn regions and honeycomb stripes on Au(111). The alternating regions correspond to zigzag stanene nanoribbons of ≈ 1.5nmto 3.2 nm width. The structural transitions of the Sn/Au(111) system highlight its structural versatility, driven by alloying–dealloying processes at the interface.