Nonalloying surface reconstructions of ultrathin Sn films on Cu(111) investigated with LEED, XPS, and photoelectron extended fine structure analysis

By preventing surface alloying during growth of Sn on Cu(111) at 100 K, we discovered two novel nonalloying surface reconstructions, denoted as lower-coverage (LC) and higher-coverage (HC) phases. They were investigated with low energy electron diffraction (LEED), x-ray photoemission spectroscopy (XPS), and analysis of photoelectron extended fine structure (PEFS). The LC phase has a p(2×2) structure with one Sn atom per unit cell, corresponding to a Sn coverage 0.25 ML; the HC phase has a structure of M=(2113) (matrix notation) with two Sn atoms per unit cell, corresponding to a Sn coverage 0.40 ML. Structural models for the two phases are proposed.