Growth of Open Honeycomb-like Sn Structures on Ag(111) at Low Temperatures

We studied, with a combination of low-energy electron diffraction (LEED) and scanning tunneling microscopy (STM) experiments and density functional theory (DFT) calculations, the growth of Sn deposited on the Ag(111) surface kept at low temperatures (<170 K). The LEED experiments show the formation of two phases, a (4 x 4) phase for coverage between 0.17 ML and 0.65 ML and a (root 7 x root 7)R19 degrees phase that appears at a coverage of similar to 0.75 ML. High-resolution STM images for a coverage of 0.37 ML, corresponding to the first phase, show nearly planar islands presenting a local order with a 4 x 4) periodicity. The formed Sn overlayer presents close (triangles) and open honeycomb-like (pentagons and deformed hexagons) structures. DFT calculations show that Sn adatoms should have a high mobility even at low temperatures and that a characteristic of the Sn layer is the coexistence of Sn atoms with three and four neighbors.