Observation of ordered structures for S/Cu(111) at low temperature and coverage

Abstract

Via scanning tunneling microscopy and low energy electron loss diffraction we observe ordered low-temperature surface structures for S/Cu(111) at low-S coverage and characterize the system also with core level photoemission. The first structure to appear upon S deposition is honeycomblike with a large mesh $[(\sqrt{43}\ifmmode\times\else\texttimes\fi{}\sqrt{43})R\ifmmode\pm\else\textpm\fi{}7.5\ifmmode^\circ\else\textdegree\fi{}],$ a large nearest S-S distance $(\ensuremath{\sim}4\AA{})$ and low-ordering temperature $(<170\mathrm{K}).$ Islands of this structure are observed at low coverage $(\ensuremath{\theta}\ensuremath{\sim}0.05)$ and at $\ensuremath{\theta}\ensuremath{\sim}0.25$ nearly all of the surface area is covered.