Low-temperature structure of S/Cu(111) - art. no. 155406

We use scanning tunneling microscopy (STM) and core and valence photoemissi on as well as low-energy electron diffraction to characterize recently disc overed S/Cu(111) surface structures that appear at low coverage below order ing temperatures of around 230 K. At even lower coverage ordered local arra ngements are observed near steps and dislocations. Of the laterally extendi ng structures one is open. and honeycomb (hc) like, while three other struc tures (I,II,III) are more complicated. It is suggested that the structures can be explained as reordered (0001) planes of CuS. Surprisingly the open h c structure gives room for the Cu(111) surface state according to photoemis sion and scanning tunneling spectra. Core level spectra provide support for one of the models proposed for an earlier studied room-temperature structu re [Cu(111)-( root 7x root7)R+/-19.1 degrees -S].