We have investigated methods for cleaning de-etched polycrystalline tungsten tips for scanning tunnelling microscopy (STM). The cleaning methods include Ar-ion sputtering, heating, chemical treatments and Ne-ion self-sputtering. We correlate transmission electron microscopy images of the tip, field-emission data from the tip and images of a clean Cu(111) surface to find an optimum procedure for STM imaging. Clean and sharp tips are made by sputtering, combined with careful heating by electron bombardment. We found that optimum sputtering was obtained either by use of a 4 keV Ar-ion gun for a few seconds or by self-sputtering with Ne ions for a few seconds or until decapitation occurs.

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