SCANNING-TUNNELING-MICROSCOPY MEASUREMENTS OF THE LOCAL WORK FUNCTIONAROUND STEPS ON THE AU CU(111) SURFACE/

With a scanning tunneling microscope we have taken local work function images of the Au/Cu(111) surface. The local work function measured fr om large Au-covered terraces is in good agreement with the result obta ined by non-local techniques, and the local work function around step edges is significantly lower than that on terraces. The experimental d etails of the local work function lowering around a step can be reprod uced nicely with a simple simulation if a dipole moment row with a pro per linear density is put at the center of the step and if the influen ce of the topographic change of the step due to formation of the dipol e moment is taken into account. It is demonstrated that STM has the ab ility to reveal the details of how local work function varies around s teps and other defects on metal surfaces.