Chemical-specific imaging of multicomponent metal surfaces on the nanometer scale by scanning tunneling spectroscopy

The topographic and chemical surface structure of a submonolayer iron film on a W(110) substrate has been studied by combined scanning tunneling microscopy and spectroscopy. Local tunneling spectra revealed a pronounced difference in the electronic structure between nanometer-scale iron islands of monolayer height and the bare W(110) substrate. In particular, a pronounced empty-state peak at 0.2 eV above the Fermi level has been identified for the iron islands. Based on the pronounced difference in the local tunneling spectra measured above the iron islands and the tungsten substrate, chemical-specific imaging was achieved by performing spatially resolved measurements of the differential tunneling conductivity dI/dU (x, y) at selected sample bias voltages.