Theoretical aspects of scanning tunneling microscopy

Two of the most interesting fields to which the recently discovered Scanning Tunneling Microscopy (STM) has been applied, are surface topography and surface spectroscopy. In this paper theoretical work carried out to interpret STM images and spectroscopic data will be reviewed. Special emphasis is made on models introduced to study tunneling through localised states (image or surface states). The close relationship between surface spectroscopy and surface topography, as viewed by STM, is also highlighted. Besides, theoretical analyses of the mechanisms involved in energy dissipation in STM will be also discussed; both metallic and insulating samples will be considered.