THEORY OF THE LOCAL DENSITY OF SURFACE-STATES ON A METAL - COMPARISON WITH SCANNING TUNNELING SPECTROSCOPY OF A AU(111) SURFACE

A simple theory of the effect of monatomic steps on the local density of surface states and on the conductance of a scanning tunneling microscope (STM) has been developed. This theory is based upon reflection and transmission amplitudes for surface electron waves. It is assumed that a step acts as a repulsive barrier, which is entirely consistent with experimental observations on the (111) surface of a Au single crystal. Comparison to experiment has been made for a flat surface to establish that the model for the tip and barrier is adequate. The theory for the conductance with the STM tip near a single step and in the center of a pit is shown to agree well with experiment. Theoretical results are also presented for a periodic array of steps for which one-dimensional Kronig-Penney bands should be observable, especially at reduced temperature.