  Local structural and electronic properties of thin Pb(111) films grown on
Si(111)7x7 surface are experimentally studied by means of low-temperature
scanning tunneling microscopy and spectroscopy (STM/STS). It is shown that the
visible height $h$ of the monatomic step on Pb(111) surface demonstrates
oscillatory dependence on bias voltage $U$. The period of these oscillations
coincides with the period of the oscillations of both local tunneling
conductance ($dI/dU$) and the rate of the STM tip displacement ($dZ/dU$) at
sweeping $U$. It points to the fact that the observed oscillations of the
visible height of monatomic Pb(111) step are controlled by coherent resonant
tunneling of electrons from the STM tip to Pb(111) film through quantum-well
states in thin Pb(111) film. We argue that the maximum and minimum visible
heights of the monatomic Pb(111) step correspond to the bias voltages, at which
local densities of states for the Pb(111) terraces of different thicknesses are
equal.
