  We investigate quasi one-dimensional atomic chains on Si(553)-Au with a
scanning tunneling microscope (STM). The observed periodicity at the Si step
edge can be altered by the STM and depends on the magnitude of the tunneling
current. In a recent report this reversible structural transition was
attributed to transient doping with a characteristic time scale of a few
milliseconds. Here we explore the evolution of the STM topography as a function
of the magnitude of the tunneling current for a wide temperature range. Based
on a decomposition of topographic line profiles and a detailed Fourier analysis
we conclude that all observed currentdependent STM topographies can be
explained by a time-averaged linear combination of two fluctuating step-edge
structures. These data also reveal the precise relative alignment of the
characteristic STM features for both phases along the step edges. A simple
diagram is developed, presenting the relative contribution of these phases to
the STM topography as a function of tunneling current and temperature. Time-
and current-dependent measurements of fluctuations in the tunneling current
reveal two different transition regimes that are related to two specific
current injection locations within the surface unit cell. A method based on
spatially resolved I(z)curves is presented that enables a quantitative analysis
of contributing phases.
