Current-dependent periodicities of Si(553)-Au

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 [S. Polei et al., Phys. Rev. Lett. 111, 156801 (2013)]. 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 current-dependent 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.