Surface step motion on the (001) surface of strontium titanate single crystals during DC electric field-assisted flash treatment

A DC electric field-assisted flash treatment was performed on the (001) surface of a SrTiO 3 single crystal on which a step-terrace structure had been formed in advance (by solution etching).The DC electric field was applied along the direction that the surface height increases (up-step) or decreases (down-step) for a very short treatment duration of 1 min.The step-terrace morphology on the (001) surface was observed by atomic force microscopy, and the results were primarily discussed in terms of step stabilization or destabilization.Applying the DC electric field in the up-step direction appeared to stabilize the steps overall, although slight wandering was observed.Conversely, the steps were destabilized when the DC electric field was applied in the down-step direction, and the steps wandered significantly, with terraces protruding in the direction that the surface height decreases.The dependence of the step-terrace morphology on the direction of the DC electric field was consistent with previous studies that employed static electric fields (without a flash event).However, the step-terrace morphology may eventually become destabilized when the DC flash treatment time is extended, regardless of the applied field direction, considering the treatment duration of 10 min used in a previous study.This is inferred to be attributed to the amount of material diffusion relative to that of surface diffusion, which is increased by athermal effects during flash treatment.