Recently we have succeeded in fabricating a zero-gradient nano-stepped surface (ZGNS) on Au(111). A distinct feature of this type of zero-gradient nano-stepped surface is that in the direction perpendicular to the steps, an up step is always followed by a down step. Thus, there are equal numbers of up and down steps, making such a surface nominally flat, and hence the name "zero gradient". A zero-gradient stepped surface cannot be made using the same method used to create a vicinal surface. So far the only zero-gradient stepped surface is created on the (111) surface of gold where atoms are extracted from a naturally existing step by the STM tip and allowed to reassemble into rather regularly spaced narrow fingers. The zero-gradient stepped surface differs from vicinal surfaces, not just in structural appearance, but more importantly in the energetics. For a vicinal surface, the atomic structure of all steps is intrinsically the same, and the step-step interaction arises between the same type of steps. For a zero-gradient stepped-surface, adjacent steps are of different signs (+ for an up step and – for a down step). Since the ZGNS consists of an array of aligned nano-fingers, a thorough understanding of the atomic structure and stability of individual fingers becomes critically important in elucidating the physical properties of a ZGNS as a whole. Here we report our recent findings from STM manipulations of nanofingers at both room temperature and 35 K. We find that there exists a minimum width, 3.5 nm or 14 atoms, associated with a stable finger as well as a close link between the finger stability and the normal herringbone reconstruction on the Au(111) surface. The ZGNS provides a unique platform for the study of step-step interactions between two types of step edges separated with nanometer distances.
References:
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