Direct observation of atomic planes in epitaxial multilayers by anodization spectroscopy

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Abstract
Using the technique of anodization spectroscopy we have shown that it is possible to directly observe individual atomic planes in high quality Nb/Ta epitaxial multilayers. The signal corresponding to the atomic planes is superimposed on the superlattice structure associated with the different anodization rates of the two metals. The results imply that an upper limit of less than 0.1 nm can be placed on the fundamental resolution of this novel measurement technique. As a test of this measurement we have obtained data from films grown on different orientation substrates, and have shown that the separation of the peaks corresponds to the known lattice spacings in the growth direction. The mechanisms responsible for the very uniform propagation of the anodization front and the consequent ability to observe directly the atomic planes normal to the exposed surface are discussed.