Title: Depth resolved chemical speciation of a superlattice structure,
Abstract: We report results of simultaneous x-ray reflectivity and grazing incidence
x-ray fluorescence measurements in combination with x-ray standing wave
assisted depth resolved near edge x-ray absorption measurements to reveal new
insights on chemical speciation of W in a W-B4C superlattice structure.
Interestingly, our results show existence of various unusual electronic states
for the W atoms especially those sitting at the surface and interface boundary
of a thin film medium as compared to that of the bulk. These observations are
found to be consistent with the results obtained using first principles
calculations. Unlike the conventional x-ray absorption measurements the present
approach has an advantage that it permits the determination of depth resolved
chemical nature of an element in the thin layered materials at atomic length
scale resolutions.