# Depth resolved chemical speciation of a superlattice structure

## TL;DR

This study combines advanced x-ray techniques to achieve depth-resolved chemical speciation of tungsten in a superlattice, revealing unusual electronic states at surfaces and interfaces with atomic-scale precision.

## Contribution

It introduces a novel combination of x-ray methods enabling atomic-scale depth-resolved chemical analysis in layered materials, validated by first principles calculations.

## Key findings

- Discovery of unusual electronic states at surface and interface boundaries of W in the superlattice
- Demonstration of depth-resolved chemical state determination at atomic scale
- Correlation of experimental results with first principles calculations

## 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.