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Controlled surface charging as a depth-profiling probe for mesoscopic layers

Abstract

Probing the structure of material layers just a few nanometres thick requires analytical techniques with high depth sensitivity. X-ray photoelectron spectroscopy1 (XPS) provides one such method, but obtaining vertically resolved structural information from the raw data is not straightforward. There are several XPS depth-profiling methods, including ion etching2, angle-resolved XPS (ref. 2) and Tougaard's approach3, but all suffer various limitations2,3,4,5. Here we report a simple, non-destructive XPS depth-profiling method that yields accurate depth information with nanometre resolution. We demonstrate the technique using self-assembled multilayers on gold surfaces; the former contain ‘marker’ monolayers that have been inserted at predetermined depths. A controllable potential gradient is established vertically through the sample by charging the surface of the dielectric overlayer with an electron flood gun. The local potential is probed by measuring XPS line shifts, which correlate directly with the vertical position of atoms. We term the method ‘controlled surface charging’, and expect it to be generally applicable to a large variety of mesoscopic heterostructures.

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Figure 1: Schematic representation of the studied multilayer systems.
Figure 2: Spectral response to the electron flood-gun flux.
Figure 3: Plot of V0 versus overlayer thickness.
Figure 4: Depth profiling with accurately positioned markers.

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Acknowledgements

This work was supported by the Israel Science Foundation, and the Tashtiot Infrastructure Program of the Israel Ministry of Science.

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Correspondence to Israel Rubinstein.

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Doron-Mor, I., Hatzor, A., Vaskevich, A. et al. Controlled surface charging as a depth-profiling probe for mesoscopic layers. Nature 406, 382–385 (2000). https://doi.org/10.1038/35019025

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