Standing-Wave X-ray Photoemission Spectroscopy (SW-XPS): A Methodological Overview for Non-Destructive Depth Characterization of Buried Interfaces †

Giuseppina Conti; Henrique Perin Martins; Slavomir Nemšák

doi:10.53941/ps.2026.100020

Abstract

Buried interfaces govern the functional properties of a wide range of technologically important material systems, from complex oxide heterostructures and spintronic multilayers to photoresist films and electrochemical interfaces. Yet their non-destructive, chemically specific, and depth-resolved characterization remains one of the central analytical challenges in modern materials science. This paper reviews the methodology of standing-wave X-ray photoelectron spectroscopy (SW-XPS), a synchrotron-based technique that combines the chemical and electronic state sensitivity of XPS with intrinsic depth selectivity, providing non-destructive access to buried interfaces with nanometer to sub-nanometer depth resolution across a multilayer stack. Two principal geometries are reviewed: Bragg-reflection SW-XPS, suited to periodic multilayer systems, and near-total-reflection SW-XPS (NTR-XPS), applicable to any smooth reflective substrate. Although originally developed for solid/solid interface characterization, SW-XPS has recently been extended to solid/gas and solid/liquid interfaces. Through two illustrative case studies drawn from the authors’ previously published work, Bragg-reflection SW-XPS applied to a multiferroic heterostructure, and NTR-XPS applied to EUV lithography photoresist films, the analytical capabilities of each geometry are demonstrated. This overview is aimed at spectroscopists new to the technique and at researchers seeking a non-destructive, depth-resolved alternative to established interface characterization methods.

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