特集論文
島津評論 83〔1・2〕 25～38 (2026)
要旨
X-ray photoelectron spectroscopy (XPS) is a well-established technique for quantitative surface analysis in both industrial and academic laboratories. The technique is used to determine elemental composition, chemical states, and electronic structure. Most commonly, it has been applied to well-defined, vacuum-compatible solids but characterisation by XPS is now rapidly expanding to encompass increasingly complex and non-conventional material systems. In this work, we explore recent advances to acquisition methods and instrument hardware that extend the use of XPS beyond conventional samples, enabling robust characterisation of heterogeneous and hydrated samples. This is demonstrated using examples including thin films for micro-electronics, functional biologically active thin films and cryogenically preserved soft matter.
The characterisation of hafnia/alumina nanolaminate bilayers with application in semiconductor devices is undertaken using higher energy X-ray excitation and angle-resolved XPS. This is a powerful analytical approach as it allows thin-film chemical characterisation, whilst mitigating sputter-induced effects that could be caused by more conventional ion sputter depth profiling.
Copper-based biocidal coatings are used to reduce the persistence of pathogenic bacteria and viruses on surfaces and act as sources of infection on contact. Here we show how XPS allows detailed insight into both lateral and depth-dependent composition through millimetre-scale mapping and sputter depth profiling. These approaches reveal non-uniform elemental distributions and subsurface diffusion of copper through titania overlayers. High-resolution spectra provide evidence of specific oxidation states critical to antimicrobial performance.
Innovations in sample preparation, most notably cryogenic workflows, are addressing long-standing challenges associated with analysing volatile or liquid-phase systems under ultra-high vacuum. Cryo-XPS, for example, enables the preservation of near-native states in functionalised nanoparticles, reducing artefacts induced by solvent removal and allowing more representative insights into real-world behaviour.
1Kratos Analytical Ltd, Manchester, UK
2X-Ray/Surface Business Unit, Analytical & Measuring Instruments Division, Shimadzu Corporation, Kyoto, Japan
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