Zinc and cadmium: XPS chemical state determination and auger peak curve-fitting procedures

Zinc and cadmium are essential elements in a wide array of industrial applications, yet accurately determining the chemical states of their compounds using X-ray photoelectron spectroscopy remains challenging due to similarities in photoelectron signals among different species. This study presents a comprehensive reference dataset for over 40 zinc and cadmium species, including both commercially available compounds and naturally occurring minerals. The dataset features detailed measurements of core-level photoelectron signals, X-ray-induced Auger electron signals, and relevant counter-ion signals. To enhance chemical state identification, the utility of the modified Auger parameter and Wagner plots is examined. For mixed oxide systems, curve-fitting procedures based on Auger signals are demonstrated, offering improved speciation accuracy compared to interpretations based solely on photoelectron data. Best practices for Auger signal modelling are discussed, with particular attention to stoichiometric constraints and interference from common surface contaminants such as sodium. This dataset is intended to support researchers in achieving more reliable interpretation of zinc and cadmium XPS data, thereby advancing surface chemical analysis in both fundamental and applied research