XPS depth profiling of functional materials: applications of ion beam etching techniques

Chemical analysis of functional materials has become one of the most intensively developing fields in current materials science due to the close association between the chemical composition and the physicochemical properties (or application) of materials. X-ray photoelectron spectroscopy (XPS) as a mature surface analytical technique plays an important and unique role in the materials community. XPS depth profiling combined with ion beam etching methods is a primary tool to study the chemical composition of functional materials at different scales from the surface to the bulk. This review aims to bring a landscape of typical applications of ion etching techniques in XPS depth profiling to the audience of general materials. According to the sputtering source, the ion etching techniques can be categorized into monatomic ion beam (MAIB), gas cluster ion beam (GCIB) and MAIB + GCIB modes, whose advances made in the past three decades are summarized in this work. The experimental examples of three etching modes are introduced to generalize their characteristics and application fields. Finally, the challenges and the prospects of the ion etching techniques in XPS analysis of materials are discussed.