Rutherford backscattering spectrometry: A multimodal ion beam analysis technique for evaluating elemental depth profiles and radiation hardness for space photovoltaics applications

Given the well-established possibility of elemental migration in perovskite devices, often driven by multiple stressors and contributing to device degradation, it is essential to evaluate and quantify their elemental distribution using characterization techniques that minimize measurement-induced inter-mixing of elements. Techniques like time-of-flight secondary ion mass spectrometry and x-ray photoelectron spectroscopy based depth profiling are commonly employed for such analysis. However, despite their feasibility and effectiveness, these methods can inadvertently cause additional damage to the delicate perovskite as well as other organic structures present in the devices, which are vulnerable to preferential elemental sputtering and compositional matrix mixing effects. Such issues can lead to quantification errors and unwanted artifacts, particularly when using keV-range heavy ions such as Ar+, O+, Cs+, or Ar cluster ions for sputtering. In contrast, Rutherford Backscattering Spectrometry (RBS) utilizing MeV range energetic He or H ions is generally regarded as a non-destructive technique that does not require reference standards or extensive sample preparation. It provides a comprehensive analysis of the composition, thickness, and depth profiles of the elements present in the device layers, while also enabling a concurrent evaluation of radiation tolerance with the probing light ion beam (e.g., H+ and He+). This perspective highlights the key benefits of using RBS for elemental depth profiling and migration in perovskite-based devices and explores recent developments, ongoing challenges, and efforts toward achieving accurate quantitative analysis in complex multilayer thin-film structures.