The Impact of Gas Cluster Ion Beam Sputtering on the Chemical and Electronic Structure of Methyl Ammonium Lead Iodide Thin Films

The stability and performance of metal halide perovskite (MHP) optoelectronic devices are significantly influenced by the chemical and electronic properties of their interfaces, often studied using photoelectron spectroscopy (PES). MHP films, containing organic cations, are susceptible to surface modifications under common experimental conditions, necessitating careful analysis. This study examines the effects of argon gas cluster ion beam (GCIB) sputtering, considered gentler and more suitable for depth‐profiling than standard argon ion sputtering, on methylammonium lead iodide using PES. Long‐term exposure to argon clusters with 3.2 and 1.5 eV per Ar atom causes significant degradation, including cation loss and metallic lead formation. However, short‐term exposure (<60 min) at 1.5 eV per Ar atom effectively reduces surface contamination without noticeable degradation, allowing access to intrinsic electronic properties. This gentle cleaning reveals a 220 meV energy difference between the contaminated surface and the valence band onset of the intrinsic MHP potentially improving energy level alignment with electron transport layers. These results demonstrate that low energy GCIB sputtering can serve as a non‐destructive surface cleaning method, enhancing PES investigations and supporting fundamental device studies of MHPs.