Subsurface Characteristics of Metal-Halide Perovskites Polished by Argon Ion Beam

TL;DR

This study investigates how argon ion beam polishing affects the subsurface properties of metal-halide perovskites, revealing localized modifications that influence aging behavior while preserving overall bulk integrity.

Contribution

It combines experimental and simulation approaches to characterize subsurface changes caused by argon ion beam polishing in perovskites, highlighting implications for microstructural analysis.

Findings

Atomic displacements and local heating occur in subsurface MAPbI3

Lead-rich, iodine-deficient surface promotes phase segregation

Bulk material integrity remains largely unaffected

Abstract

Focused ion beam (FIB) techniques have been frequently used to section metal-halide perovskites for microstructural investigations. However, the ion beams directly irradiated to the sample surface may alter the properties far different from pristine, potentially leading to modified deterioration mechanisms under aging stressors. Here, we combine complementary approaches to measure the subsurface characteristics of polished perovskite and identify the chemical species responsible for the measured properties. Analysis of the experimental results in conjunction with Monte Carlo simulations indicates that atomic displacements and local heating occur in the subsurface of methylammonium lead iodide (MAPbI3) by glazing Ar+ beam irradiation (15 nm by 4 kV at 3 degree). The lead-rich, iodine-deficient surface promotes rapid phase segregation under thermal aging conditions. On the other hand, despite the subsurface modification, our experiments confirm the rest of the MAPbI3 bulk retains the material integrity. Our observation supports that polished perovskites could serve in studying the properties of bulk or buried junctions far away from the altered subsurface with care.