In situ and nanoscale spectroscopic analysis of soft X-ray-induced transformations in indium nitrate films

Photoinduced chemical transformations in inorganic metal-oxide systems play a central role in applications where photon exposure modifies chemical bonding and local structure. However, the underlying reaction pathways remain difficult to resolve because multiple processes occur simultaneously during irradiation and transient chemical states are rarely accessible by conventional ex situ analyses. In this study, we systematically investigate the photon-induced chemical evolution of indium nitrate sol–gel films using a combination of in situ and spatially resolved spectroscopic techniques. Time-resolved in situ X-ray photoelectron spectroscopy under soft X-ray irradiation enables direct monitoring of ligand dissociation, oxide network formation, and defect-related states. Complementary Fourier-transform infrared spectroscopy (FT-IR) reveals vibrational changes associated with the degradation of nitrate and hydroxyl ligands. Furthermore, scanning photoelectron microscopy (SPEM) provides nanometer-scale chemical mapping of irradiation-induced modifications. By combining temporal and spatial analyses, we identify characteristic transformation thresholds and directly visualize photon-induced nanoscale line patterns. These findings provide mechanistic insight into bond rearrangement and defect evolution in indium-based oxide precursors and establish a real-time, nanoscale-resolved analytical framework for elucidating photochemistry in metal-oxide systems.