Microscopic processes of defects formation in molybdenum oxide induced by energetic heavy ions

Ion-solid interaction leads to significant modifications in both the surface and bulk of materials, providing a precise route for nanoscale defects control in functional oxides. In this work, we investigate the effects of MeV Au-ion irradiation on (Formula presented) (Formula presented) -MoO (Formula presented) (Formula presented). Structural, optical, and chemical analysis reveal defect generation manifested as oxygen vacancy formation, suboxide phases, and amorphization, leading to significant changes in the optical properties. Depth-resolved defect profiling using Doppler broadening variable-energy positron annihilation spectroscopy further shows an enhancement of open-volume defects at the near-surface region of all irradiated films, while the unirradiated sample exhibits a slight defect depletion beneath the top 10–20 nm. Across the film thickness, irradiated samples display an almost depth-independent defect distribution, indicating homogeneous defect formation within the ion-affected bulk. The observed structural and optical changes are studied in terms of the demonstrated microscopic view of ion-induced defects.