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

Abstract

Abstract 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 α -MoO 3 . 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.