Defect-induced Nb 2 O 5 thin films were fabricated by RF magnetron sputtering through controlled interruptions of O 2 flow to investigate how oxygen deficiency affects structural, optical, electrical, and photocatalytic properties. Oxygen interruption times from 10 to 90 s generated oxygen-deficient regions within a Nb 2 O 5 matrix. As-samples are amorphous, while annealing at 500 °C under argon promoted crystallization into the TT-Nb 2 O 5 phase, accompanied by systematic changes in crystallite size, dislocation density, and micro-strain. Optical analysis revealed bandgap narrowing (∼3.33–3.20 eV) and increased Urbach energy after annealing, indicating defect-related disorder. Under UV excitation, short interruption times (10–20 s) enhanced carrier generation in as-samples through shallow donor-like defects, whereas longer interruptions favored deep traps that limited photoresponse. After annealing, longer interruptions (70–90 s) improved photoconductivity through defect redistribution and activation of defect-rich regions, thereby enhancing conductivity. Conversely, methylene blue degradation decreased after annealing, revealing decoupling between bulk electronic transport and surface photocatalytic activity. • Nb 2 O 5 thin films with oxygen-deficient regions were obtained by O 2 flow modulation during sputtering. • Oxygen vacancies and defect-related states govern photoinduced charge transport. • Annealing promotes defect redistribution and activates conductive oxygen-deficient regions. • Surface and bulk defect effects influence carrier dynamics under air and vacuum. • Photoconductivity enhancement occurs independently of photocatalytic activity.
Escaliante et al. (Fri,) studied this question.