Annealing Impact on the Optical Properties of MoO3 Thin Films

Molybdenum trioxide (MoO3) thin films were synthesized via the Chemical Vapor Deposition (CVD) method and annealed at different temperatures (800 °C to 950 °C) to analyze their temperature-dependent optical properties. The films were analyzed by UV-Vis spectroscopy, Tauc analysis, and photoluminescence (PL) spectroscopy. Absorption spectra revealed a progressive shift in the absorption edge with enhancing annealing temperature, which suggests better crystallinity and optical quality. Tauc plots indicated the decrease in optical band gap from 3.25 eV at 800 °C to 3.10 eV at 950 °C, owing to improved grain growth and low defect density. Transmittance measurements indicated that the films retained high transparency within the visible region, with slight reduction at high temperatures because of increased thickness of the film and surface roughness. PL spectra had emission peaks around 415 nm, 427 nm, and 536 nm, related to oxygen vacancies and defect-related recombination processes. These results reveal the pivotal role of annealing temperature in the tuning of optical properties of MoO3 thin films, indicating them as ideal candidates for optoelectronic and photonic device applications.