A study of methanol dilution and substrate temperature on phase transition dynamics and functional properties of V2O5 thin films for sustainable technologies

In this work, V 2 O 5 thin films were deposited on glass substrates using a nebulised spray pyrolysis technique to systematically investigate the influence of methanol-to-precursor dilution ratios (1:1, 2:1, and 3:1) and substrate temperatures (300 °C, 400 °C, and 500 °C) on their structural, optical, and electrical properties. High-resolution X-ray diffraction revealed an amorphous-to-orthorhombic α-V 2 O 5 phase transition at 400 °C, followed by the formation of β-V 2 O 5 at 500 °C, with the 2:1 dilution ratio exhibiting the highest crystallinity. Surface morphology analysis confirmed temperature-driven grain growth and enhanced surface ordering at elevated temperatures. FTIR-ATR spectra verified the presence of V = O and V–O–V vibrations. Optical studies showed that the energy bandgap could be tuned between 2.44 eV and 3.18 eV by varying dilution ratio and substrate temperature, while photoluminescence analysis revealed multiple emission bands associated with interband transitions and defect-related states. Overall, the results highlight that controlled precursor dilution and substrate temperature provide an effective route for tailoring the optoelectronic properties of V 2 O 5 thin films, making them suitable for gas sensing, optoelectronic applications and sustainable technologies.