Low-Temperature Deposition of Alumina Films by Ultrasonic Spray Pyrolysis with a Water-Based Precursor

Alumina (Al2O3) is a key material in inorganic and hybrid electronics due to its excellent dielectric, chemical, and thermal stability properties. In this work, we present the first results of alumina films deposited by ultrasonic spray pyrolysis (USP) at low temperatures (40–100 °C) using water as the sole solvent, followed by an annealing step at 100 °C. The films were characterized by SEM, XRD, EDS, and UV-Vis spectroscopy to evaluate their morphology, structure, composition, and optical properties. Preliminary results show an average thickness of approximately 8 µm, with surface features consisting of agglomerates (average particle size ≈ 7.252 µm) distributed over the film. XRD patterns revealed the presence of tetragonal and orthorhombic phases, while EDS confirmed the presence of aluminum and oxygen with slight compositional variations depending on deposition and annealing conditions. UV-Vis absorption spectra exhibited characteristic bands between 259 nm and 263 nm. These results provide a comprehensive understanding of the optical, structural, and morphological behavior of Al2O3 films processed at low temperatures. The motivation for studying these films is to enable more eco-friendly gate oxides for organic MIS structures, as well as functional layers in photonic devices. This approach represents a sustainable and straightforward route for obtaining Al2O3 coatings compatible with temperature-sensitive substrates, paving the way for future applications in hybrid and organic electronics.