Nanostructured TiO₂ Thin Films for Enhanced Photocatalytic and Solar Cell Applications: A Magnetron Sputtering Approach

Abstract

Titanium dioxide (TiO₂) remains one of the most promising semiconductor materials due to its stability, abundance, and broad applicability in photocatalysis and solar energy conversion. This study reports the fabrication of nanostructured TiO₂ thin films using RF magnetron sputtering and investigates the influence of substrate type and deposition conditions on structural and functional properties. X-ray diffraction revealed that films deposited on glass substrates predominantly exhibited the anatase phase, while sapphire substrates promoted partial rutile formation. Scanning electron microscopy confirmed nanostructured morphologies with average crystallite sizes between 20–35 nm. Optical studies indicated a direct bandgap narrowing to 3.05 eV for sapphire-supported films, compared to 3.20 eV for those on glass, suggesting improved visible light absorption. Photocatalytic efficiency was tested using methylene blue degradation under UV irradiation, where films on sapphire showed nearly 40% higher degradation rate constants than glass-supported films. The improved photocatalytic activity was attributed to better crystallinity and electron-hole separation facilitated by substrate-induced stress. These findings highlight the substrate-dependent tunability of TiO₂ thin films, which can be leveraged for next-generation solar cells and wastewater treatment technologies.