Wide-Range Tuning of Insulator–Metal Transition via Microstructure and Defect Engineering of Sputtered VO ₂ Thin Films

Vanadium dioxide (VO2), a correlated oxide with intrinsically coupled electronic and structural phase transitions, is a promising candidate for smart coatings and advanced electronics. Here, we demonstrate RF magnetron-sputtered VO2 thin films grown on Si (001), amorphous quartz, and c-cut α-Al2O3 substrates under varying sputtering powers. By engineering strain and microstructure, we achieve broad-band modulation of the metal–insulator transition (MIT) spanning more than 20 °C near room temperature. Nanocrystalline VO2 films on Si and quartz exhibit tailored polycrystalline microstructures, while epitaxial VO2 layers on c-cut α-Al2O3 display pronounced out-of-plane compression. Our findings reveal that epitaxial strain dominates Tc tuning in VO2 (020)/c-cut α-Al2O3 systems, whereas microstructural effects govern transport in textured VO2 films with preferred (011) orientation on Si and quartz. The results are supported by X-ray diffraction, Raman spectroscopy, and electron microscopic techniques. Crucially, precise control of strain and microstructure is realized through sputtering power, offering a scalable pathway for VO2-based functional devices.