Hybrid flame-assisted plasma-enhanced chemical vapor deposition strategy for scalable and structurally tunable ZrO₂ thin films

Zirconium dioxide (ZrO₂) thin films are critical materials owing to their thermal stability, mechanical durability, and optical transparency enabling applications in photonic, sensing, and electronic devices. However, achieving uniform deposition via plasma-enhanced chemical vapor deposition (PE-CVD) has remained challenging due to poor nucleation on untreated substrates. In this work, we demonstrated a hybrid strategy that integrated flame spray pyrolysis (FSP) seeding prior to PE-CVD to enhance nucleation. We systematically investigated the effect of seed composition, seeding duration, substrate type, growth parameters (temperature and plasma power), and post-deposition calcination on film morphology and structure. We found that oxide-based seeds (ZrO₂, ZnO) promote uniform, continuous, and dense films, whereas noble metals (Au, Pt) lead to sparse and discontinuous nucleation. Under optimized conditions, we obtained a uniform nanostructured ZrO₂ film with particle sizes of 120 ± 0.1 nm and up to 89% transmittance. X-ray diffraction confirmed crystalline tetragonal ZrO₂ with enhanced grain orientation. The hybrid FSP–PE-CVD strategy enables uniform, transparent ZrO₂ thin films with controllable grain size and phase composition. This approach provides a robust platform for scalable oxide film fabrication where optical transparency and morphological precision are critical.