Metal Oxide Nanostructures for High-Performance Ultraviolet Photodetection

These predictions are validated using FSP-synthesised hydroxyapatite (HAp) films, demonstrating close agreement between simulated and experimental porosity evolution and establishing a predictive foundation for morphology control.</p><p dir="ltr">Building on this understanding, a metal oxide to polymer interface is introduced through controlled poly(methyl methacrylate) (PMMA) infiltration of zinc oxide (ZnO) nano-micro clusters (NMCAs), enabling high-performance UV photodetection at an ultra-low bias (0.1 V).

The polymer simultaneously passivates surface defects, modulates charge transport pathways, and enhances light trapping within the porous network. This results in a substantial responsivity enhancement while revealing a fundamental trade-off between carrier transport and defect passivation at higher polymer loadings. The optimised ZP4 device achieved a responsivity of 3.76 A·W-1·V-1 at 0.1 V, approximately 8.5 times that of pristine ZnO, with rise and decay times of 90 and 150 s, respectively.</p><p dir="ltr">Leveraging these insights, device functionality is enhanced through using ZnO-based UV photodetectors.

A precisely controlled ZnO-on-ZnO hierarchical design strategy demonstrates that a sequential overcoating of FSP deposited ZnO on NMCAs can precisely tune light scattering, NMCA connectivity, and oxygen-mediated surface processes. Rather than monotonically improving performance, an optimal intermediate structure emerges, delivering high responsivity, strong current contrast, and stable low-voltage operation at 10 s ZnO deposition duration over the NMCAs.

The optimised Z10 device exhibited a peak responsivity of 910 mA·W-1 at 340 nm and 0.5 V, a maximum current contrast of 697, and rise and decay times of 35.7 and 40.0 s, respectively, while maintaining stable switching over 40 on/off cycles during 240 min of testing.</p><p dir="ltr">Building on this understanding, FSP processing parameters and post-deposition solvent treatments are experimentally mapped to govern the transformation of dendritic nanocluster (DNC) films into hierarchical NMCAs across multiple oxide systems.

Morphology is shown to be governed not by a single parameter, but by the interplay between FSP conditions, particle sintering, deposition time, and solvent-driven capillary restructuring. Across titanium dioxide (TiO2), silicon dioxide (SiO2), copper oxide (CuO), and cobalt oxide (CoO) systems, height above burner (HAB) emerges as the dominant factor controlling thermal history, particle necking, and porosity, enabling a practical roadmap for tailoring hierarchical architectures.

Together, this work establishes a unified framework linking nanoparticle polydispersity, hierarchical film formation, and device-level performance. By connecting particle-scale transport physics to mesoscale morphology and ultimately to optoelectronic functionality, it provides a scalable and predictive pathway for designing high-performance, low-power nanostructured devices for enhanced UV photodetection.</p>