Direct patterning process for tungsten trioxide nano-to-micro structures

Compared to conventional and complex processes, including deposition, photolithography, and plasma-etching processes, WO₃ nano-to-micro structures were successfully fabricated using direct imprinting process using WO₃ nanoparticle-dispersed resin and consecutive annealing on any substrates in a simpler and more cost-effective manner. WO₃ nanoparticle dispersed resins with various concentrations were evaluated for direct imprinting of WO₃. The pattern fidelity and the surface morphology of imprinted WO₃ nano-to-micro structures were characterized with field emission SEM. X-ray diffractionpattern was used to investigate the effect of annealing process on crystallinity of WO₃ nano-to-micro structures. The crystal structure of imprinted WO₃ was transformed from a hexagonal phase into a monoclinic phase by annealing. Optical transmittance of WO₃ structures were also investigated using UV-vis spectroscopy. It was confirmed that diffused transmittance of WO₃ structures could be increased up to 70% at 550 nm of wavelength without noticeable reduction of total transmittance, which is potentially applicable in the field of optoelectronic devices. Photo-electrochemical cells made of imprinted WO₃ structure were properly operated.