Study on the fabrication of vertical/complex metal oxide nanostructure for UV sensor and solar water splitting

Abstract

Metal oxide nanostructure has been numerous studied during several decades for the applications in microelectronics, artificial skin sensor, transparency conducting electrode, energy devices and displays. Among various metal oxide nanostructures, especially, 1-dimensional nanostructure has been large interested due to its large surface to volume ratio and ballistic transport property. These features provide several unique aspects of their physical, chemical, optical and mechanical properties compared to the bulk state. While those particular properties, in this study, optical property of metal oxide nanostructure was noticed. Typically, metal oxide materials have energy band gap that can be modify through the shape of material structure and doping. Accordingly, vertical/complex metal oxide nanostructure materials were fabricated and examined for the usable functions in optoelectronic devices and applications. For the growth of vertical metal oxide nanostructure, inkjet printing has been introduced for direct selective patterning. Direct selective nanowire array growth using inkjet printing of Zn acetate precursor ink patterning and subsequent hydrothermal ZnO local growth without nozzle clogging problem which frequently happens in nanoparticle inkjet printing. The proposed process can directly grow ZnO nanowires in any arbitrary patterned shape and it is basically very fast, low cost, environmentally benign, and low temperature. Therefore, Zn acetate precursor inkjet printing based direct nanowire local growth is expected to give extremely high flexibility in nanomaterial patterning for high performance electronics fabrication especially at the development stage. As a proof of concept of the proposed method, ZnO nanowire network based field effect transistors and UV photo-detecctors were demonstrated by direct patterned grown ZnO nanowires as active layer. In addition, for the complex metal oxide nanostructure, facial fabrication process for hydrothermal growth of $\alpha -Fe_2O_3$ (hematite) and following photoreduction of Ag nanoparticles were investigated. The complex $\alpha -Fe_2O_3/Ag$ nanostructure brings enhanced photon absorb efficiency. The suggested process and material were evaluated by SERS, photoluminescence, cyclic voltammetry. Subsequently, the fabricated complex nanostructure was demonstrated in the photoelectrochemical cell as a photoanode.