We report the synthesis of ZnO tetrapods using an atmospheric-pressure microwave plasma jet system, and analyze their size-dependent photosensing properties. The sizes of the synthesized ZnO tetrapods are controlled by changing the applied plasma power and the distances of their collection sites from the plasma-generation region. The results of high-magnification transmission electron microscopy, X-ray diffractometry, and Raman spectroscopy indicate that the synthesized ZnO tetrapods exhibit high crystallinity. In general, the size of ZnO tetrapods increases as the plasma power and distance from the plasma-generation region increase. A photosensing device is fabricated for comparative characterization by dispersing the synthesized ZnO tetrapods in deionized water and spray coating them. The results of the sensing characterization using ultraviolet light illumination show that larger ZnO tetrapods increase the photocurrent, improve the sensitivity, and reduce the sheet resistance of the device.

Keywords: ZnO tetrapod, Atmospheric plasma jet, Spray coating, Photosensing property