Electrical Properties and Reliability of ZnO-Based Nanorod Current Emitters

The fabrication, optical, and field emission properties of ZnO-based nanorod emitters were studied. Ga-doped ZnO nanorods combined with the formation of tip structure on top of a ZnO nanorod by oxygen plasma treatment are employed to improve the field emission properties of the nanorod emitters. By either of these two methods, the nanorod emitters exhibit significantly reduced turn-on field and enhanced field-emission factor. The morphology, crystal structure, and composition of all the nanorods used for making emitters are characterized by a scanning electron microscopy, X-ray diffraction, and energy dispersive X-ray spectrometer. The nanorods exhibit the highly preferred c -axis orientation single crystal structure. The photoluminescence spectra indicate the nanorods have better crystalline structure after doping and oxygen plasma treatment. Combining gallium doping process (Ga/Zn molar ratio of 1% in solution) and oxygen plasma treatment (etching time of 60 s), the tip-structured GZO nanorod emitters with tip angle of 100° have a turn-on field of 1.99 V/μm under a current density of 1 μA/cm², field enhancement factor of 2465, and stable operation over 2 × 10⁴ s. Such improved field emission properties are attributed to decreased work function and sharp nanotips morphology. In addition, the GZO nanorod emitters with tip structure are successively and stably operated between 25°C and 100°C over 3000 s based on the high-temperature field emission measurement results. They have high potential for practical applications in flat panel display and light emitting device in the future.