Evaporation of Tetrapod ZnO Nanostructures and Its Influence on the Field-Emission Performance

The ZnO cathode is a promising electron source due to its excellent field-emission performance. In this letter, we investigate the evaporation characteristics of the field emitters in a screen-printed ZnO cathode by a quadrupole mass spectrometer, energy-dispersive X-ray, and scanning electron microscopy. As the experiments show, the oxygen and zinc start to be evaporated if the temperature is higher than 1273 K. The quantity of evaporative materials increases with the increment of temperature, and the quantity of evaporated oxygen is much larger than that of zinc. The evaporations of oxygen and zinc have considerable effects on the field-emission properties of the ZnO cathode, particularly the turn-on field, the threshold electric field, and the emission current density. Therefore, the evaporation of field emitters is an important factor for the stability of the field-emission current.