Field emission characteristics of ruthenium dioxide nanorods

摘要

The effects of post-thermal treatment and rod diameter on the field emission (FE) properties of RuO_2 nanorod films are reported. The FE properties of RuO_2 nanorods with pyramidal tips have been studied on samples of two average rod diameters, 48 and 35 nm. Both of them exhibit a transient behaviour in emission current under a fixed electric field. Thermal annealing at 400 and 500 deg C generally improves the FE characteristics in lowering the emission barriers of nanorods, as manifested by a decrease in the turn-on field, the threshold field, the slope of the Fowler-Nordheim plot, and the time-span of the transient period. Reduction in emission barrier appears to be particularly evident for the 35 nm nanorods. Yet 500 deg C annealing also degrades the emission current stability of 35 nm nanorods. The standard deviation of emission current density of 35 nm nanorods after 500 deg C annealing is around 44 percent. On the other hand, both specimens after 400 deg C annealing display a much more stable emission current density, whose fluctuations are 26 percent of their average values. The transient period is regarded as a consequence of gas molecules being desorbed from the RuO_2 tips during emission, resulting in a reduction of the emission barrier. Thermal annealing weakens the bonding between the adsorbed gas and the tip surface, and facilitates the gas desorption and electron tunnelling processes.