Field emission characteristics of ruthenium dioxide nanorods

The effects of post-thermal treatment and rod diameter on the field emission (FE) properties of RuO2 nanorod films are reported. The FE properties of RuO2 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 degrees 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 degrees 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 degrees C annealing is around 44%. On the other hand, both specimens after 400 degrees C annealing display a much more stable emission current density, whose fluctuations are 26% of their average values. The transient period is regarded as a consequence of gas molecules being desorbed from the RuO2 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.