Influence of RuO2 nanoparticles on electron emission from carbon nanotubes

The authors studied the influence of RuO2 nanoparticles attached to multiwalled carbon nanotube (MWCNT) emitters on field emission. The threshold field, corresponding to 10mA∕cm2, was reduced 30% to ∼0.90V∕μm after attaching the particles. However, the particles deteriorated the stability of field emitters to some extent, especially in the high emission-current-density region of several A∕cm2. The maximum emission-current density was limited to a lower current region compared with field emitters without RuO2. This can be explained reasonably by considering the vaporization of RuO2 particles that frequently causes significant self-ion-sputtering during strong emission because of the large contact resistance between the particles and MWCNTs. This explanation was experimentally proved by measuring the reduction of field-enhancement factor with the elapsed-emission time. This reduction is quicker for emitters with RuO2 than for emitters without RuO2. Experimental data also show that the standard deviation of Fowler-Nordheim plots for field emitters can be used to judge their stability and lifetime—a value of ∼5×10−3 suggests stable performance for our emitters.