Characterization of RuO2 nanocrystals deposited on carbon nanotubes by reactive RF sputtering

RuO₂ nanocrystals (NCs) were deposited on carbon nanotubes (CNTs) by reactive RF magnetron sputtering using a Ru target under different conditions. Their surface morphology, structural, spectroscopic and field emission (FE) properties were studied using field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM), Raman spectroscopy, and a home made high vacuum FE measurement system. FESEM micrographs showed that the surface morphology of the as-deposited RuO₂ varied from nanoparticles-like to tube-like NCs as the oxygen flux increased from 2 to 10 sccm. The TEM image of RuO₂-coated CNTs revealed that uniform distribution and random direction of RuO₂ NCs had been deposited on the surface of the CNTs. The red-shifts of the peak positions and broadening of linewidths of the Raman features were attributed to both the size and residual stress effects. The FE characteristics revealed a low operating electric field and stable emission current in the RuO₂-coated CNTs.