The field emission properties of double-walled carbon nanotubes (DWCNTs) were remarkably improved by decorating their surface with ruthenium (Ru) metal nanoparticles. The Ru nanoparticles were attached effectively on the surface of DWCNTs via a chemical procedure. The Ru-decorated DWCNTs showed lower turn-on voltage, higher emission current density, and improved emission uniformity compared with pristine DWCNTs. The effect of Ru nanoparticles on the work function and density of states was evaluated by the first-principles calculation. The enhanced field emission properties of Ru-DWCNTs were mainly attributed to the Ru nanoparticles which increased the field enhancement factor and the density of emission sites. Our results indicate that the Ru-decorated DWCNTs can be used as an effective field emitter for various field emission devices.
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