Field emission characteristics of metal nanoparticle-coated carbon nanowalls

Metal nanoparticles are deposited on nitrogen-incorporated carbon nanowalls (CNWs) using Ag, Au, In, and Mg as metal species for enhancing field emission. Morphology, coverage, chemical composition, and crystallinity of the metal coatings on CNW surfaces are examined by varying nominal thickness of metals within 10 nm. The emission characteristics reveal that coating CNWs with any metal species lowers emission turn-on fields and thus increases emission efficiency. The inverse dependence of field enhancement factor and turn-on field upon nominal thickness of metals confirms that additional field amplification at metal nanoparticles governs emission efficiency regardless of work functions of the metals. The Ag-coated CNWs retain the highest current density for long-time emission at a constant applied field, while the non-coated CNWs have higher emission stability and a larger time constant of current degradation than the metal-coated ones.