Enhanced field emission of open-ended, thin-walled carbon nanotubes filled with ferromagnetic nanowires

A general strategy for in situ synthesis of open-ended, thin-walled carbon nanotubes (CNTs) filled with long ferromagnetic (FeNi, FeCo, FeCoNi, etc.) nanowires is proposed. The key feature of this strategy is the introduction of Cl-contained benzene (e.g. trichlorobenzene) as carbon precursor. Size-dependent etching effect of Cl radicals on the sidewalls of CNTs is proved by theoretical calculations. As-prepared thin-walled FeNi-filled CNTs (FeNi–CNTs) show much lower turn-on field of 0.30 V/μm (at 10 μA/cm2) and lower threshold field of 0.65 V/μm (at 1.0 mA/cm2) than those of thick-walled counterparts. Moreover, as-prepared thin-walled FeNi–CNTs show good field-emission stability at a low vacuum level (10−6 Torr). The enhanced field-emission performance can be attributed to a combined contribution of open-end tips, thinner sidewalls and metal nanowire fillings.