Synthesis and field emission properties of Cu-filled vertically aligned carbon nanotubes

Highlights: • First-time growth of Cu-filled carbon nanotube (Cu@VACNT) without extra catalysts. • Subtle evolution on the Cu substrate was vital for synthesizing Cu@VACNTs • Tuning the growth temperature controls the filling of Cu inside the VACNTs. • Superior field emission performance of Cu@VACNT core-shell field emitters. A highly conductive metal core modifies the electronic properties of a carbon shell, offering the possibility of enhancing its field emission (FE) behavior. Herein, a method has been devised to synthesize copper-filled vertically aligned carbon nanotubes (Cu@VACNTs) directly on Cu disks without extra metal catalysts via plasma-enhanced chemical vapor deposition. An ensemble of Cu particles formed on the surface of Cu disks due to surface reconstruction in a reducing environment plays a crucial role in the nucleation and growth of Cu@VACNTs. The filling of Cu inside the VACNTs can be controlled by tuning the growth temperature. The study of FE properties revealed that a conductive Cu-core extending throughout the entire length of the VACNTs could significantly enhance the FE properties of the VACNTs. Excellent FE properties including low turn-on field (E_To = 1.57 V/µm), low threshold field (E_Th = 2.43 V/µm), high field enhancement factor (β = 3061), and high FE stability were observed for the Cu@VACNTs. The enhanced FE properties of the Cu@VACNTs can be accredited to low field screening due to bundled morphology and improved electrical and thermal conductivities offered by the encapsulation of highly conductive Cu nanowires inside the cores of VACNTs.