Role of sp2 phase in field emission from nanostructured carbons

It is shown that ${\mathrm{sp}}^2$ phase organization plays an important role in the field emission from nanostructured carbons. Emission is found to depend on the cluster size, anisotropy, and mesoscale bonding of the ${\mathrm{sp}}^2$ phase, and the electronic disorder. It is found by Raman spectroscopy that increasing the size of ${\mathrm{sp}}^2$ clusters in the 1–10 nm range improves emission. Anisotropy in the ${\mathrm{sp}}^2$ phase orientation can help or inhibit the emission. ${\mathrm{sp}}^2$ clusters embedded in the ${\mathrm{sp}}^3$ matrix or electronic disorder induced by localized defects oriented in the field direction can provide a local field enhancement to facilitate the emission.