Scanning field emission from patterned carbon nanotube films

The investigation of the field emission (FE) properties of carbon nanotube (CNT) films by a scanning anode FE apparatus, reveals a strong dependence on the density and morphology of the CNT deposit. Large differences between the microscopic and macroscopic current and emission site densities are observed, and explained in terms of a variation of the field enhancement factor β. As a consequence, the emitted current density can be optimized by tuning the density of CNTs. Films with medium densities (on the order of ${10}^7 {\mathrm{emitters/cm}}^{\mathrm{2}},$ according to electrostatic calculations) show the highest emitted current densities.