Ultra-low-threshold field electron emission from pillar array of aligned carbon nanotube bundles

We observed the field electron emission of the technologically useful current density of 10mA/cm(2) at an extremely low threshold electric field (E-th) of 1.0 V/mum, from an array of pillars of aligned carbon nanotube bundles, which were grown on a Si substrate by thermal chemical vapor deposition. Adjusting the distance between the neighboring pillars (R) and the pillar height (H) to the optimal condition (R/H = 2) can effectually enhance the field concentration, resulting in a highly efficient electron emission. The obtained E-th is 1/2-1/3 times lower than the best values that have been reported to date.