Field emission from carbon nanotube (CNT) arrays and triode test of single CNT columns

Vertically aligned carbon nanotube (CNT) arrays were grown on highly-doped silicon substrates with patterned iron catalyst by means of hot-filament chemical vapor deposition (HFCVD). CNT columns of diameter Ø = 250 μm and different height (h = 70 or 350 μm) formed quadratic arrays with a pitch of 650 μm. Single CNT columns of Ø = 1.5 mm and h = 250 μm were also fabricated. Fairly aligned and efficient field emission (FE) was obtained from the CNT arrays at onset fields for 1 nA of ~2 V/μm. Maximum current values up to 600 μA at 15 V/μm were achieved for selected columns of both heights. Thermal glow effects were often visible during current processing just before destruction of the CNT columns. The FE triode tests of single CNT columns yielded anode-cathode current ratio up to 97 % at a gate (anode) voltage of 247 (2500) V.