Field emission properties from double walled carbon nanotubes produced by a catalytic CVD

High quality DWNTs (double-walled carbon nanotubes) was produced by a catalytic CVD. The field emission was measured using parallel-plate geometry with a gap distance of 270 /spl sim/ 370 /spl mu/m under a 2 /spl times/ 10/sup -7 /Torr. The turn-on electric field of DWNTs was about 1.7 /spl sim/ 3.5 V//spl mu/m at /spl sim/ 1.0 /spl times/ 10/sup -7/ mA/cm/sup 2/ and the current density of DWNTs was about /spl sim/ 20mA/cm/sup 2/ at the applied electric field of /spl sim/ 8V//spl mu/m. The lifetime indicated good stability for 20 hours when constant DC voltage applied at high current density of /spl sim/ 1.0 /spl times/ 10/sup -3/ A/cm/sup 2/.