Negative differential resistance in single-wall carbon nanotube network

The current-voltage (I-V) characteristic of single-wall carbon nanotube (SWNT) network was investigated at low temperatures. At T∼ 1.6K, S-shaped negative differential resistance (NDR) was observed, which was systematically examined under the variation of temperature, magnetic field in transverse direction and distances between probes. S-shaped NDR was explained by the nondestructive impact ionization of carriers and the resulting rmation of inhomogeneous spatial structures such as high-current filaments. Critical electric field for impact ionization was estimated to be about IV/ cm.