2-D localization in single wall carbon nanotube network synthesized by arc-plasma method

Resistivity ρ(T) and magnetoresistance (MR), ((ρ(H)-ρ(H=0))/ρ(H=0), of the entangled single wall carbon nanotube (SWCN) network are studied. The temperature dependence of the resistivity shows the negative dρ/dT from T=4.2K to 300K, which fits well to the 2-dimensional variable range hopping (VRH) (ρ(T)=ρ0exp((T0/T)1/3)) formula with T0= 259.2 K. The overall MR shows a negative H2 behavior at low magnetic field. At T≤3.8K and high magnetic field, the negative MR turns to be positive. The positive MR becomes saturating for H>10 Tesla. The negative MR with a positive upturn can be decomposed into a positive contribution from the 2-dimensional spin-dependent VRH and a negative contribution from the 2-dimensional weak localization (WL). Moreover we report the interesting chain-like ring structures found from the by-products of SWCNs synthesized by the arc-plasma method.