Environmental effects on the carrier dynamics in carbon nanotubes

Carrier dynamics is investigated in both luminescent and nonluminescent samples of single wall carbon nanotubes-obtained by laser ablation-by means of two-color pump-probe experiments. The recombination dynamics is monitored by probing the transient photobleaching observed on the interband transitions of semiconducting nanotubes. Interband and intersubband relaxation times are about one order of magnitude slower in isolated nanotubes than in ropes of nanotubes bringing evidence of the environmental influence on the carrier dynamics. The relaxation dynamics is nonexponential and is interpreted as a consequence of the inhomogeneity of the sample. Slow components up to 250 ps are measured which is significantly greater than values previously reported in HiPCO nanotubes. These observations show the great dependence of the electronic properties of carbon nanotubes on the synthesis method and on their environment