Author/Authors :
Gianluca Galimberti and Fulvio Parmigiani، نويسنده , , Stefania Pagliara، نويسنده , , Stefano Ponzoni، نويسنده , , Stefano Dal Conte، نويسنده , , Federico Cilento، نويسنده , , Gabriele Ferrini، نويسنده , , Stephan Hofmann، نويسنده , , Muhammad Arshad، نويسنده , , Cinzia Cepek، نويسنده , , Fulvio Parmigiani، نويسنده ,
Abstract :
Using time-resolved reflectivity measurements on unaligned and aligned bundled single-wall carbon nanotubes with a pump energy of 1.55 eV, quasi-resonant with the second Van Hove singularity of semiconducting tubes, a positive sign of the transient reflectivity is detected in unaligned nanotubes. In contrast a negative sign is detected in aligned nanotubes. This discovery addresses a long-standing question showing that in unaligned nanotubes the stronger intertube interactions favor the formation of short-lived free charge carriers in semiconducting tubes. A detailed analysis of the transient reflectivity spectral response shows that the free carriers in the photo-excited state of semiconducting tubes move towards metallic tubes in about 400 fs.
