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The photoinduced charge transfer mechanism in aligned and unaligned carbon nanotubes |
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| Authors: | Gianluca Galimberti Stefania Pagliara Stefano Ponzoni Stefano Dal Conte Federico Cilento Gabriele Ferrini Stephan Hofmann Muhammad Arshad Cinzia Cepek Fulvio Parmigiani |
| Affiliation: | aDipartimento di Matematica e Fisica, Università Cattolica del Sacro Cuore, I-25121 Brescia, Italy;bDipartimento di Fisica, Università di Pavia, I-27100 Pavia, Italy;cDipartimento di Fisica, Università di Trieste and Laboratorio Nazionale TASC, AREA Science Park, Basovizza, Trieste I-34012, Italy;dDepartment of Engineering, University of Cambridge, Cambridge CB3 0FA, UK;eICTP, Strada Costiera 11, I-34151 Trieste, Italy;fIstituto Officina dei Materiali - CNR, Laboratorio TASC, Area Science Park, Basovizza, I-34149 Trieste, Italy;gDipartimento di Fisica, Università di Trieste and Sincrotrone Trieste, I-34012 Basovizza, Trieste, Italy;hZernike Institute for Advanced Materials, University of Groningen, The Netherlands;iNational centre for Physics Quaid-i-Azam University Islamabad, Pakistan |
| 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. |
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