Andrea Fasoli1, Alan Colli2, Faustino Martelli3, Simone Pisana1, Ping Heng Tan4, and Andrea C. Ferrari1 ()
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1 Department of Engineering, University of Cambridge, Cambridge CB3 0FA, UK2 Nokia Research Centre, Broers Building (East Forum), Cambridge CB3 0GT, UK3 Istituto per la Microelettronica e i Microsistemi del CNR, 00133 Rome, Italy4 SKLSM, Institute of Semiconductors, Chinese Academy of Sciences, Beijing 100083, China
We present temperature and power dependent photoluminescence measurements on CdSe nanowires synthesized via vapor-phase with and without the use of a metal catalyst. Nanowires produced without a catalyst can be optimized to yield higher quantum efficiency, and narrower and spatially uniform emission, when compared to the catalyst-assisted ones. Emission at energies lower than the band-edge is also found in both cases. By combining spatially-resolved photoluminescence and electron microscopy on the same nanowires, we show that catalyst-free nanowires exhibit a low-energy peak with sharp phonon replica, whereas for catalyst-assisted nanowires low-energy emission is linked to the presence of nanostructures with extended morphological defects.