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Published December 2013 | public
Journal Article

Scanning near-field optical microscopy on dense random assemblies of metal nanoparticles


Plasmonic absorption enhancement by metal nanoparticles strongly relies on the local electric field distributions generated by the nanoparticles. Therefore, here we study random assemblies of metal nanoparticles as they are widely considered for solar cell application with scanning near-field optical microscopy. A collective scattering behavior is observed despite a resolution on the particle size. We find variations in scattering intensity on a length scale several times larger than in the topography. FDTD (finite-difference time domain) simulations show the impact of irregularities and size variations on the scattering behavior. An understanding of the plasmonic scattering behavior at the nanometer scale will support the successful application of nanoparticles for absorption enhancement in thin-film solar cells.

Additional Information

© 2013 IOP Publishing Ltd. Received 10 July 2013, accepted for publication 16 October 2013. Published 4 November 2013. We thank A Leenher, R Palla and D Turner-Evans for technical support with the SNOM and scientific exchange. V Brar and S Kim are acknowledged for providing FIB and SEM on the tips, respectively, M Jang for computer support and the MMRC (Caltech) for access to the SNOM. M Schmid also thanks M Kirsch for In_2O_3:Mo sputtering and R Bartmann for discussion. The work of J Grandidier and H A Atwater was supported by the Department of Energy 'Light-Material Interactions in Energy Conversion' Energy Frontier Research Center under Grant DE-SC0001293. M Schmid acknowledges support from the Initiative and Networking fund of the Helmholtz Association for the Young Investigator Group VH-NG-928.

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