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Probing ultrafast carrier dynamics, nonlinear absorption and refraction in core-shell silicon nanowires

Kumar, Sunil and Khorasaninejad, M and Adachi, MM and Karim, KS and Saini, SS and Sood, AK (2012) Probing ultrafast carrier dynamics, nonlinear absorption and refraction in core-shell silicon nanowires. In: PRAMANA-JOURNAL OF PHYSICS, 79 (3). pp. 471-481.

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Official URL: http://dx.doi.org/10.1007/s12043-012-0337-y

Abstract

We investigate the relaxation dynamics of photogenerated carriers in silicon nanowires consisting of a crystalline core and a surrounding amorphous shell, using femtosecond time-resolved differential reflectivity and transmission spectroscopy at 3.15 eV and 1.57 eV photon energies. The complex behaviour of the differential transmission and reflectivity transients is the mixed contributions from the crystalline core and the amorphous silicon on the nanowire surface and the substrate where competing effects of state-filling and photoinduced absorption govern the carrier dynamics. Faster relaxation rates are observed on increasing the photogenerated carrier density. Independent experimental results on crystalline silicon-on-sapphire (SOS) help us in separating the contributions from the carrier dynamics in crystalline core and the amorphous regions in the nanowire samples. Further, single-beam z-scan nonlinear transmission experiments at 1.57 eV in both open- and close-aperture configurations yield two-photon absorption coefficient beta (similar to 3 cm/GW) and nonlinear refraction coefficient gamma (-2.5 x 10 (-aEuro parts per thousand 4) cm(2)/GW).

Item Type: Journal Article
Additional Information: Copyright for this article belongs to Indian Academy of Sciences
Keywords: Silicon;nanowires;femtosecond;ultrafast spectroscopy;nonlinear optical coefficients
Department/Centre: Division of Physical & Mathematical Sciences > Physics
Date Deposited: 12 Nov 2012 11:05
Last Modified: 12 Nov 2012 11:05
URI: http://eprints.iisc.ernet.in/id/eprint/45327

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