Second harmonic generation in microcrystallite films of ultrasmall Si nanoparticles

We dispersed crystalline Si into a colloid of ultrasmall nano particles (∼1 nm), and reconstituted it into microcrystallites films on device-quality Si. The film is excited by near-infrared femtosecond two-photon process in the range 765–835 nm, with incident average power in the range 15–70 mW, foc...

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Bibliographic Details
Published in:Applied physics letters 2000-12, Vol.77 (25), p.4086-4088
Main Authors: Nayfeh, M. H., Akcakir, O., Belomoin, G., Barry, N., Therrien, J., Gratton, E.
Format: Article
Language:English
Subjects:
CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS
COLLOIDS
DIMERS
HARMONIC GENERATION
PHYSICS
RADIATIONS
SILICON
WAVELENGTHS
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Summary:We dispersed crystalline Si into a colloid of ultrasmall nano particles (∼1 nm), and reconstituted it into microcrystallites films on device-quality Si. The film is excited by near-infrared femtosecond two-photon process in the range 765–835 nm, with incident average power in the range 15–70 mW, focused to ∼1 μm. We have observed strong radiation at half the wavelength of the incident beam. The results are analyzed in terms of second-harmonic generation, a process that is not allowed in silicon due to the centrosymmetry. Ionic vibration of or/and excitonic self-trapping on novel radiative Si–Si dimer phase, found only in ultrasmall nanoparticles, are suggested as a basic mechanism for inducing anharmonicity that breaks the centrosymmetry.
ISSN:0003-6951
1077-3118
DOI:10.1063/1.1334945