Photoexcited Fano interaction in laser-etched silicon nanostructures

Department of Physics, Indian Institute of Technology Delhi, New Dilli, NCT, India
Journal of Applied Physics (Impact Factor: 2.18). 03/2007; 101(6):064315. DOI: 10.1063/1.2713367


Photoexcitation dependent Raman studies on the optical phonon mode in silicon nanostructures (Si NS) prepared by laser-induced etching are done here. The increase in the asymmetry of the Raman spectra on the increasing laser power density is attributed to Fano interference between discrete optical phonons and continuum of electronic excitations in the few nanometer size nanoparticles made by laser-induced etching. No such changes are observed for the same laser power density in the crystalline silicon sample or ion-implanted silicon sample followed by laser annealing. A broad photoluminescence spectrum from Si NS contains multiple peak behavior, which reveals the presence of continuum of electronic states in the Si NS. (c) 2007 American Institute of Physics.

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    • "Now to see the combined effect of F-C on Raman line shape the following equation has been taken which is already used by many authors in the literatures[14] [15] [3537]. "
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    ABSTRACT: Theoretical Raman line shape functions have been studied to take care of quantum confinement effect and Fano effect individually and jointly. The characteristics of various Raman line shapes have been studied in terms of the broadening and asymmetry of Raman line shapes. It is shown that the asymmetry in the Raman line-shape function caused by these two effects individually does not add linearly to give asymmetry of line-shape generated by considering the combined effect. This indicates existence of interplay between the two effects. The origin of interplay lies in the fact that Fano effect itself depends on quantum confinement effect and in turn provides an asymmetry. This can not be explained by considering the two effects contribution independent of each other.
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    • "means that the Si nanostructures are uniform and does not contain a range of sizes. In contrast, it is reported [39] that a double PL peak is observed from LIE samples due to two different dominant nanostructure sizes available in LIE samples. LIE samples contain different sized Si nanostructures because a Gaussian beam is used to prepare the sample using LIE. "
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    ABSTRACT: Porous silicon (p-Si), prepared by two routes (metal induced etching (MIE) and laser induced etching (LIE)) have been studied by comparing the observed surface morphologies using SEM. A uniformly distributed smaller (submicron sized) pores are formed when MIE technique is used because the pore formation is driven by uniformly distributed metal (silver in present case) nanoparticles, deposited prior to the porosification step. Whereas in p-Si, prepared by LIE technique, wider pores with some variation in pore size as compared to MIE technique is observed because a laser having gaussian profile of intensity is used for porosification. Uniformly distribute well-aligned Si nanowires are observed in samples prepared by MIE method as seen using cross-sectional SEM imaging. A single photoluminescence (PL) peak at 1.96 eV corresponding to red emission at room temperature is observed which reveals that the Si nanowires, present in p-Si prepared by MIE, show quantum confinement effect. The single PL peak confirms the presence of uniform sized nanowires in MIE samples. These vertically aligned Si nanowires can be used for field emission application.
    Silicon 03/2014; DOI:10.1007/s12633-014-9242-y · 1.07 Impact Factor
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    • "Raman spectra recorded using 0.2 kW/cm2 are fitted using phenomenological phonon confinement model [5,6] to calculate the most probable Si NSs size. Using these NSs sizes, Raman spectra recorded using 0.88 kW/cm2 are fitted using Fano-Raman line-shape [10] to find the Fano asymmetry parameter to see the effect of Si NSs size on the Fano interaction. Higher Fano interaction is seen for smaller Si NSs as compared to large Si NSs. "
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    ABSTRACT: Photo-excitation and size-dependent Raman scattering studies on the silicon (Si) nanostructures (NSs) prepared by laser-induced etching are presented here. Asymmetric and red-shifted Raman line-shapes are observed due to photo-excited Fano interaction in the quantum confined nanoparticles. The Fano interaction is observed between photo-excited electronic transitions and discrete phonons in Si NSs. Photo-excited Fano studies on different Si NSs show that the Fano interaction is high for smaller size of Si NSs. Higher Fano interaction for smaller Si NSs is attributed to the enhanced interference between photo-excited electronic Raman scattering and phonon Raman scattering.
    Nanoscale Research Letters 03/2008; 3(3-3):105-108. DOI:10.1007/s11671-008-9120-x · 2.78 Impact Factor
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