Strong Raman yield enhancement in large Si nanocrystals from ultraviolet to infrared: Density and shape dependence

Abstract

Silicon nanocrystals, few hundred nanometers in size, demonstrate impressive Raman yield enhancement. We report, first, the enormous Raman yield enhancement obtained with octahedral‐shaped nanocrystals in a wide wavelength range going from the ultraviolet, through the visible, to the infrared. We observed, along with the main Si peak amplification at 521 cm−1, also the amplification of the 480 cm−1 broad peak of a thin amorphous Si layer embedded between the nanocrystals, together with an amplification of the overall background under both Raman peaks. In order to clarify the mechanism governing the previous enhancements, the previous data were completed exploring the influence of shape by using irregular nanocrystals of similar size. These latter nanocrystals showed an amplified Raman yield, although reduced with respect to those of octahedral shape. Collected data, displayed as a function of the size and density, have been interpreted and discussed.

Raman amplification for trapped radiation in crystalline single Si nanoparticle

“…A huge enhancement of the first-order Raman peak was recently reported for Si nanoparticles (Si-NP) 25 . These Si-NP also showed an enormous photoluminescence emission, with nonlinear thermal behaviour.…”

“…The principal fields of applications are the optical and electrical ones since they are strongly related to several devices. Giant photoluminescence emission 2,[23][24][25] , surface-enhanced stimulated emissions 26 , whispering-gallery sensors 27 , and carrier multiplication in photovoltaics 28 are of particular interest for the involved applications.…”

“…In these cases, the sample was made of agglomerated Si-NPs forming a porous layer up to a few microns in thickness. Two concurrent mechanisms were suggested to justify the large Raman peak amplification and the enhancement of radiative production 25,29 . The first was ascribed to the single-photon contribution whenever the radiation is trapped and scattered several times inside the Si-NP before absorption or escape.…”

On the Redox Activity of the Solid Electrolyte Interphase in the Reduction/Oxidation of Silicon Nanoparticles in Secondary Lithium Batteries

“…Si NPs were synthesized in the plasma through electron impact dissociation of SiH 4 and subsequent reactions. [58] After nucleation, the Si NPs were let to grow until the plasma was switched-off and fall on the substrate. [59,60] The process time was set to 45 s although such long time was not related to Si NPs nucleation, which was generally of few milliseconds, but it was needed to let them to grow in the plasma.…”

Recent advances in linear and nonlinear Raman spectroscopy. Part XIV

“…Their findings should be useful for further analysis of phonon properties and determination of thermal conductivity of supported TiS 2 thin films for advanced electronics devices. Faraci et al [ 95 ] explored strong Raman enhancement in large Si nanocrystals from the ultraviolet to the infrared using density and shape dependence. They found enormous Raman yield enhancement from octahedral‐shaped nanocrystals over this broad spectral range.…”