Small-angle neutron scattering measurement of silicon nanoparticle size

Abstract

We have determined the particle size distribution profiles of octane-terminated siliconnanoparticle suspensions, produced using the sonication of electrochemically etchedSi wafers. Small-angle neutron scattering data was analyzed separately in high(0.4 nm−1<q<3.0 nm−1) and low(q<0.4 nm−1) scattering vectorranges. Data in the high q range is consistent with the log-normal distribution of isolated spherical particles with median diameterd = 3 ± 0.2 nm.Particle sizes were also indirectly assessed from photoluminescenceand optical transmission spectroscopy using the size/bandgap relation:Eg = 3.44d−0.5, whereEg is ineV and d in nm. Both measurements were consistent with the particle size distribution profiles,estimated from ANS data fitting and TEM image analysis.A subpopulation of larger, irregular shape structures in the sizerange 10–50 nm was also indicated by neutron scattering in the lowq range and HRTEM images. However, further studies are warranted toexplain a relationship between the slope of scattering intensity versusscattering vector dependence in the intermediate scattering vector range(0.4 nm−1<q<1.0 nm−1) and the role of non-geometrical Si nanoparticle characteristics (mutual interaction forces,surface termination, etc).