Small-angle neutron scattering measurement of silicon nanoparticle size

We have determined the particle size distribution profiles of octane-terminated silicon nanoparticle suspensions, produced using the sonication of electrochemically etched Si 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 vector ranges. Data in the high q range is consistent with the log-normal distribution of isolated spherical particles with median diameter d = 3 ± 0.2 nm. Particle sizes were also indirectly assessed from photoluminescence and optical transmission spectroscopy using the size/bandgap relation: E(g) = 3.44d(-0.5), where E(g) is in eV 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 size range 10-50 nm was also indicated by neutron scattering in the low q range and HRTEM images. However, further studies are warranted to explain a relationship between the slope of scattering intensity versus scattering 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).