An experimental study of charge distribution in crystalline and amorphous Si nanoclusters in thin silica films

Crystalline and amorphous nanoparticles of silicon in thin silica layers were examined by transmission electron microscopy (TEM), electron energy loss spectroscopy (EELS) and x-ray photoelectron spectroscopy (XPS). We used XPS data in the form of the Auger parameter to separate initial and final state contributions to the Si$_{2p}$ energy shift. The electrostatic charging and electron screening issues as well as initial state effects were also addressed. We show that the chemical shift in the nanocrystals is determined by initial state rather than final state effects, and that the electron screening of silicon core holes in nanocrystals dispersed in SiO$_2$ is inferior to that in pure bulk Si.