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

TL;DR

This study investigates charge distribution in crystalline and amorphous silicon nanoclusters within silica films using advanced spectroscopy techniques, revealing initial state effects dominate chemical shifts and electron screening varies with nanocrystal structure.

Contribution

The paper provides new insights into charge distribution and screening effects in silicon nanoclusters, distinguishing initial and final state contributions using XPS and TEM.

Findings

Chemical shift in nanocrystals is due to initial state effects.

Electron screening in nanocrystals is less effective than in bulk silicon.

Charge distribution differs between crystalline and amorphous nanoclusters.

Abstract

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.