Growth Mechanism and Surface Structure of Ge Nanocrystals Prepared by Thermal Annealing of Cosputtered GeSiO Ternary Precursor

Abstract EN

Ge nanocrystals (Ge-ncs) embedded in a SiO2 superlattice structure were prepared by magnetron cosputtering and postdeposition annealing.

The formation of spherical nanocrystals was confirmed by transmission electron microscopy and their growth process was studied by a combination of spectroscopic techniques.

The crystallinity volume fraction of Ge component was found to increase with crystallite size, but its overall low values indicated a coexistence of crystalline and noncrystalline phases.

A reduction of Ge-O species was observed in the superlattice during thermal annealing, accompanied by a transition from oxygen-deficient silicon oxide to silicon dioxide.

A growth mechanism involving phase separation of Ge suboxides (GeO x) was then proposed to explain these findings and supplement the existing growth models for Ge-ncs in SiO2 films.

Further analysis of the bonding structure of Ge atoms suggested that Ge-ncs are likely to have a core-shell structure with an amorphous-like surface layer, which is composed of GeSiO ternary complex.

The surface layer thickness was extracted to be a few angstroms and equivalent to several atomic layer thicknesses.