Stress Evolution during Ge Nanoparticles Growth in a SiO₂ Matrix.

Area of Science:

• Materials Science
• Nanotechnology
• Solid State Physics

Background:

• Superlattices composed of alternating SiO2 and Ge layers are fabricated using multilayer magnetron deposition.
• These structures are then subjected to annealing in a nitrogen atmosphere at temperatures ranging from 500-750 °C.

Purpose of the Study:

• To investigate the structural and optical evolution of SiO2:Ge superlattices during annealing.
• To study the formation, growth, crystallization, and dissolution of germanium nanoparticles (nps).

Main Methods:

• Simultaneous grazing-incidence small- and wide-angle X-ray scattering (GISAXS/GIWAXS).
• Transmission electron microscopy (TEM).
• (Time-resolved) photoluminescence (PL) spectroscopy.

Main Results:

• In as-deposited films, small Ge clusters were already aggregated and laterally correlated.
• Ge nanoparticles began forming at annealing temperatures of 550 °C, remaining partially amorphous before crystallizing around 600 °C.
• At higher temperatures, Ge nanoparticles dissolved, leading to void formation in the SiO2 matrix.

Conclusions:

• The annealing process dictates the phase and morphology of Ge nanoparticles within the SiO2 matrix.
• Observed photoluminescence is attributed to defects at the Ge nanoparticle/SiO2 interface, persisting even after nanoparticle dissolution.