Stress state of embedded Si nanocrystals

Monte Carlo simulations shed light on the stress state of Si nanocrystals embedded in amorphous silica, unraveling and explaining its nature and origins. This is achieved by generating detailed stress maps and by calculating the stress profile as a function of size and distance between the nanocrystals. For normal oxide matrix densities, the average stress in the nanocrystal core is found to be compressive, reaching values of 3-4 GPa, in excellent agreement with experimental measurements. It drastically declines at the interface, despite the existence of several highly strained geometries. Tensile conditions prevail in nanocrystals embedded in densified silica matrices. The nanocomposites are shown to be stable, at close interdot distances, against segregation and phase separation