Effect of germanium concentration and oxide diffusion barrier on the formation and distribution of germanium nanocrystals in silicon oxide matrix

Abstract

The growth and formation of Ge nanocrystals embedded into a silicon oxide (SiO2) system synthesized by furnace annealing have been studied based on the Ge content of co-sputtered Ge–SiO2 films. The influence of a silicon oxide diffusion barrier inserted between the co-sputtered film and the substrate on the formation of the Ge nanocrystals is also examined. We found that the effect of Si reduction on the Ge oxides plays an important role in the synthesis of Ge nanocrystals in co-sputtered Ge plus SiO2 samples with high Ge oxide concentration (80%) relative to the elemental Ge concentration (20%). The oxide diffusion barrier influenced the distribution of the nanocrystals by preventing Ge from diffusing into the substrate such that nanocrystals were formed throughout the film. When the Ge concentration was much higher (75%) than the Ge oxide concentration, the contribution from the effect of Si reduction on the Ge oxides in the formation of the nanocrystals is not significant. Again, the oxide diffusion barrier was very effective in preventing Ge atoms from diffusing into the Si substrate, and significant coarsening of the nanoclusters was observed in these samples.