Effect of germanium concentration and oxide diffusion barrier on the formation anddistribution 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-sputteredGe–SiO2 films. The influence of a silicon oxide diffusion barrier inserted between theco-sputtered film and the substrate on the formation of the Ge nanocrystals isalso examined. We found that the effect of Si reduction on the Ge oxides playsan important role in the synthesis of Ge nanocrystals in co-sputtered Ge plusSiO2 samples with high Ge oxide concentration (80%) relative to the elemental Ge concentration(20%). The oxide diffusion barrier influenced the distribution of the nanocrystals bypreventing Ge from diffusing into the substrate such that nanocrystals were formedthroughout the film. When the Ge concentration was much higher (75%) than the Geoxide concentration, the contribution from the effect of Si reduction on the Geoxides in the formation of the nanocrystals is not significant. Again, the oxidediffusion barrier was very effective in preventing Ge atoms from diffusing into the Sisubstrate, and significant coarsening of the nanoclusters was observed in thesesamples.