Achieving a narrow size distribution of Au particles at a precise depth in SiO₂ by segregation of Au precipitates

We propose a new method of confining Au nanoparticles of a narrow size distribution at a precise depth in an SiO₂ matrix. The process involves the formation of nanocavities in silicon by hydrogen implantation and annealing (at 850 °C), followed by Au gettering to and precipitation in such cavities and a wet oxidation at 900 °C. Starting with a silicon-on-insulator wafer, Au precipitates can be segregated behind a growing Si/SiO₂ interface during wet oxidation and ultimately trapped in SiO₂ at the front interface of a buried oxide layer. The shape of the precipitates has been examined by transmission electron microscopy and found to be spherical. The average diameters of these precipitates before and after oxidation have been determined as around 15 nm and 30 nm, respectively.