A study of the formation of isotopically pure 28Si layers for quantum computers using conventional ion implantation

We have investigated the use of conventional ion implantation to fabricate enriched Si-28 layers for use in quantum computers. The final compositions of samples enriched using ultra-low energy (ULE) (800 eV and 2 keV) and low energy (20 keV) Si-28 implants of varying fluences (1 x 10(16)-3.8 x 10(17) cm(-2)) using two different implanters were measured using channelled Rutherford Backscattering Spectroscopy (RBS). The dynamic, binary collision approximation program TRIDYN was used to model the implantation profiles to guide the analysis of the RBS spectra. It was found that ULE implants achieved high Si-28 enrichment levels but were heavily contaminated with oxygen due to poor vacuum in the implanter wafer end station. It was shown that oxidation could be reduced by using an accelerator with an end station with better vacuum and increasing the implant energy to 20 keV. However, TRIDYN simulations predict that the best Si-28 enrichment levels that could be achieved under these conditions would saturate at similar to 99.2% due to self-sputtering. We modelled a range of conditions with TRIDYN and so recommend low energies (<3 keV), ultra-high vacuum implantation for high Si-28 enrichment (>99.9%) with the lowest possible fluences (similar to 5-10 x 10(17) cm(-2)).

Automated summary

The study explored the use of conventional ion implantation to create enriched Si-28 layers for quantum computers. Results showed that low energy, ultra-high vacuum implantation is crucial for achieving high Si-28 enrichment levels exceeding 99.9%. However, utilizing ultra-low energy implants may lead to excessive oxygen contamination and compromise the enrichment efficiency.