Targeted enrichment of ²⁸Si for quantum computing

We report on the growth of isotopically enriched ²⁸Si epitaxial films with precisely controlled enrichment levels, ranging from natural abundance ratio of 92.2% all the way to 99.99987% (0.832ppm ²⁹Si). Isotopically enriched ²⁸Si is regarded as an ideal host material for semiconducting quantum computing due to the lack of ²⁹Si nuclear spins. However, the detailed mechanisms for quantum decoherence and the exact level of enrichment needed remain unknown. Here we use hyperthermal energy ion beam deposition with silane gas to deposit epitaxial ²⁸Si. In the meantime, we switch the mass selective magnetic field periodically to control the ²⁹Si concentration. A model predicting the residual ²⁹Si isotope fraction and the corresponding secondary ion mass spectrometry (SIMS) analysis are presented. Cross-sectional SEM/TEM will also been shown for the deposited ²⁸Si film throughout the range of enrichments.