Targeted enrichment of 28Si thin films for quantum computing
Ke Tang, Hyun S. Kim, Aruna N. Ramanayaka, David S. Simons, Joshua M. Pomeroy
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 % (0.832 × 10-6 mol/mol 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 for quantum computing remain unknown. Here we use hyperthermal energy ion beam deposition with silane gas to deposit epitaxial 28Si. We switch the mass selective magnetic field periodically to control the 29Si concentration. We develop a model to predict the residual 29Si isotope fraction based on deposition parameters and measure the deposited film using secondary ion mass spectrometry (SIMS). The measured 29Si concentrations show excellent agreement with the prediction, with an average accuracy of (90 ± 5.0) %.