Isotopically enriched silicon (Si) can greatly enhance qubit coherence times by minimizing naturally occurring ${}^{29}\mathrm{Si}$ which has a nonzero nuclear spin. Ultrahigh fluence ${}^{28}\mathrm{Si}$ ion implantation of bulk natural Si substrates was recently demonstrated as an attractive technique to ultrahigh ${}^{28}\mathrm{Si}$ isotopic purity. In this work, we apply this ${}^{28}\mathrm{Si}$ enrichment process to produce ${}^{28}\mathrm{Si}$ and ${}^{28}\mathrm{Si}$-on-insulator (SOI) samples. Experimentally, we produced a ${}^{28}\mathrm{Si}$ sample on natural Si substrate with ${}^{29}\mathrm{Si}$ depleted to 7 ppm (limited by measurement noise floor) that is at least 100 nm thick. This is achieved with an ion energy that results in a sputter yield of less than one and an ultrahigh ion fluence, as supported by our improved computational model that is based on fitting a large number of experiments. Further, our model predicts the ${}^{29}\mathrm{Si}$ and ${}^{30}\mathrm{Si}$ depletion in our sample to be less than 1 ppm. In the case of SOI, ion implantation conditions are found to be more stringent than those of bulk natural Si in terms of minimizing threading dislocations upon subsequent solid phase epitaxy annealing. Finally, we do not observe open volume defects in our ${}^{28}\mathrm{SOI}$ and ${}^{28}\mathrm{Si}$ samples after SPE annealing ($620{}^{\circ }\mathrm{C}$, 10 min).

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• Crystal defects
• Quantum communication, protocols & technology
• Elemental semiconductors
• Materials analysis & modification by accelerators
• Ion implantation
• Isotope separation & enrichment
• Materials modeling
• Monte Carlo methods