Highly 28Si enriched silicon by localised focused ion beam implantation

• Published in: Communications materials 2024-05, Vol.5 (1), p.57-7, Article 57
• Main Authors: Acharya, Ravi, Coke, Maddison, Adshead, Mason, Li, Kexue, Achinuq, Barat, Cai, Rongsheng, Gholizadeh, A. Baset, Jacobs, Janet, Boland, Jessica L., Haigh, Sarah J., Moore, Katie L., Jamieson, David N., Curry, Richard J.
• Format: Article
• Language: English
• Subjects: 639/301/1005; 639/301/119/1000; Chemistry and Materials Science; Coherence; Crystallization; Enrichment; Ion beams; Ion implantation; Irradiation; Materials Science; Nuclear spin; Quantum computing; Qubits (quantum computing); Secondary ion mass spectrometry; Silicon; Silicon wafers; Solid phases
• ISSN: 2662-4443; 2662-4443
• DOI: 10.1038/s43246-024-00498-0

Solid-state spin qubits within silicon crystals at mK temperatures show great promise in the realisation of a fully scalable quantum computation platform. Qubit coherence times are limited in natural silicon owing to coupling to the 29 Si isotope which has a non-zero nuclear spin. This work presents a method for the depletion of 29 Si in localised volumes of natural silicon wafers by irradiation using a 45 keV 28 Si focused ion beam with fluences above 1 × 10 19  ions cm −2 . Nanoscale secondary ion mass spectrometry analysis of the irradiated volumes shows residual 29 Si concentration down to 2.3 ± 0.7 ppm and with residual C and O comparable to the background concentration in the unimplanted wafer. After annealing, transmission electron microscopy lattice images confirm the solid phase epitaxial re-crystallization of the as-implanted amorphous enriched volume extending over 200 nm in depth. Silicon spin qubits are promising for the realisation of scalable quantum computing platforms but their coherence times in natural silicon are limited by the non-zero nuclear spin of the 29 Si isotope. Here, enriched 28  Si down to 2.3 ppm residual 29 Si is obtained by focused ion beam implantation.