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QI: Fachverband Quanteninformation

QI 2: Implementations I

QI 2.9: Vortrag

Montag, 9. März 2026, 12:15–12:30, BEY/0245

Local isotopic enrichment of ²⁸Si for quantum applications — •Lukas Prager¹, Ewelina Gacka¹, Priyal Dadhich¹, Stefan Findeisen², Nico Klingner¹, and Gregor Hlawacek¹ — ¹Institute of Ion Beam Physics and Materials Research, Helmholtz-Zentrum Dresden-Rossendorf (HZDR), Bautzner Landstr. 400, 01328 Dresden, Germany — ²Department of Mechanical Engineering, HZDR, Bautzner Landstr. 400, 01328 Dresden, Germany

Donor spin qubits in silicon are a promising candidate in the search for a qubit that can be fabricated in a scalable way while exhibiting long coherence times. Achieving minimal decoherence requires a magnetic moment-free environment, called *spin vacuum*, which, in case of silicon, necessitates the suppression of the nuclear spin-bearing isotope ²⁹Si (4.7%). We perform this task by ²⁸Si focused ion beam (FIB) implantation with energies larger than 45 keV to implant more atoms than removing by sputtering. The usage of a FIB offers a time efficient and spatially resolved way to achieve the necessary fluences (>10¹⁹ ions/cm²), while the spatial confinement leaves the surrounding semiconductor materials and devices untouched. Our aim is to ultimately achieve remaining concentrations of ²⁹Si that are lower than centrifuge-based approaches (<10 ppm). The resulting spin vacuum areas are one of the fundamental building blocks of a scalable qubit platform based on bismuth donor spin qubits embedded into silicon. The bismuth atoms will be precisely implanted in a deterministic way. Besides that, our device will feature qubits coupled via mechanical modes and single electron transistor governed readout.

Keywords: Focused Ion Beam FIB; Donor spin qubits; Quantum Applications; Isotopic Enrichment