Implantation site design for large area diamond quantum device fabrication

With the number of qubits increasing with each new quantum processor design, it is to be expected that the area of the future quantum devices will become larger. As diamond is one of the promising materials for solid state quantum devices fabricated by ion implantation, we developed a single board diamond detector/preamplifier implantation system to serve as a testbed for implantation sites of different areas and geometry. We determined that for simple circular openings in a detector electrode, the uniformity of detection of the impinging ions increases as the area of the sites decreases. By altering the implantation site design and introducing lateral electric field, we were able to increase the area of the implantation site by an order of magnitude, without decreasing the detection uniformity. Successful detection of 140 keV copper ions that penetrate on average under 100 nm was demonstrated, over the 800 µm² area implantation site (large enough to accommodate over 2 × 10⁵ possible qubits), with 100% detection efficiency. The readout electronics of the implantation system were calibrated by a referent ²⁴¹Am gamma source, achieving an equivalent noise charge value of 48 electrons, at room temperature, less than 1% of the energy of impinging ions.