Controlled Single-ion Implantation for Charge and Spin-based Silicon Quantum Computer Devices

ARC Centre of Excellence for Quantum Computer Technology, Microanalytical Research Centre, School of Physics, University of Melbourne

3.30pm, Friday 3 September 2004, AR103 Seminar Room, Graduate Research Centre

Devices that employ single atoms to store and manipulate information will be constructed in the near future. For example, a solid state quantum computer device has been proposed that encodes information in the nuclear spin of shallow arrays of single 31P atoms (qubits) in a matrix of pure silicon. Construction of these devices presents formidable challenges. We have proposed a strategy that employs single ion implantation, with an energy of 10 to 20 keV, to load the qubits into prefabricated cells of the device that employs detector electrodes adjacent to the cells that can detect single keV ion strikes appropriate for the fabrication of shallow arrays. Our method utilises a pure silicon substrate with a very high resistivity, a thin (5 nm) silicon dioxide surface layer, biased electrodes applied to the surface and sensitive electronics that can detect the charge transient from single keV ion strikes. A key feature of these detectors is the ultra-thin surface dead layer. The charge collection efficiency of these detectors has been measured with MeV ions, keV x-rays and keV ions. We show that our detectors have a near 100% charge collection efficiency for MeV ions and keV x-rays. We show pulse height spectra from 15 keV H, He and P ion impacts allowing measurement of the pulse height defect for the keV ions. We review the role of these detectors in the construction of a two qubit device that will test many of the essential mechanisms of a revolutionary solid state quantum computer.

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