Conti, Pierandrea;
(2024)
Photoconductive microscopy of strained donor bound excitons in silicon.
Doctoral thesis (Ph.D), UCL (University College London).
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Abstract
The silicon donor spin has one of the longest coherence times among quantum systems and has shown great potential for quantum information and magnetic sensing applications. Among the research focus on the challenge of donor spin readout, the donor bound exciton (D0X) optical transition offers a promising hybrid optical-electrical spin readout method, spin-selectively ionising the donor via Auger decay. This work explores the miniaturisation of D0X photoconductive readout to the microscale in silicon devices. The electrical detection of ∼2000 shallow implanted phosphorus donors is achieved with a 2 µm focused laser beam within a pair of microfabricated metal-oxide planar contacts. High frequency D0X detection is further demonstrated by LC-resonant RF reflectometry, and it is employed to achieve microsecond pulsed D0X detection. Donor bound excitons are sensitive to lattice strain due to the strong silicon valence band spin-orbit coupling, yielding broadened, split peaks, a key factor in thermally strained microfabricated devices. The effect of strain on the D0X transition is first explored in an isotopically purified 28Si:P sample subject to calibrated uniaxial strain, detecting D0X induced spin polarisation by electron paramagnetic resonance. Strained bound excitons in micro-devices are then studied by means of laser scanning microscopy, showing good agreement with theoretical predictions by FEM solid mechanics simulations and highlighting the potential of donor bound excitons for micro-strain sensing. Finally, D0X induced donor spin polarisation is explored in microfabricated devices, with neodymium magnets and PCB antennas for magnetic field and microwaves generation. Electron spin polarisation is achieved under a continuous laser pump, and its sensitivity to experimental conditions is studied. Transient pump-probe and optical-microwave spin driving is explored, displaying a total absence of lasting donor spin polarisation and suggesting likely fast spin relaxation.
| Type: | Thesis (Doctoral) |
|---|---|
| Qualification: | Ph.D |
| Title: | Photoconductive microscopy of strained donor bound excitons in silicon |
| Open access status: | An open access version is available from UCL Discovery |
| Language: | English |
| Additional information: | Copyright © The Author 2024. Original content in this thesis is licensed under the terms of the Creative Commons Attribution-NonCommercial 4.0 International (CC BY-NC 4.0) Licence (https://creativecommons.org/licenses/by-nc/4.0/).Any third-party copyright material present remains the property of its respective owner(s) and is licensed under its existing terms. Access may initially be restricted at the author’s request. |
| UCL classification: | UCL UCL > Provost and Vice Provost Offices > UCL BEAMS UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences |
| URI: | https://discovery-pp.ucl.ac.uk/id/eprint/10197979 |
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