Spruce, Kieran J.;
(2025)
Fabrication of Novel Atomic-Scale Electronic Devices from Dopants in Silicon.
Doctoral thesis (Ph.D), UCL (University College London).
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Abstract
This thesis explores the development, fabrication, and characterisation of silicon based quantum devices using phosphorus and arsenic dopants. Utilising advanced techniques such as scanning tunnelling microscopy hydrogen desorption lithography, the research demonstrates precise atomic-scale control over dopant placement, essential for the creation of quantum dot single-electron transistors. Initially, the thesis focuses on phosphorus-doped silicon devices, replicating and enhancing methods from the National Institute of Standards and Technology (NIST). The successful fabrication of these devices, coupled with detailed studies of the fabrication processes of low-temperature epitaxy and rapid thermal annealing, reveals key insights into the optimisation of doping profiles and device performance. The introduction of a locking layer during fabrication was found to significantly improve the stability of phosphorus-doped devices, contributing to clearer observation of Coulomb blockade in electrical transport measurements. The research then shifts to arsenic as an alternative dopant, presenting the first scanning tunnelling microscopy defined arsenic-doped device and dual-species (P:As) nanoscale devices. Arsenic’s larger atomic radius and higher ionisation energy offer potential advantages for quantum devices, such as enhanced qubit stability and error correction capabilities. An iterative dosing scheme, involving predosing with phosphine, was developed to dramatically decrease the amount of unwanted arsenic dopant incorporation without introducing phosphorus dopants. Additionally, a novel three-way single electron transistor design was conceived and demonstrated, facilitating multi-terminal quantum measurements, enabling the study of quantum interference and multi-terminal transport effects. This device offers new methodologies for scaling quantum circuits. In summary, this thesis advances the field of dopant devices in silicon by showing our capability to use arsenic as a dopant, allowing for improvement in the ability to incorporate single dopant atoms at selected sites.
| Type: | Thesis (Doctoral) |
|---|---|
| Qualification: | Ph.D |
| Title: | Fabrication of Novel Atomic-Scale Electronic Devices from Dopants in Silicon |
| Open access status: | An open access version is available from UCL Discovery |
| Language: | English |
| Additional information: | Copyright © The Author 2025. 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. |
| Keywords: | quantum, dopant, silicon, STM, HDL, nanoscale |
| UCL classification: | UCL UCL > Provost and Vice Provost Offices > UCL BEAMS UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Engineering Science > Dept of Electronic and Electrical Eng |
| URI: | https://discovery.ucl.ac.uk/id/eprint/10203382 |
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