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Title: Diamond sensors for extreme environments
Author: Parfitt, William
ISNI:       0000 0004 7970 6224
Awarding Body: UCL (University College London)
Current Institution: University College London (University of London)
Date of Award: 2019
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Diamond is unique in its collection of superlative mechanical, electronic and electrochemical properties. Through the investigations presented in this work these properties are brought to the foreground to demonstrate how previously intractable problems may be solved by the research and development of diamond-based sensors for extreme environments. One such solution is the use of diamond as an innovative component in robust, solid-state neutron detection. A comprehensive computational Monte Carlo model is built to simulate and optimise the efficiency and energy resolution of diamond neutron detector geometries, taking into account the significant influence of statistical charge carrier generation, trapping and recombination as well as electronic noise. Consequently, a new and promising route to highly efficient diamond neutron detectors is presented. Additionally, machine learning is used to help improve upon the Bethe equation and semi-empirical fitting methods for the calculation of low-energy ionic stopping powers. A regressive decision tree ensemble is shown to be capable of remarkably accurate predictions for any conceivable ion and target combination when compared to existing experimental data. The concurrent development of diamond water quality sensors is also described, paving the way for multi-functional monitoring of harsh fluids over extended periods of time. Boron-doped diamond layers are grown on polycrystalline intrinsic substrates and processed for characterisation. Electronic measurements, including circular transmission line and temperature-dependent impedance spectroscopy, are performed to determine key properties of the layers for use in high temperature applications. Finally, these devices are processed to form novel prototypes for sensors in harsh environments. Results are presented for a diamond pH sensor using an ionsensitive field effect transistor (ISFET) structure, and an amperometric dissolved oxygen (DO) sensor.
Supervisor: Richard, J. Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available