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Title: Component development for an SOI integrated displacement sensor
Author: Ghisetti, Emanuele Alberto
ISNI:       0000 0004 9356 0233
Awarding Body: University of Glasgow
Current Institution: University of Glasgow
Date of Award: 2020
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The objective of this work was to design, model and develop a practical and compact optical system capable to measure the displacement a microelectromechanical system (MEMS) gravimeter. Integrating the optical readout will enable to achieve a resolution potentially down to 10 μgal per square root Hertz. This will allow a more compact measurement system that could revolutionize the way gravity surveys are performed. The different optical components required to create the displacement sensor have been studied, fabricated and characterised. The sensor is obtained by creating an integrated Michelson interferometer on an SOI chip. Each component has been optimised for the specific application starting from the optical or electrical simulations. The design phase has considered both the requirements for obtaining a compact system and the fabrication limitations and tolerances. To successfully create the required structures, the fabrication process required the development of tailored methods for the electron beam lithography and the etching, together with the improvement of the existing ones. The fabricated system demonstrated a resolution below 4 nm when measuring a moving mirror at 30 cm distance. The waveguide coupled Ge photodetector required for the integration has been extensively studied. A novel design showed and increased coupling efficiency between the silicon waveguide and the germanium structure. The charge sheet layer has also been modelled to give a better electric field profile distribution. The selective area growth of the germanium in silica trenches has been investigated with the purpose of reducing the number of defects present in the Ge detectors. This will reduce the sources of dark current and dark counts. All these improvements will enable to have small device footprints with low dark current and capacitance. A detector with high sensitivity will allow to have a high sensitivity on the displacement of the MEMS and in turn on the gravity measurements.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: TK Electrical engineering. Electronics Nuclear engineering