Thesis presented November 10, 2017

Abstract:
Nanomaterials such as nanowires, nanoparticles and nanofibers have raised in past few years as a novel solution for next generation electronics thanks to their outstanding physical properties sustained by the capability of being integrated into microchips using conventional CMOS processes. Within the frame of this thematic, piezoelectric wires are one of subjects that has been studied the most recently. They have been used as an active material for electromechanical energy harvesting or sensing applications. This work studies GaN wire-based flexible piezoelectric sensors developed into two different architectures. We present a complete overview of the device fabrication and design starting from wire growth by MOVPE to the final electrical characterization of the sensors. Using Finite Element Modelling, we have explored the working principles of both architectures in order to understand deeply the potential generation mechanisms occurring at the wire level. This method was also used to help us establish the main de-sign rules which provided guideness for the fabrication: The effects of wire geometrical parameters and device dimensions on the electrical performances of the devices were studied from a theoretical point of view to figure out the optimal geometry to be targeted by the process and adapt it accordingly. Finally, electrical characterization has been carried out on several devices in order to approve the design rules experimentally. An appropriate automated mechanical bench has been used and a proper readout circuit was developed to be able to correctly detect the actual piezoelectric signal provided by the sensors.

Keywords:
Transducer, nanowires, GaN, Piezoelectrics, Modelling, Growth

On-line thesis.