Semiconductor-based device architectures in multimaterial fibers

Semiconductor materials have given rise to today's digital technology and consumer electronics. Widespread adoption is closely linked to the ability to process and integrate them in devices at scale. Where flexibility and large surfaces are required, such as in smart textiles and distributed sensing, multifunctional fibers have a key role to play. However, to extend the realm of accessible semiconductor architectures by thermal drawing, in-depth understanding of the phenomena at play during heating and scaling down is required.Chapter 1 presents the challenges related to the processing and miniaturization of thin chalcogenide glass films and wires, namely capillary break-up and glass microstructure. By reaching micro- and nanoscale dimensions, photodetection sensitivity and response time can be improved by orders of magnitude. In Chapter 2, we report a scalable process to generate encapsulated flexible NW arrays with high aspect ratios and excellent tunable size and periodicity. Our strategy is to control nanowire self-assembly via the filamentation of a textured thin film under anisotropic stretching. This is achieved by coupling soft lithography, glancing angle deposition, and thermal drawing to obtain well-ordered meters-long nanowires with diameters down to 50 nm. We demonstrate that the nanowire diameter and period of the array can be decoupled and manipulated independently. We propose a filamentation criterion and perform numerical simulations implementing destabilizing long-range Van der Waals interactions. Applied to high-index chalcogenide glasses, we show that this decoupling allows for tuning diffraction. In Chapter 3 we extend this work by harnessing Mie resonances and demonstrate the possibility to fabricate macroscopic meta-grating superstructures for nanophotonic applications. Lithographic processes are used on a fiber preform to benefit from both the resolution offered by clean room tools and the scaling inherent to thermal drawing. A 1D metalens design is simulated and constructed. Fabrication constraints are accounted for, which feeds back into optimizing the focusing efficiency. An application to microfluidic index sensing is proposed.Next, we consider optoelectric architectures. In Chapter 4, we show contacting schemes for these fiber semiconducting architectures. This requires engineering of the rheological properties of the electrodes. Nanocomposites based on carbon nanoparticle fillers in a polymer matrix have the potential to fill this role, despite a trade-off in viscous and conducting properties, also impacting the transparency at small film thickness. An architecture preventing short circuits is proposed. Based on our understanding of their piezoresistive and capacitive behaviour, an application to in situ monitoring of the fabrication of resin composites is showed. As the fiber sensor remains embedded in the fabricated part, decoupled temperature and strain sensing is demonstrated. In Chapter 5, we discuss the scalable integration of a semiconductor junction, necessary for photovoltaics and sensitive photodetection. A ZnSe/Se heterojunction is characterized and an architecture for high geometric control is obtained based on solid Zn co-feeding. Combined to the presented highly viscous semi-transparent nanocomposites, all building blocks are lined up for the realization of an fiber planar photodiode.