Multi material rectifying device fibers

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2009.Cataloged from PDF version of thesis.Includes bibliographical references.Electronic and optoelectronic device processing is commonly thought to be incompatible with much simpler thermal drawing techniques used in optical fiber production. The incorporation of metals, polymer insulators, and chalcogenide semiconductors into structured fibers has reversed this paradigm and made it possible to realize optoelectronic device functionalities at fiber optic length scales and cost. In spite of the surprising robustness of this processing technique, the electronic performance and complexity of these optoelectronic fiber devices has been constrained by the small set of materials compatible with the fabrication method and the disordered nature of the semiconductor. Specifically, the high density of defects inherent to the amorphous chalcogenide semiconductors precludes the ability to create spatially extended internal electric fields necessary to create more sophisticated devices such as diodes and transistors. In this work, the design, fabrication, and characterization of the first fiber-integrated diode is described. The relevant optical, thermal, and electronic properties of candidate materials compatible with the thermal fiber drawing process are described and measured. Phase changing semiconductors are incorporated into the fiber having both amorphous properties amenable to thermal drawing and crystalline properties ideal for electronic devices. Combinations of metals and semiconductors that form both blocking and non-blocking contacts are identified and combined to form the first diode device that is compatible with the thermal drawing process. Techniques are developed to reduce the dimensions of the resulting devices by an order-of- magnitude compared to all previous multimaterial device fibers.(cont.) A series of measurements of both compositional and potential spatial variation are used to determine that compound formation at specific metal semiconductor interfaces control the rectifying behavior of the fiber integrated rectifying junction. This work demonstrates the ability to synthesize compounds during fiber drawing to create complex electronic structures and combine them to form basic building blocks of circuits into arbitrary long fiber, paving the way to increasingly complex electronic structures and truly intelligent fibers and fabrics.by Nicholas D. Orf.Ph.D