Harnessing Control of Composition and Morphology in Semiconductor Nanowires: From Fundamentals to Function (J. Christesen)

Much of the research on semiconductor NWs has revolved around precisely tuning the optical and electrical properties of the NW through either changes in either composition or morphology, and in this presentation, we will explore the fundamental effects of these changes and how to utilize this knowledge to encode functionality in the NWs for various applications. A common structure that utilizes changes in composition is a p-n junction which is used for a diverse range of functions including sensors and solar cells. Despite being a ubiquitous device architecture, the physics of these nanoscale junctions has not been thoroughly evaluated. We, therefore, investigate p-n junctions both along the axial and radial directions of a Si NW through finite element modeling to identify and evaluate key parameters of NW photovoltaic performance, and its prospect as a technology for solar energy conversion. In order to further tune the properties of NWs beyond changes in composition, we develop a method to break the conventional “wire” symmetry and encode sub-10 nm morphological resolution in Si NWs via a process termed ENGRAVE (Encoded Nanowire GRowth and Appearance through VLS and Etching). We utilize the ENGRAVE process to not only encode new functionality in Si NWs for a variety of applications including solid state memory and surface enhanced Raman spectroscopy but also to study the fundamentals of the VLS mechanism.