High-Resolution Morphological Control of Silicon Nanowires for Bottom-Up Photonics and Plasmonics

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Technical Description: This project aims to develop a bottom-up method for high-resolution control of silicon nanowire morphology. Semiconductor nanowires have traditionally been limited to cylindrical, axially symmetric structures, yet many new technological applications for nanowires could be enabled with a method to break the axial symmetry and produce well-controlled shapes along the nanowire axis. In pursuit of this goal, this research project investigates fundamental aspects of in-situ chemical doping of silicon nanowires and doping-dependent wet-chemical etching processes. The research is expected to yield fundamental insights into the incorporation of dopants during both vapor-liquid-solid and vapor-solid-solid nanowire growth processes. By systematically exploring the dependence of wet-chemical etch rates on nanowire doping, this project is also expected to enable the synthesis of nanowires in which the axial morphology is modulated on length scales ranging from a few nanometers to several micrometers. The optical absorption and scattering characteristics of the morphologically-controlled nanowires are studied through a combination of experiment and finite-element simulations to determine their potential technological application in the areas of nanophotonics and plasmonics.Non-technical Description: Most well-developed semiconductor technologies require the patterning of materials on a microscopic scale. Semiconductor nanowires often lack the nanometer-scale patterning capability, which is necessary for many applications. This project aims to develop a simple chemical method to encode high-resolution patterns into nanowires composed of silicon. The results from this project are expected to substantially expand our fundamental understanding of nanowire growth processes. The optical properties of the wires are studied to determine their potential application for technologies that use light for information processing and computing applications. This project is integrated into educational and outreach activities involving middle-school through graduate-level students. Graduate and undergraduate students involved in the research on a year-round basis are trained in a cross-disciplinary environment that bridges concepts from chemistry, engineering, physics, and materials science. Through a summer outreach program, middle- and high-school students from traditionally underrepresented groups experience hands-on research emphasizing original concepts and discovery. The overall project is designed to foster collaboration between students with a diverse range of backgrounds using concepts and techniques derived from all areas of the physical sciences.