(Invited) Designing Symmetric and Asymmetric Morphology in Silicon Nanowires to Encode Advanced Electronic and Photonic Functionality

Monday, 2 October 2017: 10:20
Chesapeake E (Gaylord National Resort and Convention Center)
J. F. Cahoon (University of North Carolina at Chapel Hill)
Silicon nanowires have been widely pursued as a technology for electronic, photonic, and renewable energy devices. Nevertheless, the implementation of nanowire technology has been limited by the extent to which the composition and morphology of wires can be controlled during synthesis. Here, we describe a bottom-up method—termed ENGRAVE (Encoded Nanowire GRowth and Appearance using VLS and Etching)—to modulate nanowire shape along the growth axis with sub-10 nanometer spatial resolution. Rapid modulation of phosphorus or boron incorporation during vapor-liquid-solid (VLS) growth encodes a high-resolution pattern of dopants in the wires. Subsequent solution processing is then used to selectively etch the wires, creating high resolution structures such as bow-ties, gratings, sawtooths, fractals, nanorods, sinusoids, and nanogaps. The capability to encode arbitrary morphology opens the door to new properties and functionality in the wires. For instance, we demonstrate how symmetric and periodic morphology can be used to design tunable photonic modes, enabling the coupling and waveguiding of light. In addition, we show how emergent electronic properties can be encoded through asymmetric morphology. The results highlight the broad set of new technologies that can be enabled through the design of precise sub-10 nanometer morphology in silicon nanowires.