Synthesized Silicon Nanostructures for Optical Switches and THz Electronics

Silicon nanowires have been widely pursued as a technology for electronic, photonic, and renewable energy devices. We developed a bottom-up method-termed ENGRAVE (Encoded Nanowire GRowth and Appearance using VLS and Etching)-to modulate nanowire shape and composition along the growth axis with sub-10 nanometer spatial resolution. Under precisely controlled synthetic conditions, the rapid modulation of phosphorus or boron incorporation during vapor-liquid-solid (VLS) growth can be used to encode a complex pattern of dopants in the wires. Subsequent solution processing can then be used to selectively etch the wires, creating high-resolution structures such as bow-ties, gratings, sawtooths, fractals, nanorods, sinusoids, and nanogaps. Several examples of the complex morphology in degenerately-doped p-type and n-type silicon are shown in Figure 1A and 1B, respectively.