Chemical Engineering Seminar
Silicon is ubiquitous in modern semiconductor manufacturing. Well-established procedures for epitaxy, doping, etching, passivation, and contacting, perfected over more than five decades of use, enable a diverse array of electronic and photonic devices. Yet, the properties of bulk diamond cubic Si are fixed and ultimately limit its long-term usefulness. This talk will provide an overview of my group's recent efforts to reimagine the structure and properties of Si at the nanoscale. We accomplish this task via nanowire engineering in general, and more specifically, by exploiting the unique synthetic capabilities of the vapor-liquid-solid (VLS) growth technique. Our experimental approach couples the real-time in-situ infrared spectroscopic interrogation of nanowire chemistry with post-growth structure and property characterization. By identifying the specific chemical bonds present during synthesis, we provide a robust foundation from which to rationally achieve novel materials. The role of surface chemistry as the root cause of well known, yet previously unexplained, semiconductor nanowire growth phenomena will be discussed in detail. We subsequently leverage this fundamental knowledge to control the bilayer stacking of Si atoms and enable thermodynamically metastable superstructures with user-programmable periodicity. The ability to incorporate impurity atoms at concentrations well beyond their bulk solubility limit also permits the generation and tuning of mid-infrared localized surface plasmon resonances, which greatly enhances the ability of Si to interact with electromagnetic radiation.