The objective of this project is to establish the scientific and engineering foundation for the scalable manufacturing of semiconductor nanowires on flexible substrates via roll-to-roll processes. The strong demand for manufacturable nanowire technologies derives from the gap between the expectations generated by rapid advances in nanowire prototype devices (e.g., Si nanowire anodes in high-capacity Li-ion batteries) and the lack of fabrication methods at commercially relevant scales. The innovative roll-to-roll fabrication methods employed in the proposed project have significant potential to resolve road-blocks impending further progress towards emerging nanotechnologies.
Fundamentally, the growth of nanowires (NWs) from catalytic metal surfaces presents an interesting research challenge by virtue of the interplay of reaction kinetics and transport phenomena. Building on the shoulders of earlier studies of whisker growth via chemical vapor deposition, the surge of interest in nanostructured materials has led to remarkable advances in our understanding of fundamental kinetic and thermodynamics aspects of this important reaction. Recent reports of Si and Ge NW growth on bulk metal surfaces have revealed important departures from the well-established vapor-liquid-solid growth mechanism. These findings have created new opportunities for potentially transformative advances in NW processing and reaction engineering. Yet, many important fundamental aspects concerning the basic mechanism governing the growth have yet to be established.
We see the direct growth of nanowires on metal foils as exciting opportunity to answer basic scientific questions concerning nanowire fabrication and to apply that knowledge towards the development of continuous roll-to-roll methods.
Si nanowires present one of the most attractive electrode materials for high-capacity lithium ion batteries. The high charge capacity of a lithiated Si anode exceeds that of conventional graphite electrodes by almost tenfold, this property has been exploited to fabricate Si NW anodes for next-generation nanostructures lithium ion batteries. We are working with the energy materials center at Cornell (emc2) to investigate fundamental relationship between the nanowire structure, surface chemistry, and electrochemical performance in battery test cells.