The introduction of an ambient-temperature route for integrating high performance materials on flexible plastic substrates could enable exciting avenues in fundamental research, and innovative electronic and medical devices. However, the temperature constraints imposed by these substrates restrict the use of high carrier mobility materials, such as polycrystalline silicon, generally limiting these devices to the modest computational capabilities of amorphous silicon and organic semiconductor thin film transistors. The development of new materials and novel materials processes for overcoming this restriction could impact a broad spectrum of applications.
Semiconductor nanowires represent unique, high performance building blocks for electronic, photonic, and sensing devices. In this talk, I will present my work demonstrating that single-crystal nanowires can be hierarchically assembled onto flexible plastic substrates under ambient conditions to create multi component, fully integrated devices, including field-effect transistors, light-emitting diodes, ring oscillators, and electronic noses. These devices all exhibit performance metrics which meet or exceed the state-of-the-art for flexible electronics.
The key to our approach is the separation of the high-temperature synthesis of single-crystal nanowires from room temperature assembly, thus enabling fabrication of high-performance devices on virtually any substrate. Silicon nanowire field-effect transistors on plastic substrates display mobilities ivaling those of single-crystal silicon and exceeding those of amorphous silicon and organic transistors currently used for plastic electronics. Furthermore, we show that these systems can be integrated into ring oscillators on plastic which generate frequencies approaching the microwave, the highest observed frequencies for circuits based on nanoscale materials.
Finally, we exploit SiO2 surface chemistries to construct a “nano-electronic nose” library, which can distinguish acetone and hexane vapours via distributed responses. We also demonstrate that amide coupling of theoretically tailored peptide sequences to the arrays allows for selective discrimination of chemicals often found in the breath of sick patients. This excellent sensing performance coupled with biocompatible plastic could open up far-reaching opportunities in mobile computing, lightweight display, or even implantable monitoring applications.
