Structure and morphology controlled synthesis of nanocarbon materials and extremely narrow silicon nanowires

Nanotechnologies based on sp2 nanocarbon and silicon materials are developing very rapidly because of their unique mechanical, electronic, thermal and optical properties. However, large-scale synthesis of these 1-2D nanomaterials with desired structures still have many challenges due to the difficulty in controlling atomic-scale physical and chemical reactions during the synthesis process and a lack of understanding the underlying mechanism. The focus in our group is on investigating the synthesis processes for structure and morphology controlled CNTs, graphene, and nanoporous graphites using various chemical vapor deposition processes and nano-template synthesis method for applications in high density and multifunctional energy storage systems, flexible field-emission devices, superhydrophobic surfaces, friction and adhesion controlled lightweight materials. We also study and develop a technique to synthesize high density ultra-small SiNWs forming directly on Si wafers by investigating dry etching processes which can fully harness the unique chemical and quantum mechanical properties of silicon.


Nanomanufacturing processes for high performance and multifunctional sensors and energy storage devices

Scalable fabrication of nano, micro to macroscopic functional devices and systems that harness 2-3 dimensional and multiscale architectures of CNTs, graphene, and other 1-2D nanomaterials allow high performance, unique and multifunctional devices in broad ranges of applications. Our group studies nanomanufacturing processes such as fluidic & template guided assembly, direct printing transfer and device integration techniques for fabricating 1-3D dimensional nano/micro architectures of CNTs, graphene, 2D crystals and nanoporous film on various substrates (Si, SiO2, metals, polymer, and nano/micro-patterned flexible polymer surfaces). Using these unprecedented nanostructured architectures our group also studies and develops high performance photo-detector, ions and chemical sensors, flexible electrical interconnects, and flexible and transparent energy storage devices.


Solid-state re-engineering of sp2 nanocarbon networks

The combination of superior electronic, thermal, and mechanical properties makes nanocarbon (nanotube and graphene) networks an ideal building block for high-performance multifunctional materials, but these advantages are eroded in van der Waals connected networks. Our group investigates a novel carbon nanostructure engineering process by applying controlled input voltages in nanocarbon networks and fibers. This highly controllable method allows us to create covalently bonded carbon-carbon sp2 molecular junctions between assembled nanocarbon structures and can further transform them into various sp2 allotropes such as larger diameter SWCNTs, multi-walled carbon nanotubes, or multi-layered graphene nanoribbon with a tremendous property improvement. These molecular structure engineered nanocarbon (nanotube and graphene) networks and fibers are anticipated to be used in broader applications, particularly strong and highly conductive multifunctional fibers and reinforcements for lightweight and high performance composites, electronics, and electrodes for energy storage devices.