High-Resolution Laser Diagnostics and Modeling of Single-Walled Carbon Nanotube Synthesis by Plasma-Enhanced CVD

Purdue University, West Lafayette IN

Investigators

Abstract

CBET-0828165 Lucht This research aims to develop key science for developing controlled synthesis of single-wall carbon nanotubes (SWCNTs) by plasma-enhanced chemical vapor deposition (PECVD). Carbon nanotubes have been shown to produce a wide range of outstanding physical properties with important technical and societal implications. However, some crucial properties depend strongly on material parameters that, to date, have been largely uncontrollable in the synthesis process. Well controlled fabrication of carbon nanotubes could enable breakthroughs across a vast range of applications, including ultrafast field-effect transistors and nanoelectronic circuits, direct energy-conversion processes, field-emission devices, high-temperature superconductors, textile fibers, and high-thermal-conductivity films. In addition, the microwave plasma has potentially very high concentrations of species such as CH3 and C-atom. These species are very important in combustion chemistry, but diagnostic techniques for these species are not well developed. The H2/CH4 plasma is thus of great interest as a testbed for the development of new optical diagnostic techniques. A technique pioneered by the research team aids synthesis by reducing concentration of atomic hydrogen from the growth surface, where they etch SWCNTs even at room temperature. The key is applying a positive electrical bias to the growth surface to repel H+ ions from it. Although the role of atomic H appears to be critical in these new processes, very little is known about the composition of the plasma near the growth surface. Spatially resolved optical measurements and complementary models, to be applied and developed in this work, are critical to understanding the role of species such as atomic H and carbon-containing precursors to CNT synthesis. The knowledge gained in this work is expected to enable the creation of synthesis protocols and models that in turn will aid the longer-term goal of controlled synthesis of CNT materials, structures, and devices. The proposed program will expose mechanical engineering graduate students to additional areas of science and engineering, such as molecular electronics and plasma physics, through existing collaborations with electrical engineers, material scientists, physicists, and chemists. In addition, exciting new research on nanotechnology and laser diagnostics will strongly attract domestic students into science and technology research careers through participation in Purdue's Summer Undergraduate Research Fellowship (SURF) program.