Role of Plasma in Plasma Enhanced Chemical Vapour Deposition of Nanostructure Growth

摘要

Chemical vapour deposition (CVD) has become the preferred process for high yield growth of carbon nanotubes and nanofibres because of its ability to pattern growth through lithographic positioning of transition metal catalysts on substrates. Many potential applications of nanotubes such as field emitters require not only patterned growth but also vertical alignment. Some degree of alignment in thermal CVD processes can be obtained when carbon nanotubes are grown closely together as a result of van der Waals interactions. The alignment however is marginal, and the van der Waals prerequisite makes growth of freestanding nanofibres with thermal CVD unrealizable. The application of electric fields as a means of alignment has been shown to overcome this limitation, and highly aligned nanostructures can be grown if electric fields on the order of 0.5 V/micron are employed. Plasma enhanced CVD in various configurations including dc, rf, microwave, inductive and electron cyclotron resonance has been pursued as a means of enabling alignment in the CVD process.