Growth of carbon nanotubes by thermal and plasma chemical vapour deposition processes and applications in microscopy

Single-walled carbon nanotubes (SWNTs) are grown from a methane feedstock by thermal chemical vapour deposition (CVD). An ethylene-hydrogen plasma generated in an inductively coupled plasma reactor primarily yields multi-walled carbon nanotubes and thicker fibres. In both cases, an iron catalyst layer and an aluminium underlayer are deposited by ion beam sputtering onto silicon wafers for the growth of carbon nanotubes (CNTs). The plasma process provides well-aligned multi-walled nanofibres useful for fabrication of electrodes and sensors and further tip functionalization whereas thermal CVD produces a mat of SWNT ropes. In addition, CNTs grown at the tips of silicon cantilevers are demonstrated to be ideal for high-resolution imaging of biological samples and simulated Mars dust grains using atomic force microscopy.