Study of field emission of multiwalled C nanotubes synthesized by arc discharge

Carbon nanotubes ( CNTs) were synthesized by a DC thermal plasma method. After optimizing the synthesis parameters such as the pressure, current etc, the synthesized products, and the anodic deposit in particular, were characterized by scanning electron and transmission electron microscopy. The morphology of the product was ascertained to be multiwalled carbon nanotubes in a large ratio. The diameters of these nanotubes were of the order of 30 - 50 nm with lengths extending up to a micron and sometimes even 2 or 3 mu m. The field emission properties of these nanotubes were then studied. The CNTs were deposited on a metal stub which acted as the cathode. Care was taken to ensure complete coverage of the stub to remove any possibility of emission from the metallic stub itself. The emission studies were performed in a stainless steel chamber under a dynamic vacuum in the range of 10(-8) Torr. The field emitted current was detected using a phosphorus coated indium tin oxide ( ITO) glass. The phosphorus coating also helped in imaging the tips of the nanotubes. This was crucial in estimating accurately the emitting area and thus the field enhancement factor. The I-V curves for the field emission were recorded for various distances between the electrodes. The results are shown here.