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

Abstract

Carbon nanotubes (CNTs) were synthesized by a DC thermal plasma method. Afteroptimizing the synthesis parameters such as the pressure, current etc, the synthesizedproducts, and the anodic deposit in particular, were characterized by scanning electron andtransmission electron microscopy. The morphology of the product was ascertained to bemultiwalled carbon nanotubes in a large ratio. The diameters of these nanotubes were ofthe order of 30–50 nm with lengths extending up to a micron and sometimes even 2 or3 µm.The field emission properties of these nanotubes were then studied. The CNTs were depositedon a metal stub which acted as the cathode. Care was taken to ensure complete coverage ofthe stub to remove any possibility of emission from the metallic stub itself. The emissionstudies were performed in a stainless steel chamber under a dynamic vacuum in the range of10−8 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 wascrucial in estimating accurately the emitting area and thus the field enhancement factor. TheI–V curves for the field emission were recorded for various distances between the electrodes. Theresults are shown here.