Abstract
The field emission properties of the multi-walled carbon nanotubes (MWNT) with different length were studied. The results exhibit that the emission properties of these carbon nanotube films are intensively dependent on the length of carbon nanotubes and density of the film. The morphology of the different length MWNT films was investigated by scanning electron micrograph (SEM) and X-ray diffraction (XRD). Large differences of field emission characteristics among these MWNTs are observed, and explained in terms of a variation of the field enhancement factor. The longest MWNT exhibits the best field emission characteristics among all of the MWNTs studied. As a consequence, the field emission characteristics can be optimized by controlled the physical parameter of MWNT such as the tip density and the nanotube length, and the density of its film.