Direct-current plasma-enhanced chemical vapor deposition (CVD) with mixtures of acetylene and ammonia was optimized to synthesize aligned carbon nanotubes (CNTs) on Co- or Ni-covered W wires with regard to wire temperature, wire diameter, gas pressure, and sample bias. A phase diagram of CNT growth was established experimentally in this optimization process. It was revealed by transmission electron microscopy that Co-catalyzed CNTs encapsulated a

Field emitters comprised of aligned carbon nanotubes are shown to be promising as a primary electron source in an x-ray tube working in a non ultrahigh vacuum ambience. At a pressure of 2107 Torr, the nanotube emitters continue to emit electrons for more than 1h, and yield better resolved x-ray images than do thermionic emitters, independently of whether the sample is biological or non biological. The near-uniformity in energy distribution of electrons

A theoretical framework for the electron field emission from carbon nanotubes (CNTs)is discussed. Using the tunneling theory, the influence of the detailed electron energy dispersion is proven to be oflittle importance for the electron field emission. By means ofnumerical computations in a simplified model, the influence of the environment on the local field on a CNT is discussed for an aligned CNT film. In a simple triangular model for the

Using a tunneling approach for the field emission from a single carbon nanotube, expressions for the emission current as a function of the anode voltage and of the emitted electron energy spectrum are obtained. The low dimensionality of the electronic system of a carbon nanotube is taken into account. The extraction field on the nanotube’s tip is evaluated using numerical computations. For nanotubes of practical interest, having large enough diameters,