Recently, Smith et al. studied the effects of anode location in a modified scanning electron microscope [1]. The results show that as the separation of the carbon nanotube to anode increases, the threshold field decreases and the enhancement factor increases. Consistent results have been obtained in TEM measurements and theoretical calculations [2]. A tip-flat model has been proposed to explain this phenomenon. In Figure 1, an individual single-wall carbon nanotube (SWCNT) is grown vertically from the substrate (cathode), with a height L = 1μm and radius r=3.44 angstrom. In this paper, the field electron emission is simulated by a quantum/classical hybrid method [3,4] with the interest concentrated at separation of anode from the emitter.
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