Universal field-emission model for carbon nanotubes on a metal tip

Electron-field-emission properties have been investigated systematically for carbon nanotubes (CNTs) fabricated on a metal tip. With a vacuum gap of 0.7 mm, the threshold field is as low as 0.7 V/mum and the current density approaches 10 mA/cm(2) at an electronic field of 1.0 V/mum. The emission current is quite stable with very low fluctuation. The emission behavior is in excellent agreement with Fowler-Nordheim theory and no current saturation is found even with an emission current reaching 1 A/cm(2). A universal relationship 1/beta=d(2)/d+1/beta(0) between the field amplification factor beta and the vacuum gap d is developed within a two-region field-emission model. This relationship provides the basis for a microscopic understanding of CNT emitters and is applicable to other systems as well. (C) 2002 American Institute of Physics.