Space charge effects in field emission nanodevices

Abstract

Electron field emission from a single nanoemitter is a barrier tunneling, quantum mechanical process that can, therefore, be described by the well-known Fowler-Nordheim (FN) equation. At high emission current densities, however, the space charge caused by the cathode may affect the current density-voltage (J-V) characteristics predicted by the FN theory. In this study, we theoretically investigated the effect of space charge on FE nanodevices, including diode and triode structures. The J-V characteristics of FE nanodevices were obtained by analytically (diode structures) or numerically (triode structures) solving the coupled FN equation and Poisson's equation. We discuss the behavior of FE nanodiodes and nanotriodes displaying different geometries, dimensions and work functions of their emitter materials. In the high current density region, space charge plays an important role in FE nanodevices; the threshold current density of space-charge limitation is related to the electric field distributions. Besides, our theoretical results are in good agreement with the experimental results reported previously.

Novel borothermal route for the synthesis of lanthanum cerium hexaborides and their field emission properties

“…The mechanism of two-slope field enhancement behaviour of lanthanum-cerium hexaboride is not yet clear. However, for zinc oxide and CNT, the two-slope behaviour has been reported earlier and attributed to the space charge effect [20], surface adsorbate [21] and damage of emission site [22] at high voltage. The high enhancement factor (b) of La 0.5 Ce 0.5 B 6 may be attributed to the morphology (pyramidal-shaped with sharp tip (tip plays important role in enhancement)) as well as the composition of lanthanum cerium hexaboride.…”

“…9, Fig. S5a-c) of hexaborides show linear behavior which indicates that the emission from lanthanum-cerium hexaboride films follow the tunneling mechanism [20][21][22]. The local field near the emission site, F local is related to applied field, inter-electrode spacing (d) and field enhancement factor (b).…”

Effect of nitrogen and hydrogen on the growth of multiwall carbon nanotubes on flexible carbon cloth using thermal chemical vapor deposition

“…In addition, it is interesting to note that although the density of MWCNTs at 0 sccm of N 2 flow rate is larger than 2000 sccm of N 2 flow rate, the threshold field of MWCNTs at 2000 sccm is lower than 0 sccm. This lower threshold field is mainly due to the geometry enhancement (since the diameter of MWCNTs at 2000 sccm is smaller than the diameter at 0 sccm) [31]. Another evidence can be seen in the IeV characteristics of Fig.…”

The diode emission system with the spherical field emitter mathematical modeling

“…The interior of system's domain is contained with different dielectrics. The boundary-value problem for the Laplace's equation is solved in the spherical coordinates.Field electron emitter (FEE) as sphere on cone occur is used in vacuum electronic devices [1]. FEEs can be fabricated by coating a metallic or a carbon emitter with a layers of dielectric materials [2].…”

“…Field electron emitter (FEE) as sphere on cone occur is used in vacuum electronic devices [1]. FEEs can be fabricated by coating a metallic or a carbon emitter with a layers of dielectric materials [2].…”