Effect of electrical conduction on the electron emission properties of diamond needles

Abstract

Single crystal diamond needles are promising structures as point electron sources. However, the low electrical conductivity of diamond limits their application as high brightness electron sources. Here we study experimentally and numerically the field emission behavior of single crystal diamond needles, in order to better explain the link between the low electrical conduction, the non-homogeneous field distribution in the needle, the evolution of the field enhancement factor and the saturation of the Fowler–Nordheim plot. Field emission current and voltage loss were measured as a function of the applied voltage. Numerical modelling was used to solve conduction, emission and Laplace equations taking into account the real geometry of the field emitter and its environment. The combination of experimental and numerical results shows that the conduction behavior and the field enhancement factor depend on the diamond geometry. Moreover, the Fowler–Nordheim plot saturation is shown to be affected by the electrostatic environment which can limit the range of voltage losses that can appear along the diamond needle and hence limit the field emission current. At the same time, the increase of the emission current at high field, which is sometimes argued to be caused by the breakdown of the field emitter, is here presented as a simple consequence of the conduction properties of the field emitter as it was already shown for silicon field emitters.

Keywords

• diamond
• field emission
• voltage loss
• Fowler–Nordheim
• Poole–Frenkel