Finite element modeling of the field enhancement phenomenon in nanoscale field emitters and field ionizers

Ramin Banan Sadeghian and Mojtaba Kahrizi,
Concordia University

Interest in nanoscale field emission and field ionization devices has been renewed in recent years. Several new materials and novel device concepts have been introduced with promising field emission (FE) and field ionization (FI) behavior. Among them vertical ZnO nanowires (ZnONW) exhibit unique FE properties at relatively low applied electric fields.

Using FEMLAB, we employed finite element simulations to demonstrate the field enhancement effect near the tip top of a single ZnONW within a FE/FI cell. A maximum linear field enhancement factor of ß = 3.8 was obtained for our model. It was also proposed that the presented finite element analysis be used to evaluate the field emission current induced by the local electric field, instead of linear scaling the applied field by ß in the Fowler–Nordheim equation. Moreover, it was shown that for the cell configured as a field ionizer (with the nanowire as anode), the electric energy density in the interelectrode gap increases 15 fold compared to that of a cell with flat electrodes.