Negative resistance region in double-gated silicon field emission arrays

Double-gated silicon field emission arrays (FEAs) are fabricated with the tip 400 nm below the extraction gate and 600 nm below the focus. The diameters of the gate and focus apertures are 0.4 μm and 0.7 μm respectively. For this structure, an abrupt drop in anode current is observed when the focus voltage V_f is less than 12 V. For the range of focus voltages 4 V < V_f < 12 V, the anode current initially increases with the gate voltage because the net repulsive force is still small. The emitted current increases with V_G due to repulsion by the focus. Eventually, the anode current peaks and a negative resistance region ensue. Further increase of V_G shuts off the anode current. For focus voltage > 12 V, the balance between the emission and repulsive forces is such that there is a monotonic increase in anode current with V_G and shows no negative resistance region.