Volcano-structured double-gated field emitter arrays (VDG-FEAs) with different focusing electrode height have been fabricated and the focusing characteristics for each VDG-FEAs were evaluated in detail. The authors experimentally proved that lowering the focusing electrode was very effective to keep a high emission current and successfully removed the electric field relaxation at the tip during the focusing operation. The anode current of about 1.9 mu A was maintained for the VDG-FEA with the height of the focusing electrode relative to the extraction electrode, hf=-470 nm, even in applying 5 V to the focusing electrode, and the current was 84.4 times larger, compared with the sample with hf=220 nm under the same focusing condition. It was found that the amitted electrons returned back to the extraction electrode by the potential barrier caused by the low focusing potential below 3 V in every sample. (C) 2009 American Vacuum Society. [DOI: 10.1116/1.3093891]