Optimization of ion-track etching and electrochemical Cu nanocone deposition for field emission cathodes

We have fabricated patch-structured nanocone (NC) cathodes by using asymmetrically etched ion-track membranes which were metallized and fixed on flat holders. The conical channels of these templates were filled by potentiostatic copper deposition resulting in freestanding Cu-NC of ~ 28 μm length, ~ 3 μm base, and 160-240 nm tip diameter. Fairly homogeneous and well-aligned field emission from all patches was obtained due to the high NC (10⁵ cm^-2) and emitter densities (~ 3/patch). Local measurements of selected spots and patches show distinct current jumps at μA levels. SEM images of the processed areas reveal morphological changes proving a successive destruction of single Cu-NCs. Nevertheless, improved current values of ~ 300 μA at reduced fields of 30-50 V/μm have been achieved for the best Cu-NC patches.