THE ROLE OF GEOMETRIC FIELD ENHANCEMENT FOR THE ENHANCED FIELD EMISSION OF NIOBIUM

We have systematically investigated the 'natural' emission sites of two cm sized samples, which were wet chemical prepared and heated in UHV at 400°C. The changes of the emission parameters due to a deposition of a 16 nm gold layer on one sample were evaluated with respect to the current models for the enhanced field emission process. Comparison of the Fowler-Nordheim parameters βFN and SFN of the emitters with their geometrical field enhancement factors βgeo, which were estimated from high resolution scanning electron microscope analysis, revealed that the observed emitting structures are sharp enough to explain the measured βFN, while the values of SFN do not agree with the geometry. 1