How Accurate is a Field Emission Experiment?

Even though the Fowler-Nordheim theory is almost 100 years old, the characterization of field emitters is not always very reliable. A common belief in the community is that the estimated values of the work function, emission area and field enhancement factor are probably correct within a few percent or below as the uncertainty in these values is rarely mentioned. We will show that even for a high-quality linear Fowler-Nordheim plot the inaccuracy in the extracted parameters is more of the order of 50 %.