Origin of the Slope-Intercept Linear Relationship in Field Emission

Field emitters are often analyzed by linear fitting of a Fowler-Nordheim plot. The fitted slopes and intercepts can show a strong correlation, but its origin remains unclear. We propose a simple model showing that this correlation is due to fluctuations in the slope and the fact that the data in the abscissa of the Fowler-Nordheim plot are far from the origin. We show that this explanation correctly predicts other results in the field emission literature.