Use of Millikan–Lauritsen plots, rather than Fowler–Nordheim plots, to analyze field emission current-voltage data

In the late 1920s, two forms of data plot were used to analyze the current-voltage (i-V) data obtained in experiments on cold field electron emission (CFE). Millikan–Lauritsen (ML) plots have the form [ln{i} versus 1/V]; Fowler–Nordheim (FN) plots have the form [ln{i/V2} versus 1/V]. In both cases common logarithms may be used instead. For historical reasons, it has become customary to use FN plots; but recent mathematical developments in CFE theory made these historical reasons less valid than they formerly were. ML plots are in fact easier to understand and use, and are more flexible when it is wanted to make corrections for all physical sources of voltage dependence in the data, or to estimate uncertainties in derived parameter values when the precise forms of voltage dependences are not known. This paper summarizes historical and recent background and argues that ML plots should now replace FN plots as the basic method of analyzing CFE i-V data (or related data involving current densities and/or fields). A formula for the interpretation of ML plot slopes is presented and discussed, and examples are given of its use.