Abstract
Measured field electron emission (FE) current–voltage Im(Vm) data are traditionally analysed via Fowler–Nordheim (FN) plots, as versus 1/Vm. These have been used since 1929, because in 1928 FN predicted they would be linear. In the 1950s, a mistake in FN's thinking was found. Corrected theory by Murphy and Good (MG) made theoretical FN plots slightly curved. This causes difficulties when attempting to extract precise values of emission characterization parameters from straight lines fitted to experimental FN plots. Improved mathematical understanding, from 2006 onwards, has now enabled a new FE data-plot form, the ‘Murphy–Good plot'. This plot has the form versus 1/Vm, where η ≅ 9.836239 (eV/ϕ)1/2 and ϕ is the local work function. Modern (twenty-first century) MG theory predicts that a theoretical MG plot should be ‘almost exactly' straight. This makes precise extraction of well-defined characterization parameters from ideal Im(Vm) data much easier. This article gives the theory needed to extract characterization parameters from MG plots, setting it within the framework of wider difficulties in interpreting FE Im(Vm) data (among them, use of ‘smooth planar emitter methodology'). Careful use of MG plots could also help remedy other problems in FE technological literature. It is suggested that MG plots should replace FN plots.
Highlights
Field electron emission (FE) occurs in many technological contexts, especially electron sources and electrical breakdown
A need exists for effective analysis of measured FE current–voltage [Im(Vm)] data, to extract emission characterization parameters
These include: parameters that connect field to voltage; the field enhancement factors (FEFs) often used to characterize large-area field-electron emitters (LAFEs); and parameters relating to emission area and area efficiency
Summary
Field electron emission (FE) occurs in many technological contexts, especially electron sources and electrical breakdown. This, in turn, causes very significant problems of detail and the need for related procedures, when attempts are made to give well-defined precise meanings to the slope and intercept of the straight line fitted to an FN plot of experimental data. These interpretation procedures involve correct choice of fitting point [11,12] and application of a chord correction [12]. If curvature in an FN plot taken from an ideal FE device/system is due to physical reasons (such as small apex radius of curvature, or––with a LAFE––statistical variations in the characteristics of individual emitters), use of an MG plot will not be able to straighten out this kind of curvature, 3 though it should be a useful step forwards
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