Update on analysis of Fowler-Nordheim plots from nonmetallic emitters

Summary form only given. Some years ago, the author introduced a new method for extracting emission area from Fowler-Nordheim (FN) plots (1999). This is numerically precise only for free-electron metals under specified conditions, but it may be applied as a first approximation to other materials, including carbon-based thin films. Over the last few years, over 200 published carbon-based FN plots have been analysed. This paper presents an update. The general conclusion is that (on average) areas derived from nanotube FN plots are significantly larger (by a factor of order 100) than areas derived from carbon and diamond film FN plots, and that many plots from diamond and carbon thin-films yield area estimates too small to be plausible. The much greater number of plots analysed since this data was first reported thus confirms the latter finding, and again supports (but more strongly) the obvious speculation that, certainly in these cases, either (1) the rate-controlling mechanism is not conventional Fowler-Nordheim-type cold field electron emission, or (2) the theory of the conventional mechanism is not properly formulated for these materials.