Description of field emission current/voltage characteristics in terms of scaled barrier field values (f-values)

Abstract

The scaled barrier field f is defined as the local field F that determines a field emission tunneling barrier, divided by the critical field needed to reduce to zero a barrier initially of height (for F=0) equal to the local work-function. The description of field emission current-voltage (I−V) characteristics is more universal, and closer to theory, if measured voltages are reassigned as f-values. This paper describes a simple method for directly converting voltage to f-value, using the slope of a Fowler-Nordheim plot of type ln{I/V2} vs 1/V. A short table of characteristic f-values could be helpful for describing typical emission features such as the emission onset, the onset of emitter degradation, or the onset of space-charge effects. For an old-style metal field emitter of moderate to large apex radius, a table based on the systematic work of Dyke and Trolan [Phys. Rev. 89, 799 (1953)] is given. Tables of this kind, if prepared for different categories of field emitter, could be helpful in emitter comparisons. In another use, different individual emitters in emitter arrays can be thought of as operating at different f-values. The use of f-values seems a simple, additional helpful way of describing field emitter behavior, particularly in technological contexts.