Theory of electron emission from atomically sharp metallic emitters in high electric fields
A systematic theoretical investigation of the effect of tip geometry on the field emission current voltage characteristics from atomically sharp metallic field emitters is presented. A free electron model is used for the metal emitters with non-planar geometries in studying the dependence of the current density on tip geometry, local field, and temperature. The classical image interaction is derived exactly for the metal emitters modeled as cones, paraboloids, hyperboloids and sphere on cones. The classical image interaction for these non-planar emitter geometries is diminished in magnitude relative to the planar image interaction. The bias potential for the model emitter modifies the shape of the tunneling barriers, and the resulting form predicts a dramatically enhanced current relative to the classical Fowler-Nordheim result. The transmission coefficients for the surface potential barriers are evaluated within the WKB approximation. The current-voltage characteristics are calculated for these models using the kinetic formulation of the current density integral. The calculated results do not exhibit the straight line behavior predicted by the Fowler-Nordheim model for field emission from a planar surface. The effects of emitter curvature on electron emission in combined high fields and elevated temperature are examined. An analytic expression for the J(V) characteristics of a prototype sharp emitter is derived which exhibits explicitly the dependence of the current density on geometric and material parameters. The adequacy of a [beta]-factor in the conventional planar model F-N equation to account for emitter curvature is examined. The use of such an F-N equation is incorrect when applied to sharp emitters (r[sub t] [le] 10nm) and will lead to spurious results when used to extract information such as field values or emitting area from experimental F-N curves. The effect of tip geometry on the Nottingham energy exchange and temperature stability is studied.
- Research Organization:
- Pennsylvania State Univ., University Park, PA (United States)
- OSTI ID:
- 7112210
- Resource Relation:
- Other Information: Thesis (Ph.D.)
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
SUPERCONDUCTIVITY AND SUPERFLUIDITY
METALS
ELECTRON EMISSION
TUNNEL EFFECT
CURRENT DENSITY
ELECTRIC FIELDS
FOWLER-NORDHEIM THEORY
MATHEMATICAL MODELS
SOLID STATE PHYSICS
TEMPERATURE DEPENDENCE
WKB APPROXIMATION
ELEMENTS
EMISSION
PHYSICS
665400* - Quantum Physics Aspects of Condensed Matter- (1992-)