Metal-Polymer-Vacuum Interface Formation in the High Static Electric Field

Abstract

The phenomenon of an electron emission from cold metals in high static electric fields was observed for the first time by Lilienfeld in 1922 [1]. Six years later Fowler and Nordheim [2] derived their well-known formula for the field emission current analyzing the electron tunnelling through the potential barrier. In order to understand the phenomenon of an electron transport through the interface between two solids (metal-metal, metal-semiconductor, etc.) the idea of interband tunnelling was proposed by Zener [3]. According to him interband tunnelling should occur between a filled band to a next higher unfilled band by the application of the electric field. In this model the energy gap in the electronic band stucture of the solid could be treated in the manner of a potential barrier called usually the Schottky barrier [4]. Its height is simply the difference between the metal Fermi level and the bottom of the conduction band of the semiconductor (insulator). In general, the formation of the interface potential barrier is strongly determined by the position of the Fermi level at the contact. Bardeen [5] was the first who pointed out the significant role of the intrinsic electronic surface states (gap states) in the stabilization (pinning) process of the Fermi level at such interfaces (Bardeen model [6]).