Dielectric breakdown of polymer films containing metal clusters

Abstract

Thin films of gold-containing plasma-polymerized tetrafluoroethylene were prepared in an rf glow discharge. The films thus obtained showed a wide range of conductivities from insulating ( ρ>1016 Ω cm) to metallic ( ρ∼3×10-6 Ω cm), depending on plasma conditions during synthesis. The synthesis of the polymer is described in detail since it presents several new aspects. The structure and composition of the films were investigated by x-ray photoelectron spectroscopy and transmission electron microscopy. Studies of current-voltage characteristics in the dielectric regime, i.e., below electrical percolation, show that the conduction is volume limited (Poole-Frenkel effect) in non-gold-containing films, and characterized by a bistable switching behavior for gold-rich films. Dielectric breakdown measurements were realized on self-healing metal-insulator-metal structures. The Weibull analysis of breakdown voltages and a statistical treatment of times to breakdown under constant stress give, respectively, the nominal breakdown field E0 and the specific breakdown field Ec. These two sets of data follow similar functional behavior as a function of metallic volume fraction in the films. Surprisingly, the breakdown-field values remain relativity high up to the percolation concentration.