Nanoscale electrical characterization of trap-assisted quasibreakdown fluctuations in SiO2

Conductive atomic force microscopy has been used to electrically image quasibreakdown sites in thin, native SiO2 films. Local current-voltage spectroscopy reveals, at individual sites, fluctuations in the breakdown current between well-defined conductivity states. Theoretical modeling has been performed to show that conduction through the film is governed by local trap-assisted tunneling, with typically one or two charge traps contributing to conduction through a quasibreakdown site. Our study provides a semi quantitative analysis to characterize the effective trap states that give rise to local random telegraph signals in the oxide film. (C) 2004 American Institute of Physics.