Electrochemical breakdown in thin Nb2O5 films

Observations are presented on breakdown during the galvanostatic growth of niobium pentoxide in acid medium. The role played by electrolyte parameters, such as acid concentration and transport through the solution of electron donor species, is examined. The intrinsic properties of the oxide film and a correlation between the inner film and its thickness are discussed with regard to impact ionization and the avalanche breakdown model. Experiments using electrochemical copper reduction on the surface of the film suggest that electronic conduction through filamentary high conduction paths is responsible for the localization of the observed breakdown spots.