Electroforming processes for platinum nanoisland thin films

Abstract

An investigation of the electroforming processes for platinum discontinuous thin films is detailed. Current–voltage characteristics, for metal nanoislands deposited by sputtering, were obtained in vacuum and air and typically showed voltage-controlled negative resistance (VCNR) behaviour. The current maximum shifted with the electrode separation. Electroforming under high current density regimes was non-regenerative as samples showed irreversible resistance changes. SEM examination of the film revealed a change in the metal microstructure. Such modifications arise as a result of the current flowing through the film inducing electro and thermal migration. Current-induced effects were studied by modelling the metal nanoisland (MN) layer as an array of cubic cells. Plots of current distribution showed that hot-spots develop along conductive paths. Electromigration combined with resistive heating can lead to progressive destruction of current channels at these hot-spots. Hence, current profiles and SEM micrographs were interpreted as evidence of a ‘macroscopic’ electrical breakdown of sample conduction due to microstructural modifications of the thin film. The reduction of ohmic component and consequent resistive heating along the current channels prevented the metal migration and stable current profiles were obtained.