3D imaging of filaments in organic resistive memory devices

• ToF-SIMS 3D imaging provided direct characterization of conductive filaments organic re-RAMs.
• The switching mechanism is driven by filament formation and local rupture.
• We evidenced the diffusion of small metal NPs by X-STEM and XPS depth profiling.
• Indium counter drift from the bottom ITO bottom electrode was identified.

Filaments in organic and hybrid resistive memories are studied by combining advanced characterization techniques. Model ITO/polymer/Ag devices based on a cross-linked polystyrene layer, are investigated with XPS and ToF-SIMS depth profile analysis to provide a quantitative 3D spectroscopy showing conductive filaments forming between the two metal electrodes. Filament formation mechanisms are discussed by comparing ToF-SIMS reconstructions from pristine and electrically operated devices and by analyzing the drift and diffusion of metal cluster by cross-sectional STEM. Filaments are shown to form by the drift of silver from tips like structures which are formed during the top electrode deposition and the counter drift of indium from the ITO. The switching mechanism is interpreted in terms of reversible activation/inactivation of the same conductive path.

ToF-SIMS 3D imaging on a pristine and cycled ITO/PPS/Ag organic non-volatile memory device showing the filamentary switching mechanism by field assisted diffusion of silver (red) and indium (green).Figure optionsDownload as PowerPoint slide