Solution Processed Silver Sulfide Thin Films for Filament Memory Applications

Permission to make digital or hard copies of all or part of this work for personal or classroom use is granted without fee provided that copies are not made or distributed for profit or commercial advantage and that copies bear this notice and the full citation on the first page. To copy otherwise, to republish, to post on servers or to redistribute to lists, requires prior specific permission. Filament Memories based on resistive switching have been attracting attention in recent years as a potential replacement for flash memory in CMOS technology and as a potential candidate memory for low-cost, large-area electronics. These memories operate at low voltages with fast switching speeds. These devices are based on ionic conduction through an electrolyte layer and differ fundamentally in operation from conventional flash memory, which is based on the field effect transistor. To facilitate development of this technology, effects of film structure on ionic and electronic conducting properties and the filament formation processes must be studied. In this work, silver sulfide, a mixed ionic-electronic conductor, is used as a model material for studying the solution processing of filament memories, and to study the impact of film structure on conducting and switching properties. Three different solution processing methods are investigated for depositing silver sulfide: sulfidation of elemental silver films, and sintering of two types of silver sulfide nanoparticles. Effects of nanoparticle sintering conditions on electrolyte structured and mixed conducting properties are investigated by a combination of X-ray diffraction, electrical impedance spectroscopy and thermo-gravimetric analysis. Impact of forming voltage and time on filament morphology is examined to provide an overall view of the impact of electrical and material parameters on device operation.