Communication-hourglass-shaped metal-filament switching device with multi-layer (AlO_X/TiO₂) oxide electrolytes

This paper proposes using hourglass-shaped metal filaments to improve the ON/OFF resistance ratio and retention characteristics of switching devices used in reconfigurable logic applications. These filaments are obtained by controlling the Cu-ion mobility in multi-layer oxide electrolytes. By adopting an upper AlO_X and lower TiO₂ electrolyte layers with respectively low and high Cu-ion mobility, we could form hourglass-shaped filaments as a result of suppressed Cu-ion injection and enhanced filament lateral growth. The hourglass-shaped metal filaments induced local Joule heating at the filament constriction, thus accelerating RESET operations. We confirmed that, as a result, Cu/AlO_X/TiO₂/W devices show high ON/OFF resistance ratios (>10⁶) and ∼10-year retention properties at 80°C.