Thermal stability and data retention of resistive random access memory with HfOx/ZnO double layers

As an industry accepted storage scheme, hafnium oxide (HfOx) based resistive random access memory (RRAM) should further improve its thermal stability and data retention for practical applications. We therefore fabricated RRAMs with HfOx/ZnO double-layer as the storage medium to study their thermal stability as well as data retention. The HfOx/ZnO double-layer is capable of reversible bipolar switching under ultralow switching current (< 3 mu A) with a Schottky emission dominant conduction for the high resistance state and a Poole-Frenkel emission governed conduction for the low resistance state. Compared with a drastically increased switching current at 120 degrees C for the single HfOx layer RRAM, the HfOx/ZnO double-layer exhibits excellent thermal stability and maintains neglectful fluctuations in switching current at high temperatures (up to 180 degrees C), which might be attributed to the increased Schottky barrier height to suppress current at high temperatures. Additionally, the HfOx/ZnO double-layer exhibits 10-year data retention @85 degrees C that is helpful for the practical applications in RRAMs.