Graphene/h-BN Heterostructures for Vertical Architecture of RRAM Design

The development of RRAM is one of the mainstreams for next generation non-volatile memories to replace the conventional charge-based flash memory. More importantly, the simpler structure of RRAM makes it feasible to be integrated into a passive crossbar array for high-density memory applications. By stacking up the crossbar arrays, the ultra-high density of 3D horizontal RRAM (3D-HRAM) can be realized. However, 3D-HRAM requires critical lithography and other process for every stacked layer, and this fabrication cost overhead increases linearly with the number of stacks. Here, it is demonstrated that the 2D material-based vertical RRAM structure composed of graphene plane electrode/multilayer h-BN insulating dielectric stacked layers, AlO_x/TiO_x resistive switching layer and ITO pillar electrode exhibits reliable device performance including forming-free, low power consumption (P_set = ~2 μW and P_reset = ~0.2 μW), and large memory window (>300). The scanning transmission electron microscopy indicates that the thickness of multilayer h-BN is around 2 nm. Due to the ultrathin-insulating dielectric and naturally high thermal conductivity characteristics of h-BN, the vertical structure combining the graphene plane electrode with multilayer h-BN insulating dielectric can pave the way toward a new area of ultra high-density memory integration in the future.