Hafnium oxide/graphene/hafnium oxide-stacked nanostructures as resistive switching media

Abstract

Thin HfO2 films were grown by atomic layer deposition on chemical vapor-deposited large-area graphene. The graphene was transferred, prior to the deposition of the HfO2 overlayer, to the HfO2 bottom dielectric layer pregrown on the Si/TiN substrate. Either HfCl4 or Hf[N(CH3)(C2H5)]4 was used as the metal precursor for the bottom layer. The O2 plasma-assisted process was applied for growing HfO2 from Hf[N(CH3)(C2H5)]4 also on the top of graphene. To improve graphene transfer, the effects of the surface pretreatments of the as-grown and aged Si/TiN/HfO2 substrates were studied and compared. The graphene layer retained its integrity after the plasma processes. Studies on resistive switching on HfO2-graphene-HfO2 nanostructures revealed that the operational voltage ranges in the graphene-HfO2 stacks were modified together with the ratios between high- and low-resistance states.