Nanostructures Stacked on Hafnium Oxide Films Interfacing Graphene and Silicon Oxide Layers as Resistive Switching Media.

SiO films were grown to thicknesses below 15 nm by ozone-assisted atomic layer deposition. The graphene was a chemical vapor deposited on copper foil and transferred wet-chemically to the SiO films. On the top of the graphene layer, either continuous HfO or SiO films were grown by plasma-assisted atomic layer deposition or by electron beam evaporation, respectively. Micro-Raman spectroscopy confirmed the integrity of the graphene after the deposition processes of both the HfO and SiO. Stacked nanostructures with graphene layers intermediating the SiO and either the SiO or HfO insulator layers were devised as the resistive switching media between the top Ti and bottom TiN electrodes. The behavior of the devices was studied comparatively with and without graphene interlayers. The switching processes were attained in the devices supplied with graphene interlayers, whereas in the media consisting of the SiO-HfO double layers only, the switching effect was not observed. In addition, the endurance characteristics were improved after the insertion of graphene between the wide band gap dielectric layers. Pre-annealing the Si/TiN/SiO substrates before transferring the graphene further improved the performance.