G-ReRAM scientists succeeded to decode new processes in oxide-based ReRAM cells
Modification of the interfaces can significantly influence the behaviour of VCM-type ReRAM cells. If graphene is deposited at the Ta/TaOx interface the device Ta/G/TaOx/Pt shows a transition from VCM to ECM mode. Responsible for the observed phenomena is the mobility of the Ta-ions, that also contribute to the resistive switching. To this surprising result come the G-ReRAM scientists. Ta can also form metallic filaments or Ta-ions can enrich TaOx matrix acting as donors (that are more effective than the oxygen vacancies). Atomic switches, based on cation movement was demonstrated by STM experiment with TaOx, TiOx and HfOx.
Graphene, and also thin layers of amorphous carbon suppress the oxygen reaction and formation of TaOx at the Ta/TaOx interface. In this way only the ECM mode of switching can be clearly observed. Without the barrier layer VCM and ECM co-exist.
For first time redox peaks in VCM systems are reported, thus verifying the electrochemical nature of the resistive switching. The effects of moisture on the resistive switching in VCM cells is demonstrated.
The original papers can be found in:
Nature Nanotechnology: http://www.nature.com/nnano/journal/vaop/ncurrent/full/nnano.2015.221.html
Advanced Materials: http://onlinelibrary.wiley.com/doi/10.1002/adma.201502574/full