Fully transparent resistive memory employing graphene electrodes for eliminating undesired surface effects

A ZnO-based transparent resistance random access memory (TRRAM) employs atomic layered graphene exhibiting not only excellent transparency (less than 2% absorptance by graphene) but also reversible resistive switching characteristics. The statistical analysis including cycle-to-cycle and cell-to-cell tests for almost 100 cells shows that graphene plays a significant role to suppress the surface effect, giving rise to the notable increase in the switching yield and the insensitivity to the environmental atmosphere. The resistance variation of high-resistance state of ZnO is greatly suppressed by covering graphene as well. The device reliability investigation, such as the endurance more than 10² cycles and the retention time longer than 10⁴ s, reveals the robust passivation of graphene for TRRAM applications. The obtained insights show guidelines not only for TRRAM device design and optimization against the undesired switching parameter variations but also for developing practically useful applications of graphene.