Resistance switching in Cu/SiO2-based conductive-bridging random access memories is studied under voltage and current-driven modes. These two modes are used to study memory cycling and time-dependent switching. Voltage-current (V-I) cycles (logarithmic current ramp) are compared to I-V cycles (linear voltage ramp). The Off-On transition in V-I cycles is governed by device capacitance. The Off-On switching time (in the 10−1–103 s range) was studied under constant voltage and constant current stresses. The switching time varies as exp(V0/V) and as 1/I. Switching kinetics is discussed considering a Fowler–Nordheim tunneling injection law and a field-induced nucleation theory.
Pt/NiO-based devices are promising candidates for the next generation of resistive random access memories (RRAMs). X-ray (XPS) and ultraviolet (UPS) photoemission are performed to investigate the chemical and electronic properties of this stack. After resistive switching of the nickel oxide, the as-deposited and switched areas are compared in situ. The surface of the conductive area is characterised by a higher oxygen content as well as an enhancement of Ni 3+ oxidation state, which can be related to defects such as Ni vacancies. The results are compatible with a bias-induced diffusion of O 2− towards the anode, and a migration of Ni 2+ towards the cathode. The NiO electron affinity is estimated to be 1.6 eV by UPS in the OFF state, leading to a Pt/NiO barrier height of 3.6 eV.
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