Nanofilament Dynamics in Resistance Memory: Model and Validation

Abstract

Filamentary resistive random-access memory (ReRAM) employs a single nanoscale event to trigger a macroscopic state change. While fundamentally it involves a gradual electrochemical evolution in a nanoscale filament that culminates in an abrupt change in filament's resistance, understanding over many length and time scales from the filament level to the device level is needed to inform the device behavior. Here, we demonstrate the nanoscale elements have corresponding elements in an empirical equivalent circuit. Specifically, the filament contains a variable resistor and capacitor that switch at a critical voltage. This simple model explains several observations widely reported on disparate filamentary ReRAMs. In particular, its collective system dynamics incorporating the power-law time-relaxation of the variable capacitance can accurately account for the responses of variously sized single-filament HfOx ReRAMs to DC/quasi-static and pulse electrical stimulation, exhibiting Avrami-like switching kinetics and a pulse-rate dependence in on/off voltages.

Determining the Electrical Charging Speed Limit of ReRAM Devices

“…The simulation results so far indicate the possibility of the heating to occur only within few picoseconds [18] or several nanoseconds [6]. The electrical charging time depends strongly on the VCM device's area [27].…”

“…The incoming and reflected pulses superimpose, doubling the effectively applied voltage at the VCM device. The timescale at which this doubling occurs was so far only estimated by circuit based models [15], [26], [27].…”

“…The impact of the circuit on the switching kinetics has already been studied with circuit models, in which also the effective voltage at the device was calculated [27] or simulated [15], [26]. Torrezan et al also conducted frequency domain measurements up to 20 GHz [15].…”

Black Phosphorus Quantum Dots with Tunable Memory Properties and Multilevel Resistive Switching Characteristics

“…Resistive random access memories (RRAMs), with a typical metal–insulator–metal architecture, exhibit great potential for the construction of future nonvolatile memories because of their high scalability, substantial endurance, long retention time, excellent memory performance, and low operating energy . The operation of RRAMs relies on the change in resistance between the high resistance state (HRS) and the low resistance state (LRS).…”

Scalability of voltage-controlled filamentary and nanometallic resistance memory devices

“…For the filamentary RRAM, we fabricated Ti/HfO 2 /Pt devices by placing a 10 nm-thick atomic-layer-deposited HfO 2 film between a Pt bottom electrode and a Ti top electrode of various sizes. After being formed by a negative voltage, without compliance, to HRS, 11 it was switched-on at a positive voltage and switched-off at a negative voltage as shown in Figure 1a.…”