Physical models of size-dependent nanofilament formation and rupture in NiO resistive switching memories

Abstract

NiO films display unipolar resistance switching characteristics, due to the electrically induced formation and rupture of nanofilaments. While the applicative interest for possible use in highly dense resistance switching memory (RRAM) is extremely high, switching phenomena pose strong fundamental challenges in understanding the physical mechanisms and models. This work addresses the set and reset mechanisms for the formation and rupture of nanofilaments in NiO RRAM devices. Reset is described in terms of thermally-accelerated diffusion and oxidation processes, and its resistance dependence is explained by size-dependent Joule heating and oxidation. The filament is described as a region with locally-enhanced doping, resulting in an insulator-metal transition driven by structural and chemical defects. The set mechanism is explained by a threshold switching effect, triggering chemical reduction and a consequent local increase of metallic doping. The possible use of the observed resistance-dependent reset and set parameters to improve the memory array operation and variability is finally discussed.

Pulse-induced resistive and capacitive switching in TiO2 thin film devices

“…As such, the active core of our prototypes only undergoes a reduction, i.e., from TiO 2 to TiO 2Àx , after the application of a number of pulses that induce a cumulative thermally driven mechanism (Joule heating Refs. [34][35][36][37][38]. In consequence, the first resistance and capacitance switching event took place after 37 continuous applied pulses with the resistance switching from a HRS to a LRS and the capacitance from a LCS to HCS.…”

“…On the other hand, for later switching events, when the chemistry of the active core is altered enough, the accumulated energy is dissipated by Joule heating, which causes the rupture/re-formation of conductive filaments (Refs. [34][35][36][37][38].…”

Low-power resistive random access memory by confining the formation of conducting filaments

“…The resistance R of a semiconducting material as a function of temperature follows R = R 0 e E AC kT , where E AC is the thermal activation energy, R 0 is the resistance at the infinite temperature, T is the absolute temperature, and k is the Boltzmann constant. 31 The Arrhenius plots of the resistance as a function of 1/T show that the thermal activation energy of HRS is 74 meV and that of LRS is 34 meV (Fig. 3(c)).…”

Phenomenological modeling of memristive devices

“…For example, some models focus on specific aspects of the memristive behavior, e.g., static equation only [4], or a particular aspect of switching dynamics [13,19,21,43], and hence are incomplete. Others are derived assuming very simple physical models [6,18,48] and therefore could not accurately predict experimental behavior-see also comprehensive reviews of such models in Refs.…”