An Atomistic Model of Field-Induced Resistive Switching in Valence Change Memory

Abstract

In valence change memory (VCM) cells, the conductance of an insulating switching layer is reversibly modulated by creating and redistributing point defects under an external field. Accurately simulating the switching dynamics of these devices can be difficult due to their typically disordered atomic structures and inhomogeneous arrangements of defects. To address this, we introduce an atomistic framework for modeling VCM cells. It combines a stochastic kinetic Monte Carlo approach for atomic rearrangement with a quantum transport scheme, both parametrized at the ab initio level by using inputs from density functional theory. Each of these steps operates directly on the underlying atomic structure. The model thus directly relates the energy landscape and electronic structure of the device to its switching characteristics. We apply this model to simulate field-induced nonvolatile switching between high- and low-resistance states in a TiN/HfO2/Ti/TiN stack and analyze both the kinetics and stochasticity of the conductance transitions. We also resolve the atomic nature of current flow resulting from the valence change mechanism, finding that conductive paths are formed between the undercoordinated Hf atoms neighboring oxygen vacancies. The model developed here can be applied to different material systems to evaluate their resistive switching potential, both for use as conventional memory cells and as neuromorphic computing primitives.

Quantum Transport Properties of Nanosized Ta2O5 Resistive Switches: Variable Transmission Atomic Synapses for Neuromorphic Electronics

“…There are several microscopic processes that can cause filamentary RS behavior in valence change memories. Besides the migration and valence change of oxygen vacancies, 48 the movement of metal cations can also account for RS, according to first-principle simulations 49−51 and experiments. 36 The inset of Figure 1b shows the low-bias conductance values in the LCS and HCS of the hysteretic I(V) characteristics demonstrating fine analogue tunability in the 4G 0 −7G 0 range.…”

Resistive Switching Devices for Neuromorphic Computing: From Foundations to Chip Level Innovations

“…The addition of an oxygen-deficient ZnO layer provided additional oxygen ion migration pathways as well as an oxygen reservoir, resulting in an increased ON/OFF ratio as well. Theoretical modeling attempts to understand the switching mechanism in VCM devices have been reported recently by M. Kaniselvan et al [ 47 ]. They used a combination of stochastic kinetic Monte Carlo methods in combination with quantum transport models with inputs from density functional theory calculations to investigate the effect of interface interactions between the oxide layer and the metal atom.…”

Structure and assembly studies of two planar Dy(iii) single molecule magnets with double relaxations

“…In the era of the rapid development of information technology, single-molecule magnets (SMMs) have received great attention as molecule-based magnetic materials with potential applications in fields such as ultra-high-density data storage, 1 quantum computing, 2 and molecular spintronics. 3,4 Compared with transition metal ions, lanthanide ions have unquenched orbital angular momentum and strong spin–orbit coupling with their internal 4f electrons shielded by 5s and 5p electrons, 5,6 which easily favor strong magnetic anisotropy.…”