Electro-thermal transport in disordered nanostructures: a modeling perspective

Ducry, Fabian; Aeschlimann, Jan; Luisier, Mathieu

doi:10.1039/d0na00168f

Cited by 9 publications

(4 citation statements)

References 102 publications

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“…The coupling between our quantum transport solver and CP2K is outlined in detail in ref. 39 . The Hamiltonian and overlap matrices required by NEGF were exported from CP2K.…”

Section: Quantum Transport Simulation Methodsmentioning

confidence: 99%

An ab initio study on resistance switching in hexagonal boron nitride

et al. 2022

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Two-dimensional materials have been widely investigated to implement memristive devices for data storage or neuromorphic computing applications because of their ultra-scaled thicknesses and clean interfaces. For example, resistance switching in hexagonal boron nitride (h-BN) has been demonstrated. This mechanism is most of the time attributed to the movement of metallic ions. It has however also been reported when h-BN is contacted with two inert electrodes such as graphene or Pt. We suggest here that the switching mechanism of the latter devices, which has not yet been clearly established, relies on locals change of the electronic structure of h-BN as caused by atomic defects, e.g., multi-vacancies. This class of intrinsic h-BN defects can create electrically controllable interlayer bridges. We use a combination of hybrid density functional theory and the Non-equilibrium Green’s function formalism to show that a single interlayer bridge resulting from the presence of a trivacancy in a graphene/h-BN/graphene stack leads to a switching voltage of ~5 V and a high-to-low resistance ratio >100. Both values lie within the reported experimental range and thus confirm the likelihood that intrinsic defects play a key role in the resistance switching of h-BN in contact with inert electrodes.

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“…The coupling between our quantum transport solver and CP2K is outlined in detail in ref. 39 . The Hamiltonian and overlap matrices required by NEGF were exported from CP2K.…”

Section: Quantum Transport Simulation Methodsmentioning

confidence: 99%

An ab initio study on resistance switching in hexagonal boron nitride

et al. 2022

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“…To generate H cp2k and S cp2k , the orbitals for all the atoms in the device are described by a short-range SZV basis set, which was found sufficient to capture trends in the final transmission (see ref 69). Using a higher number of basis functions per orbital would lead to more accurate results for a larger transport energy window, but is computationally unfeasible for the system sizes considered here.…”

Section: Methodsmentioning

confidence: 99%

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

2023

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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.

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“…Coupled electron-phonon transport with atomistic NEGF was first achieved for molecular bridge junctions using an empirical basis set for both particle types [32]. A fully ab initio treatment of both electrons and phonons was proposed later for 3-D metal-oxide-metal heterostructures [33]. The same has not yet been done for coupled electron-photon transport.…”

Section: Coupled Fermion-boson Transportmentioning

confidence: 99%

“…The search for reliable memristive material stacks has motivated the application of the atomistic DFT+NEGF method to other non-volatile resistive switching systems as well. For example, a recent work by Ducry et al [33] coupled electron and phonon transport at the ab initio level to determine the influence of Joule heating on the performance of Cu-SiO 2 -W CBRAM cells.…”

Section: B Memory Cellsmentioning

confidence: 99%

Atomistic Simulation of Nanoscale Devices

Lee

Cao

Luisier

2023

IEEE Nanotechnology Mag.

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Device simulation is nowadays fully integrated into the production tool chain of transistors. The geometry of the latter can be carefully optimized, possible design pitfalls can be identified early on, and the obtained experimental data can be analyzed in detail thanks to state-of-the-art technology computer aided design tools. However, on the one hand, the dimensions of transistors are reaching the atomic scale. On the other hand, novel functionalities (e.g., light emission/detection) and materials, for example III-V semiconductors, are being added to silicon-based chips. To cope with these challenges it is crucial that device simulators go beyond classical theories, pure electronic transport, and continuum models. The inclusion of quantum mechanical phenomena, electrothermal effects, and light-matter interactions in systems made of thousands of atoms and of various materials has become critical. In this paper, we review one approach that satisfies all these requirements, the Non-equilibrium Green's Function (NEGF) formalism, focusing on its combination with ab initio bandstructure models. The NEGF method allows to treat electrical, thermal, and optical transport at the quantum mechanical level in multi-material, multi-functional devices, without any empirical parameters. Besides advanced logic switches, it can be used to simulate e.g., photo-detectors, thermoelectric generators, or memory cells composed of almost any materials, in the ballistic limit of transport and in the presence of scattering. The key features of NEGF are summarized first, then selected applications are presented, finally challenges and opportunities are discussed.

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Electro-thermal transport in disordered nanostructures: a modeling perspective

Abstract: We review here how molecular dynamics and quantum transport can be combined to shed light on the performance of, for example, conductive bridging random access memories, and we show that electro-thermal effects play a critical role.

Cited by 9 publications

References 102 publications

An ab initio study on resistance switching in hexagonal boron nitride

An ab initio study on resistance switching in hexagonal boron nitride

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

Atomistic Simulation of Nanoscale Devices

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