guest ::
%0 Thesis %A La Torre, Camilla %T Physics-based compact modeling of valence-change-based resistive switching devices %I Rheinisch-Westfälische Technische Hochschule Aachen %V Dissertation %C Aachen %M RWTH-2019-07614 %P 1 Online-Ressource (ix, 164 Seiten) : Illustrationen %D 2019 %Z Veröffentlicht auf dem Publikationsserver der RWTH Aachen University %Z Dissertation, Rheinisch-Westfälische Technische Hochschule Aachen, 2019 %X The demand for energy-efficient, fast, and small electronic memories is steadily rising in today's information technology. Redox-based resistive switching memories (ReRAM) based on the valence change mechanism (VCM) are a promising candidate for high-density data storage, neuromorphic computing, and logic-in-memory computing applications. Resistive switching memories are two-terminal devices whose physical storage principle relies on the change of the electrical resistance. The nonvolatile resistance state can be switched reversibly between at least two different levels by applying appropriate voltage signals. VCM-type memory cells are composed of a mixed ionic-electronic conducting oxide that is sandwiched between two electrodes. Typically, the two electrodes consist of metals with different work functions and oxygen affinities. Bipolar resistive switching is induced by the migration of ionic defects (oxygen vacancies) and a concurrent valence change of the cation sublattice. To enable future design of memory, logic, and neuromorphic computing applications, circuit simulations based on precise and predictive compact models are crucial. Physics-based compact models do not use fitting parameters, but stick to material and geometrical parameters. Their great advantage lies in the power to predict the switching behavior upon changes in the input voltage amplitude and initial values. Compact models are developed based on the knowledge gained from more detailed, space-resolved models. Despite intensive research, open questions still remain, in particular, regarding the limiting physical mechanisms that are involved in resistive switching. In this thesis, three physics-based compact models with different levels of detail are developed to study various switching effects in filamentary VCM-type ReRAM devices. All simulations are performed using MATLAB. Compact model 1.0 describes bipolar switching based on the drift of oxygen vacancies along a filament. The vacancies act as donors causing a change in conductivity, and thereby resistance, by modulating the Schottky barrier at the metal/oxide interface and the donor concentration in the adjacent oxide region. In compact model 1.5, the ion migration process is extended to include diffusion. Moreover, the modulation of both metal/oxide junctions is considered, allowing the model to cover complementary switching. In compact model 2.0, oxygen exchange at the metal/oxide interfaces is added enabling the simulation of the initial forming step as well as different endurance and retention behaviors. In addition to standard bipolar and complementary switching, a second bipolar switching mode is also covered. For the three models, the used assumptions and the model limits are emphasized to allow a correct interpretation of the simulation results. Various parameter studies are performed to identify the influence of material parameters, voltage excitation, and current compliance on the switching. This understanding will help to control the occurrence/suppression of intended/unintended effects by material choice or external excitation design. %F PUB:(DE-HGF)11 %9 Dissertation / PhD Thesis %R 10.18154/RWTH-2019-07614 %U https://publications.rwth-aachen.de/record/765751