Modulating the Anionic-Electronic Transport Kinetics to Trigger Memristance for Resistive Switching Non-Volatile Memories: New Materials, Structering and Methods

Bipolar resistive switches were recently proposed as a new class of non-volatile switches capable of reading, writing and erasing memory information by switching non-linearly between low- and high-resistance values by application of mV voltage pulses in the ns range. In the last years, resistive switching has been reported for various classes of materials ranging from sulfides to oxides. Despite their promises oxide-based resistive switches are rarely connected in their diffusion kinetics and constants to the memristive device performance characteristics under bias. In particular, models to describe the mixed anionic-electronic defect contributions for two-carrier systems are missing; this difficults the material selection criteria for best performing devices beyond classic gate oxide selection. Firstly, we report on how to probe carrier diffusion characteristics and memristance for mixed anionic-electronic resistive switches and their oxide materials for the newly proposed Memristor-based Cotrell analysis.  For this, we fabricated 2-terminal Pt|SrTiO_3-δ|Pt cross-bar array structures as a model system in terms of its mixed defects which show stable and reproducible resistive switching. Secondly, new material engineering of oxides are discussed to control resistive switching device properties like retention, R_on/R_off ratios and power consumption by "interfacial strain engineering of mixed conducting oxide" is reported. Lattice strain engineering using heterostructures at internal interfaces can be used to tune material properties in micro-dots as new resistive switching archiectures far beyond the change accessible by doping. We exemplify the switching characteristics based on either comprsively or tensily strained Gd_0.1Ce_0.9O_2-x heterolayers by Er₂O₃ or Sm₂O₃ monolayer modulation, respectively. Thirdly, the role of grain boundaries is discussed for epitaxially and nm-roughness grown LaFeO₃ thin film resistive switches with controlled defect levels. We compliment classic resistive switching tests characterizing the near order Raman vibrational (ionic bonding), direct and non-linear optic spectroscopy techniques (electronic contributions).