SrRuO3 (SRO) thin films have been grown on a (001)-oriented SrTiO3 substrate with Sr3Al2O6 (SAO) buffer layers using pulsed laser deposition. X-ray diffraction results reveal that the epitaxial strain of SRO changes from compressive to relaxed or tensile ones by tuning the thickness of the SAO buffer layer (tSAO). We have demonstrated that the variation of strain has a strong influence on the microstructure and electrical and magnetic properties of SRO. When tSAO < 10 nm, the epitaxial strain is relaxed and the SRO film possesses higher Curie temperature resembling that of SRO bulk. Upon further increasing tSAO ≥ 10 nm, the SRO films are subjected to tensile strain, showing a typical step-and-terrace surface and coherent epitaxy characteristic on the SAO buffer layer. The electrical and magnetic properties of SRO are very sensitive to buffer layer-controlled epitaxial strain. The tensile strained SRO films show quite different electrical transport properties at low temperature, i.e., appearance of metal-insulator transition and positive magnetoresistances and the absence of non-Fermi-liquid behavior. Additionally, magnetic anisotropy is found in both the tensile and the compressively strained SRO, while the strain-relaxed film shows isotropic magnetization. Based on the electrical and magnetic properties, a phase diagram of SRO on the SAO buffer layer has been constructed.

Memristors have been intensively studied in recent years as promising building blocks for next-generation nonvolatile memory, artificial neural networks and brain-inspired computing systems. However, most memristors cannot simultaneously function in extremely low and high temperatures, limiting their use for many harsh environment applications. Here, we demonstrate that the memristors based on high-Curie temperature ferroelectrics can resolve these issues. Excellent synaptic learning and memory functions can be achieved in BiFeO 3 (BFO)-based ferroelectric memristors in an ultra-wide temperature range. Correlation between electronic transport and ferroelectric properties is established by the coincidence of resistance and ferroelectricity switch and the direct visualization of local current and domain distributions. The interfacial barrier modification by the reversal of ferroelectric polarization leads to a robust resistance switching behavior. Various synaptic functions including long-term potentiation/ depression, consecutive potentiation/depression and spike-timing dependent plasticity have been realized in the BFO ferroelectric memristors over an extremely wide temperature range of −170 °C∼300 °C, which even can be extended to 500 °C due to the robust ferroelectricity of BFO at high temperatures. Our findings illustrate that the BFO ferroelectric memristors are promising candidates for ultra-wide temperature electronic synapse in extreme or harsh environments.

Optically triggered nonvolatile memory is demonstrated in an indium tin oxide (ITO)/BiFeO 3 (BFO)/SrRuO 3 (SRO) heterostructure. In contrast to conventional devices where optical excitations typically enhance conduction, the prepared device exhibits a pronounced decrease in conductivity (1 × 10 −4 ) after laser illumination at wavelengths of 405, 532, and 1064 nm. Also, the negative optoelectronic memory could be reset using optical stimuli and set using an electrical pulse. This characteristic was suppressed through annealing in an oxygen-rich atmosphere, and then reappeared after annealing in an oxygen-poor atmosphere. Systematic investigations on the transport and dielectric properties show that the observed controllable optical/ electrical resistance switching behavior is attributed to a modulation of the potential profile at the ITO/BFO interface due to optical and electrical excitations. These observations indicate a feasible avenue for future generations of nonvolatile optoelectronic memory devices.

We report a reversible transition between filamentary and ferroelectric resistive switching in BaTiO3/SmNiO3 heterostructures.