Ferroelectric field manipulated nonvolatile resistance switching in Al:ZnO/Pb(Mg1/3Nb2/3)0.7Ti0.3O3 heterostructures at room temperature

Light-activated Multilevel Resistive Switching Storage in Pt/Cs2AgBiBr6/ITO/Glass Devices

High-density Cs₂AgBiBr₆ films with uniform grains were prepared by a simple one-step and low-temperature sol-gel method on indium tin oxide (ITO) substrates. An explicit tristate bipolar resistance switching behavior was observed in the Pt/Cs₂ AgBiBr₆/ITO/glass devices under irradiation of 10 mW/cm² (445 nm). This behavior was stable over 1200 s. The maximum ratio of the high and low resistance states was about 500. Based on the analysis of electric properties, valence variation and absorption spectra, the resistive switching characteristics were attributed to the trap-controlled space charge-limited current mechanism due to the bromine vacancies in the Cs₂AgBiBr₆ layer. On the other hand, it is suggested that the ordering of the Schottky-like barrier located at Pt/Cs₂AgBiBr₆ affects the three-state resistance switching behavior under light irradiation. The ability to adjust the photoelectrical properties of Cs₂AgBiBr₆-based resistive switching memory devices is a promising strategy to develop high-density memory.

Engineering Co Vacancies for Tuning Electrical Properties of p-Type Semiconducting Co3O4 Films

Spinel oxide Co₃O₄ has attracted more and more attention for energy- and environment-related applications. In order to tune the electrical properties of Co₃O₄, p-type semiconducting Co₃O₄ films were fabricated on the Pb(Mg_1/3Nb_2/3)_0.7Ti_0.3O₃ (PMN-PT), MgAl₂O₄ (MAO), and SrTiO₃ substrates by reactive magnetron sputtering. The Co₃O₄ film on the MAO substrate exhibits perfect epitaxial growth. However, the Co₃O₄ film on the PMN-PT substrate presents dislocation defects between the [011] and [112] orientations. The special ferroelectric domain shape surface and phase transition of the PMN-PT substrate induce the higher concentration of Co vacancies in the Co₃O₄ film, which further reduce the resistivity by several orders of magnitude. The calculated results indicate that introducing Co vacancies can enhance the electrical properties of Co₃O₄ by building impurity levels near the Fermi level, which is beneficial to form free-moving holes in the valence band. The free-moving holes can also be accumulated/dissipated by the ferroelectric field effect of PMN-PT substrates, leading to upward/downward bending of conduction, valence bands, and low/high-resistance states. This work helps us to tune and improve the electrical properties of Co₃O₄.

Resistive Switching Characteristics Improved by Visible-Light Irradiation in a Cs2AgBiBr6-Based Memory Device

Light-modulated lead-free perovskites-based memristors, combining photoresponse and memory, are promising as multifunctional devices. In this work, lead-free double perovskite Cs₂AgBiBr₆ films with dense surfaces and uniform grains were prepared by the low-temperature sol-gel method on indium tin oxide (ITO) substrates. A memory device based on a lead-free double perovskite Cs₂AgBiBr₆ film, Pt/Cs₂AgBiBr₆/ITO/glass, presents obvious bipolar resistive switching behavior. The R_OFF/R_ON ratio under 445 nm wavelength light illumination is ~100 times greater than that in darkness. A long retention capability (>2400 s) and cycle-to-cycle consistency (>500 times) were observed in this device under light illumination. The resistive switching behavior is primarily attributed to the trap-controlled space-charge-limited current mechanism caused by bromine vacancies in the Cs₂AgBiBr₆ medium layer. Light modulates resistive states by regulating the condition of photo-generated carriers and changing the Schottky-like barrier of the Pt/Cs₂AgBiBr₆ interface under bias voltage sweeping.