Electric field control of resistive switching and magnetization in epitaxial LaBaCo2O5+δ thin films.

The low operating temperature and volatile characteristics of the magnetization change are the main obstacles for the practical applications of spintronic and magnetic memories. In this work, both the resistive switching and magnetization switching are realized in Pt/LaBaCo2O5+δ (LBCO)/Nb-doped SrTiO3 (Nb-STO) devices at room temperature through an electric field. Unlike the traditional approach of an external stress inducing a volatile magnetization change, the magnetization in the Pt/LBCO/Nb-STO device is modulated by an electrical field, along with the resistive switching. The resistive and magnetization switching can be attributed to the variation of the depletion layer width at the LBCO/Nb-STO interface via oxygen vacancy migration and the increase/decrease of the Co-O-Co bond length, respectively. The present device with the synchronous manipulation of both resistance and magnetization at room temperature can be applied in nonvolatile resistive memories and novel magnetic multifunctional devices.

Structure and magnetic properties of highly oriented LaBaCo2O5+δ films deposited on Si wafers with Pt/Ti buffer layer.

Fabrication of highly crystalline oxide films onto silicon wafers has long been a critical obstacle for integrating multi-functional oxides into silicon-based technology. Herein, Pt/Ti is used as a buffer layer for the integration of highly oriented crystalline LaBaCo2O5+δ (LBCO) thin films onto silicon via pulsed laser deposition. LBCO films are highly (00l) oriented with smooth and sharp LBCO/Pt interfaces. The highly oriented LBCO films exhibit a high magnetic transition temperature (TC) and large coercive field (HC) with superparamagnetism over those deposited on single crystal substrates. What is more, the metallic-like behavior with enhanced magnetoresistance is also observed. The opportunity of using a Pt/Ti buffer layer as the growth template opens an alternative route for integrating functional transition metal oxides with tunable magnetic properties into Si-based technology.

Multi-gate memristive synapses realized with the lateral heterostructure of 2D WSe2 and WO3.

The development of novel synaptic device architectures with a high order of synaptic plasticity can provide a breakthrough toward neuromorphic computing. Herein, through the thermal oxidation of two-dimensional (2D) WSe2, unique memristive synapses based on the lateral heterostructure of 2D WSe2 and WO3, with multi-gate modulation characteristics, are firstly demonstrated. An intermediate transition layer in the heterostructure is observed through transmission electron microscopy. Raman spectroscopy and detailed electrical measurements provide insights into the mechanism of memristive behavior, revealing that the protons injected into/removed from the intermediate transition layer account for the memristive behavior. This novel memristive synapse can be used to emulate two neuron-based synaptic functions, like post-synaptic current, short-term plasticity and long-term plasticity, with remarkable linearity, symmetry, and an ultralow energy consumption of ∼2.7 pJ per spike. More importantly, the synaptic plasticity between the drain and source electrodes can be effectively modulated by the gate voltage and visible light in a four-terminal configuration. Such multi-gate tuning of the synaptic plasticity cannot be accomplished by any previously reported multi-gate synaptic devices that only mimic two neuron-based synapses. This new synaptic architecture with electrical and optical modulation enables a realistic emulation of biological synapses whose synaptic plasticity can be additionally regulated by the surrounding astrocytes, greatly improving the recognition accuracy and processing capacity of artificial neuristors, and paving a new way for highly efficient neuromorphic computation devices.