Bipolar Resistive Switching Effect in BiFeO_3/Nb:SrTiO_3 Heterostructure by RF Sputtering at Room Temperature

The(001) oriented BiFeO_3 thin film was deposited on the Nb: SrTiO_3 substrate by radio frequency magnetron sputtering technology, and the bipolar resistive switching effect was observed in the BiFeO_3/Nb: SrTiO_3 heterostructure. The results showed that the ratio between the high resistance and low resistance was more than two orders at a reading pulse of-0.5 V and it exhibited excellent retention over 3600 s. The current density-voltage characteristic was dominated by the space-charge-limited conduction. The resistive switching effect of the structure was attributed to the trapping/detrapping of the charge carriers.

Bipolar Resistive Switching in Epitaxial Mn_3O_4 Thin Films on Nb-Doped SrTiO_3 Substrates

Spinel （O01）-orientated Mn304 thin films on Nb-doped SrTi03 （001） substrates are fabricated via the pulsed laser deposition method. X-ray diffraction and high-resolution transmission electron microscopy indicate that the as-prepared epitaxial fihn is well crystaiHzed. In the film plane the orientation relationship between the film and the substrate is [lOOjMn3 04 ｜｜[110] Nb-doped SrTiO3. After an electroforming process, the film shows bipolar nonvolatile resistance switching behavior. The positive voltage bias drives the sample into a low resistance state, while the negative voltage switches it back to a high resistance state. The switching polarity is different from the previous studies. The complex impedance measurement suggests that the resistance switching behavior is of filament type. Due to the performance reproducibility and state stability, Mn3O4 might be a promising candidate for the resistive random access memory devices.

Reversible alternation between bipolar and unipolar resistive switching in La-SrTiO_3 thin films

The alternation from bipolar to unipolar resistive switching is observed in perovskite La0.01Sr0.99TiO3 thin films. These two switching modes can be activated separately depending on the compliance current （Icomp） during the electroforming process： with a higher Icomp （5 mA） the unipolar resistance switching behavior is measured, while the bipolar resistance switching behavior is observed with a lower Icomp （1 mA）. On the basis of I–V characteristics, the switching mechanisms for the URS and BRS modes are considered as being a change in the Schottky-like barrier height and/or width at the Pt/La-SrTiO3 interface and the formation and disruption of conduction filaments, respectively.

Charge transport and bipolar switching mechanism in a Cu/HfO_2/Pt resistive switching cell

Bipolar resistance switching characteristics are investigated in Cu/sputtered-HfO_2/Pt structure in the application of resistive random access memory（RRAM）.The conduction mechanism of the structure is characterized to be SCLC conduction.The dependence of resistances in both high resistance state（HRS） and low resistance state（LRS） on the temperature and device area are studied.Then,the composition and chemical bonding state of Cu and Hf at Cu/HfO_2 interface region are analyzed by x-ray photoelectron spectroscopy（XPS）.Combining the electrical characteristics and the chemical structure at the interface,a model for the resistive switching effect in Cu/HfO_2/Pt stack is proposed.According to this model,the generation and recovery of oxygen vacancies in the HfO_2 film are responsible for the resistance change.

Low Temperature Synthesis of Amorphous La0.7Zn0.3MnO3 Films Grown on p＋-Si Substrates and Its Resistive Switching Properties

Amorphous La0.7Zn0.3MnO3（LZMO） films were deposited on p＋-Si substrates by sol-gel method at low temperature of 450 ℃.The Ag/LZMO/p＋-Si device exhibits invertible bipolar resistive switching and the RHRS/RLRS was about 104-106 at room temperature which can be kept over 103 switching cycles.Better endurance characteristics were observed in the Ag/LZMO/p＋-Si device,the VSet and the VReset almost remained after 103 endurance switching cycles.According to electrical analyses,the conductor mechanism was in low resistor state（LRS） governed by the filament conductor and in the high state（HRS） dominated by the trapscontrolled space-charge-limited current（SCLC） conductor.

Capping CsPbBr3 with ZnO to improve performance and stability of perovskite memristors

The rapid development of information technology has led to an urgent need for devices with fast information storage and processing, a high density, and low energy consumption. Memristors are considered to be next-generation memory devices with all of the aforementioned advantages. Recently, organometallic halide perovskites were reported to be promising active materials for memristors, although they have poor stability and mediocre performance. Herein, we report for the first time the fabrication of stable and high-performance memristors based on inorganic halide perovskite （CsPbBr3, CPB）. The devices have electric field-induced bipolar resistive switching （ReS） and memory behaviors with a large on/off ratio （〉105）, low working voltage （〈1 V） and energy consumption, long data retention （〉104 s）, and high environmental stability, which are achieved via ZnO capping within the devices. Such a design can be adapted to various devices. Additionally, the heterojunction between the CPB and ZnO endows the devices with a light-induced ReS effect of more than 103 with a rapid response speed （〈1 ms）, which enables us to tune the resistance state by changing the light and electric field simultaneously. Such multifunctional devices achieved by the combination of information storage and processing abilities have potential applications for future computing that transcends traditional architectures.

Thickness-dependent monochalcogenide GeSe-based CBRAM for memory and artificial electronic synapses

Investigating the promising chalcogenide materials for the development of memory and advanced neuromorphic computing applications is a critical step in realizing electronic memory and synaptic devices that can efficiently emulate biological synaptic functions.However,the assessment of monochalcogenide materials for the fabrication of highly scalable memory and electronic synaptic devices that can accurately mimic synaptic functions remain limited.In the present study,we investigated the thickness-dependent resistive switching(RS)behavior of conductive bridge random access memory(CBRAM)based on a monochalcogenide GeSe switching medium for its possible application in high-performance memory and electronic synapses.GeSe thin films of different thicknesses(6,13,24,35,47,and 56 nm)were deposited via sputtering to fabricate CBRAM devices with a stacking sequence of Ag/GeSe/Pt/Ti/SiO_(2).The devices exhibited compliance current(CC)-free and electroforming-free RS with highly stable endurance and retention characteristics with no major degradation.All devices with a thickness of 6 nm had a low-resistance state(LRS),which required an initial reset to ensure reliable switching cycles.The devices with a thickness of 47 nm and above exhibited the co-existence of unipolar resistive switching(U-RS)and bipolar resistive switching(B-RS)with the CC-controlled transition between the two switching behaviors.Multilevel resistance states in the 24-nm device between a high-resistance state(HRS)and an LRS were achieved by controlling the set-CC(from 5 mA to CC-free)and the reset stop voltage(from–0.5 to–1.0 V)during the set and reset processes,respectively.The analog RS behavior of the device was further investigated with appropriate pulse measurements to emulate vital synaptic functions,including long-term potentiation(LTP),long-term depression(LTD),spike-rate-dependent plasticity(SRDP),spike-timing-dependent plasticity(STDP),paired-pulse facilitation(PPF),paired-pulse depression(PPD)and post-tetanic potentiation(PTP).Overall,the detailed investigation of thickness-dependent GeSe monochalcogenide material indicates that it is a highly suitable candidate for use in highly scalable memory devices and electronic synapses for neuromorphic computing applications.