Coexistence Of Resistive Switching Research Articles

Novel coexistence of resistive switching and ferromagnetism modulation in Ta/La2/3Sr1/3MnO3/Nb:SrTiO3/Ag device

The Ta/La2/3Sr1/3MnO3/Nb:SrTiO3/Ag device has novel coexistence of resistive switching and ferromagnetism modulation. The inactive Ta electrode can effectively balance the Schottky barrier height on both sides of La2/3Sr1/3MnO3, making the current–voltage (I–V) curves of the device exhibit symmetry. The conduction mechanism of the device is conductive filaments of oxygen vacancies at low resistance state (LRS), and Schottky barrier at high resistance state (HRS). The migration of oxygen ions affects not only the resistance but also the ferromagnetism of the device. The suppression of double exchange effect by oxygen vacancies results in higher saturation magnetization (Ms) at HRS than at LRS. Our first-principles calculations are consistent with the experimental results. The stable coexistence of resistive switching and ferromagnetism modulation may provide a possible way to realize multi-state storage.

Improved resistive switching performance and realized electric control of exchange bias in a NiO/HfO2 bilayer structure.

The fluctuation of switching parameters is unavoidable in conductive filaments (CFs)-type resistive switching (RS) devices, which restricts the application in resistive random-access memory. Here, we employed an uninsulated antiferromagnetic (AFM) NiO layer adhered to a well-insulating HfO2 layer to effectively suppress the RS fluctuation by achieving forming-free, narrower set voltage distribution, a more stable on/off ratio, and better endurance in comparison with single-HfO2-layer based RS devices. The conduction scaling behavior indicates that the NiO/HfO2 bilayer has a smaller scale parameter S0 (lateral dimension of the bottleneck for the CFs). Besides this, considering some preexisting conductive paths in the NiO layer, the electric fields and the formation/rupture of CFs can be highly localized, leading to reduced switching fluctuation and improved RS performance in the NiO/HfO2-based RS devices. Moreover, asymmetric I-V curves measured in a high resistance state (HRS) in positively and negatively biased regions and the electric modulation of exchange bias (EB) arising from the Co-NiO interfacial coupling are favorable for revealing the inherent mechanism for RS. The coexistence of RS and EB is also useful to the design of novel multifunctional memory devices.

Low power highly flexible BiFeO3-based resistive random access memory (RRAM) with the coexistence of negative differential resistance (NDR).

We demonstrated the resistive random access memory characteristics for Cu (top contact)/BFO/PMMA (active layer)/ITO (bottom electrode)/PET sheet as a flexible substrate device configuration. The device showed non-volatile bipolar resistive switching characteristics with good repeatability and the coexistence of NDR for 100 cycles or more with 0.28/3.43 mW power consumption for 1st/100th cycles. The device retains its read state for 104 s or more and switches from LRS to HRS or vice versa for 103 cycles with a pulse width of 100 ms for a write-read-erase-read pulse without affecting the memory characteristics. The Weibull distribution suggests that a set state is more stable than the reset state with shape factor β = 25.20. The device follows Ohmic behavior for the lower applied external field and Child square and Schottky emission for the higher external fields. The Joule heating, Sorets, and Fick's forces are responsible for the formation and rupturing of ionic filament. The coexistence of resistive switching and flexible strength of the device sustains the bending curvature of infinity, 0.2 cm, 1 cm, 1.7 cm, and 2.2 cm. The memory characteristics are retained under tensile conditions for 100 cycles or more. More interestingly, the power consumption for sustaining the NDR region with bending (19 μW) is much lower than without bending (0.19 mW). Thus, this study provides the possibility of integrating BFO with flexible substrates suitable for hybrid organic/inorganic memory structures.

Modulation of resistive switching and magnetism of HfOx film by Co doping

The coexistence of resistive switching and magnetism modulation of Co doped HfOx samples with different doping concentrations was reported in this work. The chemical composition, especially oxygen vacancies was analyzed by XPS technology and the influence of Co dopants on resistive switching and magnetism were demonstrated both experimentally and theoretically by first principles calculation. Improved switching performance such as on/off ratio, uniformity and reliability can be obtained by Co doping. In addition, 5.3 % Co doped HfOx sample behaved different magnetism properties in high resistance state and low resistance state (magnetization change of 61.4 %) due to the modulation of defects concentration. The switching behavior and magnetism were both related to the defects in HfOx film. Therefore, the filamentary model consisting of oxygen vacancies and Co ions were proposed to illustrate switching behavior and its relationship with magnetism. Results provide a new idea to clarify the switching mechanism of RRAM, and indicate the promising applications of Co doped HfOx film in the multifunctional electromagnetic devices.

Resistive switching and multiferroic behavior of La0.5Pr0.5FeO3 ferrite thin films

This study examines resistive switching behavior and magnetoelectric coupling in La0.5Pr0.5FeO3 thin films obtained through the polymeric precursor method at a temperature of 500 °C for 2 h. The real and imaginary part of dielectric constant (ε′ and ε″) as a function of temperature demonstrate significant values with increasing temperature and can be caused by the ferroelectric ordering in the present system. The magnetic and dielectric measurements suggest a coupling between magnetic and electric dipoles at room temperature. The magnetization versus temperature curves under zero-field cooling (ZFC) and field cooling (FC) conditions suggest antiferromagnetic to ferromagnetic transition. The maximum magnetoelectric coupling value is ∼0.06 for H ∼1.7 T. By varying the applied electric field, we noted the resistive memory phenomenon from current-voltage (I–V) characteristics being reversibly switched between two stable resistance states. Such behavior can be ascribed to the electron hopping from Fe2+ to Fe3+ levels with oxygen vacancies present in the lattice, as evidenced using XPS analysis. These state-of-art analyses motivated us to study the introduction of praseodymium (Pr) in La3+ sites, considering that LaFeO3 shows paramagnetic behavior at room temperature. La0.5Pr0.5FeO3 thin films exhibited slightly ferromagnetic behavior associated with coupling between cations at the octahedral and tetrahedral sites with the coexistence of resistive switching and magnetoelectric coupling behavior.

P-NiO/n+-Si single heterostructure for one diode-one resistor memory applications

One diode-one resistor (1D1R) memory is one of effective architectures to suppress the crosstalk interference of crossbar network. The conventional 1D1R device usually consists of a stack of sandwich-structure memory and pn junction diode. Herein, we demonstrated a 1D1R device based on a single-stacked p-NiO/n+-Si heterostructure, and its structure and fabrication process are greatly simplified compared with those of multilayer 1D1R devices. Studies on electrical transport properties reveal that the p-type NiO film not only serves as a resistive-switching layer, but also combines with n-type Si to form a pn heterojunction diode. Due to the existence of the built-in electric field, it can neutralize the applied external electric field and the nanoscale conducting filaments (CFs) are only confined to the outside of depletion region of NiO/Si pn junction. Thus, the formation of CFs does not degrade the diode quality, which allows the coexistence of resistive-switching and rectifying behaviors.