R Rajesh Kumar, Kalaboukhov Alexei, Weng Yi-Chen, Rathod K N, Johansson Ted, Lindblad Andreas, Kamalakar M Venkata, Sarkar Tapati
Division of Solid State Physics, Department of Materials Science and Engineering, Uppsala University, Uppsala SE-751 03, Sweden.
Quantum Device Physics Laboratory, Department of Microtechnology and Nanoscience, Chalmers University of Technology, Göteborg SE-412 96, Sweden.
ACS Appl Mater Interfaces. 2024 Apr 17;16(15):19225-19234. doi: 10.1021/acsami.4c01501. Epub 2024 Apr 5.
Innovations in resistive switching devices constitute a core objective for the development of ultralow-power computing devices. Forming-free resistive switching is a type of resistive switching that eliminates the need for an initial high voltage for the formation of conductive filaments and offers promising opportunities to overcome the limitations of traditional resistive switching devices. Here, we demonstrate mixed charge state oxygen vacancy-engineered electroforming-free resistive switching in NiFeO (NFO) thin films, fabricated as asymmetric Ti/NFO/Pt heterostructures, for the first time. Using pulsed laser deposition in a controlled oxygen atmosphere, we tune the oxygen vacancies together with the cationic valence state in the nickel ferrite phase, with the latter directly affecting the charge state of the oxygen vacancies. The structural integrity and chemical composition of the films are confirmed by X-ray diffraction and hard X-ray photoelectron spectroscopy, respectively. Electrical transport studies reveal that resistive switching characteristics in the films can be significantly altered by tuning the amount and charge state of the oxygen vacancy concentration during the deposition of the films. The resistive switching mechanism is seen to depend upon the migration of both singly and doubly charged oxygen vacancies formed as a result of changes in the nickel valence state and the consequent formation/rupture of conducting filaments in the switching layer. This is supported by the existence of an optimum oxygen vacancy concentration for efficient low-voltage resistive switching, below or above which the switching process is inhibited. Along with the filamentary switching mechanism, the Ti top electrode also enhances the resistive switching performance due to interfacial effects. Time-resolved measurements on the devices display both long- and short-term potentiation in the optimized vacancy-engineered NFO resistive switches, ideal for solid-state synapses achieved in a single system. Our work on correlated oxide forming-free resistive switches holds significant potential for CMOS-compatible low-power, nonvolatile resistive memory and neuromorphic circuits.
电阻式开关器件的创新是超低功耗计算设备发展的核心目标。免形成电阻式开关是一种电阻式开关，它无需用于形成导电细丝的初始高电压，并为克服传统电阻式开关器件的局限性提供了有前景的机会。在此，我们首次展示了在作为不对称Ti/NFO/Pt异质结构制备的NiFeO（NFO）薄膜中，通过混合电荷态氧空位工程实现的免电铸电阻式开关。在可控氧气氛中使用脉冲激光沉积，我们调节了镍铁氧体相中的氧空位以及阳离子价态，后者直接影响氧空位的电荷态。分别通过X射线衍射和硬X射线光电子能谱确认了薄膜的结构完整性和化学成分。电输运研究表明，通过在薄膜沉积过程中调节氧空位浓度的数量和电荷态，可以显著改变薄膜中的电阻式开关特性。电阻式开关机制被认为取决于由于镍价态变化而形成的单电荷和双电荷氧空位的迁移，以及随后在开关层中导电细丝的形成/断裂。这得到了存在有效低压电阻式开关的最佳氧空位浓度的支持，低于或高于该浓度，开关过程会受到抑制。除了丝状开关机制外，Ti顶部电极由于界面效应也增强了电阻式开关性能。对器件的时间分辨测量显示，在优化的空位工程NFO电阻式开关中既有长期增强也有短期增强，这对于在单个系统中实现的固态突触来说是理想的。我们在相关氧化物免形成电阻式开关方面的工作对于CMOS兼容的低功耗、非易失性电阻式存储器和神经形态电路具有巨大潜力。
