This study investigates bipolar and nonpolar resistive-switching of HfO 2 with various metal electrodes. Supported by convincing physical and electrical evidence, it is our contention that the composition of conducting filaments in HfO 2 strongly depends upon the metal electrodes. Nonpolar resistive-switching with the Ni electrode is attributed to the migration of metal cations and the corresponding electrochemical metallization. Conversely, oxygen-deficient filaments induced by anion migration are responsible for bipolar resistive-switching. It was also found that the characteristic nature of the conducting filaments influences many aspects of switching characteristics, including the switching power, cycling variations, and retention at elevated temperatures. V

Reduction in RESET current is crucial for future high-density resistive-switching memory. We have reported a unipolar-switching Ni/ HfO 2 / Si structure with low RESET current of 50 A and RESET power of 30 W. In addition, a unique cycling evolution of RESET current across more than two orders of magnitude allows us to probe into the evolvement of filament morphology at nanoscale, using a simple yet quantitative model. Filament morphology was found to depend strongly on the charge-dissipation current proportional to the powers of SET voltage. Moreover, the formation of inactive semiconductive filaments plays an important role in the reduction in RESET current.

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The implementation of two-dimensional materials into memristor architectures has recently been a new research focus by taking advantage of their atomic thickness, unique lattice, and physical and electronic properties. Among the van der Waals family, Bi 2 O 2 Se is an emerging ternary two-dimensional layered material with ambient stability, suitable band structure, and high conductivity that exhibits high potential for use in electronic applications. In this work, we propose and experimentally demonstrate a Bi 2 O 2 Se-based memristor-aided logic. By carefully tuning the electric field polarity of Bi 2 O 2 Se through a Pd contact, a reconfigurable NAND gate with zero static power consumption is realized. To provide more knowledge on NAND operation, a kinetic Monte Carlo simulation is carried out. Because the NAND gate is a universal logic gate, cascading additional NAND gates can exhibit versatile logic functions. Therefore, the proposed Bi 2 O 2 Se-based MAGIC can be a promising building block for developing next-generation in-memory logic computers with multiple functions.

Effective doping techniques that precisely and locally control the conductivity and carrier polarity, i.e., electron (n-type) or hole (p-type), play a vital role in the remarkable success of Si-based technology and thus are critical for developing useful devices based on two-dimensional layered transition-metal dichalcogenides (TMDs). In contrast to the previous approaches based on either chemical doping or phase transition that requires complex chemicals or a high thermal budget and shows limited tunability and reliability, we propose a simple yet effective electron-beam irradiation (EBI) technique as an alternative for facilitating polarity transformation and transport modulation in selected regions. The EBI process may generate a precise amount of native chalcogen defects in both MoS2 and MoTe2 by controlling the EBI dosage. First-principles simulations support that the presence of native chalcogen vacancies may substantially reduce the band gaps of TMDs. In MoTe2, the progressive evolution of p-type conduction, n-type conduction, to metallic-like conduction can be observed with increasing EBI dosage. The high conductivity of metallic-like MoTe2 induced by EBI is comparable to that in a metallic 1T′-MoTe2, demonstrating the ability to selectively form extremely conductive regions in semiconducting TMDs. The proposed EBI technique could be potentially applied to a wide range of layered TMDs and facilitate the development of high-performance TMD-based devices in the future.