Controlled Construction of Atomic Point Contact with 16 Quantized Conductance States in Oxide Resistive Switching Memory

Abstract

A resistive switching device with controlled formation and evolution of conductive filament possesses great capability of being miniaturized to atomic scale for the construction of high-density memory arrays and even in-memory computing architectures. Although the switching mechanism based on ion migration and electrochemistry has been clarified, precise control of the evolution dynamics is still a challenge that hinders the direct application of the memory devices. In this contribution, we propose an effective scanning probe microscope tip-assisted approach for the performance modulation of oxide-based resistive switching devices. The directional migration of oxygen anions inside the hafnium oxide nanofilm is regulated by using the voltage-biased scanning probe microscope (SPM) tip as a microelectrode, so that a single filament would be formed deliberately inside the switching matrix to greatly improve the stability and reliability of the memory device. The variations of the switching parameters, e.g. programming voltages and ON/OFF resistances, have been reduced by at least 33%. More importantly, the elaborate tuning of the filament dimension also gives rise to single atomic point contact in the resistive switching device, producing at least 16 half-integer multiples of quantized conductance states that can be used for multilevel data storage and high-order neuromorphic computing paradigm.

Improving the Recognition Accuracy of Memristive Neural Networks via Homogenized Analog Type Conductance Quantization

“…It can be ascribed to the random ion migration in the polycrystalline metal oxide switching matrix, and consequently the stochastic nature of the branch-shaped multiple conductive filament formation, disruption, and regeneration during cyclic operations [35,36]. In order to achieve a more stable and adjustable conductance state for memristor devices, we performed pre-treatment of the HfO x switching layer using the scanning probe microscope based electrochemical lithography technique [37,38]. By stressing voltages onto the hafnium oxide layer through a conductive SPM tip, the highly localized electric field formed under the tip pinpoint region can induce directional migration of the mobile oxygen vacancies towards the tip position, resulting in loss of the local mass, and therefore formation of a concave structured indentation.…”

“…Conductance quantization can be realized by either controlling the current compliance in the set processes or changing the cut-off voltages of the reset processed [41,42]. Since the positive feedback of the set procedure usually led to uncontrolled overgrowth of the conductive filament with overshooting device conductance, or even the absence of the QC states [37], we employed a relatively more moderate reset process to modulate the evolution of the conductive filament. As depicted in Figure 2c, resetting the Pt/HfO x /Pt device with increasing stopping voltages of −0.6 V to −1.6 V during direct current (DC) scanning can consecutively decrease the device currents.…”

A univariate ternary logic and three-valued multiplier implemented in a nano-columnar crystalline zinc oxide memristor

“…Achieving these targets may require optimization of the compositions of the resistive switching materials, microstructures and AND/OR operating schemes of the devices. [23][24][25] Regarding these concerns, zinc oxide (ZnO) is considered to be a promising candidate for memristors due to its simple stoichiometry, facile fabrication, and good compatibility with the CMOS platform, as well as its tunable resistive switching characteristics via doping and microstructure manipulation. [26][27][28][29][30][31][32] In particular, its columnar crystalline structure with vertical grain boundaries along the direction of growth may provide a cut-through pathway for oxygen anion or oxygen vacancy migration [33][34][35][36] and facilitate the formation of pseudo-straight conductive laments across the switching layer ( Fig.…”

Direct Observation of Structural Deformation Immunity for Understanding Oxygen Plasma Treatment-Enhanced Resistive Switching in HfOx-Based Memristive Devices

“…However, an uncontrolled diameter and number of CFs will cause poor uniformity and reliability of memristive devices. To address this problem, various approaches have been proposed to optimize the RS performance by modulating the growth and rupture of CFs, including device structure design [19,20], operating schemes optimization [21], and materials modulation [22,23].…”