本文首次展示基于$\ m Al_2O_3-TiO_2$导电氧化物界面的价变阻变器件，该界面兼作背电极和氧空位储库，采用CMOS兼容工艺，为器件调谐和选择提供新设计空间。
摘要：
阻变存储器预示着一种变革性的存储与计算技术，在性能和能效方面具有显著优势。在此，我们采用一种简单且可扩展的导电氧化物界面材料体系，并利用其独特性质构建了一种新型阻变器件。我们首次展示了基于$\ m Al_2O_3-TiO_2$的价变阻变器件，其中导电氧化物界面既充当背电极，又充当开关所需的缺陷储库。非晶-多晶$\ m Al_2O_3-TiO_2$导电界面是通过简化二维电子气（2DEGs）制备工艺的技术路径获得的，使其更适用于实际的大规模集成。我们将器件化学和微观结构的物理分析与开关行为和性能的综合电学分析相结合。我们将阻变现象的起源定位到导电氧化物界面，该界面作为底电极和氧空位储库。后者在价变阻变器件中起着关键作用。这种基于可扩展且与互补金属氧化物半导体（CMOS）技术兼容的制造工艺的新型器件，为增强可调谐性和简化器件选择难题开辟了新的设计空间。
英文摘要：
Resistive switching devices herald a transformative technology for memory and computation, offering considerable advantages in performance and energy efficiency. Here we employ a simple and scalable material system of conductive oxide interfaces and leverage their unique properties for a new type of resistive switching device. For the first time, we demonstrate an $\rm Al_2O_3-TiO_2$ based valence-change resistive switching device, where the conductive oxide interface serves both as the back electrode and as a reservoir of defects for switching. The amorphous-polycrystalline $\rm Al_2O_3-TiO_2$ conductive interface is obtained following the technological path of simplifying the fabrication of the two-dimensional electron gases (2DEGs), making them more scalable for practical mass integration. We combine physical analysis of the device chemistry and microstructure with comprehensive electrical analysis of its switching behavior and performance. We pinpoint the origin of the resistive switching to the conductive oxide interface, which serves as the bottom electrode and as a reservoir of oxygen vacancies. The latter plays a key role in valence-change resistive switching devices. The new device, based on scalable and complementary metal-oxide-semiconductor (CMOS) technology-compatible fabrication processes, opens new design spaces towards increased tunability and simplification of the device selection challenge.
This study demonstrates multilevel switching at 1.5 K of Al2O3/TiO2-x resistive memory devices fabricated with CMOS-compatible processes and materials. The I-V characteristics exhibit a negative differential resistance (NDR) effect due to a Joule-heating-induced metal-insulator transition of the Ti4O7 conductive filament. Carrier transport analysis of all multilevel switching I-V curves show that while the insulating regime follows the space charge limited current (SCLC) model for all resistance states, the conduction in the metallic regime is dominated by SCLC and trap-assisted tunneling (TAT…
In this work, we investigate the behavior of Al2O3/TiO2-x cross-point memristors in cryogenic environment. We report successful resistive switching of memristor devices from 300 K down to 1.5 K. The I-V curves exhibit negative differential resistance effects between 130 and 1.5 K, attributed to a metal-insulator transition (MIT) of the Ti4O7 conductive filament. The resulting highly nonlinear behavior is associated to a maximum ION/IOFF ratio of 84 at 1.5 K, paving the way to selector-free cryogenic passive crossbars. Finally, temperature-dependant thermal activation energies related to the co…
Resistive switching devices are promising emerging non-volatile memories. However, one of the biggest challenges for resistive switching (RS) memory applications is the device-to-device (D2D) variability which is related to the intrinsic stochastic formation and configuration of oxygen vacancy (VO) conductive filaments. In order to reduce D2D variability, the control of oxygen vacancy formation and configuration is paramount. We report in this study Zr doping of TaOx-based RS devices prepared by pulsed laser deposition (PLD) as an efficient mean to reduce VO formation energy and increase condu…
Resistive switching devices based on transition metal oxides require formation of a conductive filament in order for the device to be able to switch. Such filaments have been proposed to form by the reduction of the oxide due to application of the electric field, but this report seeks to rebut that interpretation. Frequently reported physical changes during electro-formation include delamination of electrodes, crystallization of functional oxide, intermixing of electrode and oxide materials, and extensive loss of oxygen presumably to the ambient. Here we show that most of these effects are not…
An electro-thermal computational study of conducting channels in dielectric thin films using self-consistent phase-field methodology: A view toward the physical origins of resistive switching
Memristors are among the most promising elements for modern microelectronics, having unique properties such as quasi-continuous change of conductance and long-term storage of resistive states. However, identifying the physical mechanisms of resistive switching and evolution of conductive filaments in such structures still remains a major challenge. In this work, aiming at a better understanding of these phenomena, we experimentally investigate an unusual effect of enhanced conductive filament stability in memristors with copper filaments under the applied voltage and present a simplified theor…
The operation of resistive and phase-change memory (RRAM and PCM) is controlled by highly localized self-heating effects, yet detailed studies of their temperature are rare due to challenges of nanoscale thermometry. Here we show that the combination of Raman thermometry and scanning thermal microscopy (SThM) can enable such measurements with high spatial resolution. We report temperature-dependent Raman spectra of HfO$_2$, TiO$_2$ and Ge$_2$Sb$_2$Te$_5$ (GST) films, and demonstrate direct measurements of temperature profiles in lateral PCM devices. Our measurements reveal that electrical and …
In this work, we propose a novel integration in order to significantly reduce the High Resistance State vari-ability and to improve thermal stability in Oxide-based Resistive Random Access Memory (OxRRAM) devices. A novel device featuring a metallic liner, acting as a parallel resistance, is presented. To assess the effect of this solution, we compare the results with a standard OxRRAM cell structure. A very good stability of the resistive states, both in endurance and temperature, is highlighted and explained thanks to a conductive fila-ment based model.
Self-ordered nanotubular titania TiO2-NT with outer tube diameter of 45 nm are synthesized using the anodic oxidation of titanium foil. Four sets of memristors with 100 $μm$ diameter based on Ti/TiO2-NT/Au sandwich structures with an oxide layer thickness of 80, 120, 160 and 200 nm are fabricated. Current-voltage (CV) characteristics for the obtained samples in the static and dynamic operation modes are studied. Resistance in high and low resistance states is estimated. Basing on the analysis of the CV characteristics in dynamic mode (> 14 000 switchings) a prospective of use for synthesized T…
Oxide-based Random Access Memory (OxRAM), is part of the larger family of Resistive RAM (RRAM) memories. Generally OxRAM cells consist of a transition metal oxide (typically HfO2, Ta2O5, TiO2) sandwiched between two metal electrodes (typically TiN, TaN, W but also Pt, Ir). This thesis describes the experimental investigation performed on OxRAM memories during a 6-months internship project at imec research institute (Leuven, Belgium). From previous studies, HfO-based OxRAM memories showed good endurance properties (with more than 10e9 write cycles), low operating current (as low as 10 uA), and …
Thin (approximately 10 nm) oxide buffer layers grown over lead-halide perovskite device stacks are critical for protecting the perovskite against mechanical and environmental damage. However, the limited perovskite stability restricts the processing methods and temperatures (<=110 C) that can be used to deposit the oxide overlayers, with the latter limiting the electronic properties of the oxides achievable. In this work, we demonstrate an alternative to existing methods that can grow pinhole-free TiOx (x = 2.00+/-0.05) films with the requisite thickness in <1 min without vacuum. This techniqu…
