FRBA - Artículos en Revistas
Permanent URI for this collectionhttp://48.217.138.120/handle/20.500.12272/2242
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Item Standards for the Characterization of 2 Endurance in Resistive Switching Devices(2021-10-07) Palumbo, FelixResistive switching (RS) devices are emerging 11 electronic components that could have applications in multiple 12 types of integrated circuits, including electronic memories, true 13 random number generators, radiofrequency switches, neuro- 14 morphic vision sensors, and artificial neural networks. The 15 main factor hindering the massive employment of RS devices in 16 commercial circuits is related to variability and reliability issues, 17 which are usually evaluated through switching endurance tests. 18 However, we note that most studies that claimed high 19 endurances >106 cycles were based on resistance versus cycle 20 plots that contain very few data points (in many cases even 21 <20), and which are collected in only one device. We 22 recommend not to use such a characterization method because 23 it is highly inaccurate and unreliable (i.e., it cannot reliably demonstrate that the device effectively switches in every cycle and 24 it ignores cycle-to-cycle and device-to-device variability). This has created a blurry vision of the real performance of RS devices 25 and in many cases has exaggerated their potential. This article proposes and describes a method for the correct 26 characterization of switching endurance in RS devices; this method aims to construct endurance plots showing one data point 27 per cycle and resistive state and combine data from multiple devices. Adopting this recommended method should result in 28 more reliable literature in the field of RS technologies, which should accelerate their integration in commercial products.Item Temperature of Conductive Nanofilaments in Hexagonal Boron Nitride Based Memristors Showing Threshold Resistive Switching(2021-04-11) Palumbo, FelixTwo-terminal metal/insulator/metal (MIM) memristors exhibiting threshold resistive switching (RS) can develop advanced key tasks in solid-state nano/ micro-electronic circuits, such as selectors and integrate-and-fire electronic neurons. MIM-like memristors using multilayer hexagonal boron nitride (h-BN) as dielectric are especially interesting because they have shown threshold RS with ultra-low energy consumption per state transition down to the zeptojoule regime. However, the factors enabling stable threshold RS at such low operation energies are still not fully understood. Here it is shown that the threshold RS in 150 nm × 150 nm Au/Ag/h-BN/Au memristors is especially stable because the temperature in the h-BN stack during operation (i.e., at low currents ≈1 μA) is very low (i.e., ≈310 K), due to the high in-plane thermal conductivity of h-BN and its low thickness. Only when the device is operated at higher currents (i.e., ≈200 μA) the temperatures at the h-BN increase remarkably (i.e., >500 K), which produce a stable non-volatile conductive nanofilament (CNF). This work can bring new insights to understand the performance of 2D materials based RS devices, and help to develop the integration of 2D materials in high-density nanoelectronicsItem Decoupling the sequence of dielectric breakdown in single device bilayer stacks by radiation-controlled, spatially localized creation of oxide defects(2021-06-14) Palumbo, FelixThe breakdown (BD) sequence in high-K/interfacial layer (HK/IL) stacks for timedependent dielectric breakdown (TDDB) has remained controversial for sub-45 nm CMOS nodes, as many attempts to decode it were not based on proper experimental methods. Knowhow of this sequence is critical to the future design for reliability of FinFETs and nanosheet transistors. We present here the use of radiation fluence as a tool to precisely tune the defect density in the dielectric layer, which jointly with the statistical study of the soft, progressive and hard BD, allow us to infer the BD sequence using a single HfO2-SiOx bilayered MOS structureItem Minimization of the Line Resistance Impact on Memdiode-Based Simulations of Multilayer Perceptron Arrays Applied to Pattern Recognition(2021-02-21) Palumbo, FelixIn this paper, we extend the application of the Quasi-Static Memdiode model to the realistic SPICE simulation of memristor-based single (SLPs) and multilayer perceptrons (MLPs) intended for large dataset pattern recognition. By considering ex-situ training and the classification of the hand-written characters of the MNIST database, we evaluate the degradation of the inference accuracy due to the interconnection resistances for MLPs involving up to three hidden neural layers. Two approaches to reduce the impact of the line resistance are considered and implemented in our simulations, they are the inclusion of an iterative calibration algorithm and the partitioning of the synaptic layers into smaller blocks. The obtained results indicate that MLPs are more sensitive to the line resistance effect than SLPs and that partitioning is the most effective way to minimize the impact of high line resistance valuesItem Analytic circuit model for thermal drying behavior of electronic inks(2023-01-23) Palumbo, FelixUnderstanding the sintering process of conductive inks is a fundamental step in the development of sensors. The intrinsic properties (such as thermal conductivity, resistivity, thermal coefficient, among others) of the printed devices do not correspond to those of the bulk materials. In the field of biosensors porosity plays a predominant role, since it defines the difference between the geometric area of the working electrode and its electrochemical surface area. The analysis reported so far in the literature on the sintering of inks are based on their DC characterization. In this work, the shape and distribution of the nanoparticles that make up the silver ink have been studied employing a transmission electron microscopy. Images of the printed traces have been obtained through a scanning electron microscope at different sintering times, allowing to observe how the material decreases its porosity over time. These structural changes were supported through electrical measurements of the change in the trace impedance as a function of drying time. The resistivity and thermal coefficient of the printed tracks were analyzed and compared with the values of bulk silver. Finally, this work proposes an analytical circuit model of the drying behavior of the ink based on AC characterization at different frequencies. The characterization considers an initial time when the spheric nanoparticles are still surrounded by the capping agent until the conductive trace is obtained. This model can estimate the characteristics that the printed devices would have, whether they are used as biosensors (porous material) or as interconnections (compact material) in printed electronicsItem On the Thermal Models for Resistive Random Access Memory Circuit Simulation(2021-05-11) Palumbo, FelixResistive Random Access Memories (RRAMs) are based on resistive switching (RS) operation and exhibit a set of technological features that make them ideal candidates for applications related to non-volatile memories, neuromorphic computing and hardware cryptography. For the full industrial development of these devices different simulation tools and compact models are needed in order to allow computer-aided design, both at the device and circuit levels. Most of the different RRAM models presented so far in the literature deal with temperature effects since the physical mechanisms behind RS are thermally activated; therefore, an exhaustive description of these effects is essential. As far as we know, no revision papers on thermal models have been published yet; and that is why we deal with this issue here. Using the heat equation as the starting point, we describe the details of its numerical solution for a conventional RRAM structure and, later on, present models of different complexity to integrate thermal effects in complete compact models that account for the kinetics of the chemical reactions behind resistive switching and the current calculation. In particular, we have accounted for different conductive filament geometries, operation regimes, filament lateral heat losses, the use of several temperatures to characterize each conductive filament, among other issues. A 3D numerical solution of the heat equation within a complete RRAM simulator was also taken into account. A general memristor model is also formulated accounting for temperature as one of the state variables to describe electron device operation. In addition, to widen the view from different perspectives, we deal with a thermal model contextualized within the quantum point contact formalism. In this manner, the temperature can be accounted for the description of quantum effects in the RRAM charge transport mechanisms. Finally, the thermometry of conducting filaments and the corresponding models considering different dielectric materials are tackled in depth.