scholarly journals Self-Rectifying Resistive Switching and Short-Term Memory Characteristics in Pt/HfO2/TaOx/TiN Artificial Synaptic Device

Nanomaterials ◽  
2020 ◽  
Vol 10 (11) ◽  
pp. 2159 ◽  
Author(s):  
Hojeong Ryu ◽  
Sungjun Kim
Keyword(s):  
Resistive Switching ◽  
Short Term Memory ◽  
Atomic Layer ◽  
The Self ◽  
Short Term ◽  
Paired Pulse ◽  
Interval Time ◽  
Layer Deposition ◽  
Switching Characteristics ◽  
Reset Pulse

Here, we propose a Pt/HfO2/TaOx/TiN artificial synaptic device that is an excellent candidate for artificial synapses. First, XPS analysis is conducted to provide the dielectric (HfO2/TaOx/TiN) information deposited by DC sputtering and atomic layer deposition (ALD). The self-rectifying resistive switching characteristics are achieved by the asymmetric device stack, which is an advantage of the current suppression in the crossbar array structure. The results show that the programmed data are lost over time and that the decay rate, which is verified from the retention test, can be adjusted by controlling the compliance current (CC). Based on these properties, we emulate bio-synaptic characteristics, such as short-term plasticity (STP), long-term plasticity (LTP), and paired-pulse facilitation (PPF), in the self-rectifying I–V characteristics of the Pt/HfO2/TaOx/TiN bilayer memristor device. The PPF characteristics are mimicked by replacing the bio-stimulation with the interval time of paired pulse inputs. The typical potentiation and depression are also implemented by optimizing the set and reset pulse. Finally, we demonstrate the natural depression by varying the interval time between pulse inputs.

scholarly journals Understanding the Resistive Switching Phenomena of Stacked Al/Al2O3/Al Thin Films from the Dynamics of Conductive Filaments

Complexity ◽  
2017 ◽  
Vol 2017 ◽  
pp. 1-10 ◽  
Author(s):  
Joel Molina-Reyes ◽  
Luis Hernandez-Martinez
Keyword(s):  
Resistive Switching ◽  
Atomic Layer ◽  
Memory Device ◽  
Switching Behavior ◽  
Processing Temperature ◽  
Force Microscopy ◽  
Atomic Force ◽  
Layer Deposition ◽  
Metal Insulator Metal ◽  
Switching Characteristics

We present the resistive switching characteristics of Metal-Insulator-Metal (MIM) devices based on amorphous Al2O3 which is deposited by Atomic Layer Deposition (ALD). A maximum processing temperature for this memory device is 300°C, making it ideal for Back-End-of-Line (BEOL) processing. Although some variations in the forming, set, and reset voltages (VFORM, VSET, and VRESET) are obtained for many of the measured MIM devices (mainly due to roughness variations of the MIM interfaces as observed after atomic-force microscopy analysis), the memristor effect has been obtained after cyclic I-V measurements. These resistive transitions in the metal oxide occur for both bipolar and unipolar conditions, while the IOFF/ION ratio is around 4–6 orders of magnitude and is formed at gate voltages of Vg<4 V. In unipolar mode, a gradual reduction in VSET is observed and is related to combined (a) incomplete dissolution of conductive filaments (made of oxygen vacancies and metal ions) which leaves some residuals and (b) thickening of chemically reduced Al2O3 during localized Joule heating. This is important because, by analyzing the macroscopic resistive switching behavior of this MIM structure, we could indirectly relate it to microscopic and/or nanoscopic phenomena responsible for the physical mechanism upon which most of these devices operate.

scholarly journals Volatile Resistive Switching Characteristics of Pt/HfO2/TaOx/TiN Short-Term Memory Device

Metals ◽  
2021 ◽  
Vol 11 (8) ◽  
pp. 1207
Author(s):  
Hojeong Ryu ◽  
Sungjun Kim
Keyword(s):  
Resistive Switching ◽  
Short Term Memory ◽  
Memory Device ◽  
Short Term ◽  
Term Memory ◽  
Transmission Electron ◽  
Natural Decrease ◽  
Neuromorphic System ◽  
Switching Characteristics ◽  
Memory Applications

In this work, we study the threshold switching and short-term memory plasticity of a Pt/HfO2/TaOx/TiN resistive memory device for a neuromorphic system. First, we verify the thickness and elemental characterization of the device stack through transmission electron microscopy (TEM) and an energy-dispersive X-ray spectroscopy (EDS) line scan. Volatile resistive switching with low compliance current is observed under the DC sweep in a positive bias. Uniform cell-to-cell and cycle-to-cycle DC I-V curves are achieved by means of a repetitive sweep. The mechanism of volatile switching is explained by the temporal generation of traps. Next, we initiate the accumulation of the conductance and a natural decrease in the current by controlling the interval time of the pulses. Finally, we conduct a neuromorphic simulation to calculate the pattern recognition accuracy. These results can be applicable to short-term memory applications such as temporal learning in a neuromorphic system.

Resistive Switching Characteristics of Atomic-Layer-Deposited Y2O3 Insulators with Deposition Temperature

2015 ◽  
Vol 15 (10) ◽  
pp. 7586-7589 ◽  
Author(s):  
Yong Chan Jung ◽  
Sejong Seong ◽  
Taehoon Lee ◽  
In-Sung Park ◽  
Jinho Ahn
Keyword(s):  
Resistive Switching ◽  
Growth Temperature ◽  
Film Growth ◽  
Atomic Layer ◽  
High Resistance State ◽  
Insulating Films ◽  
Layer Deposition ◽  
Resistance State ◽  
Switching Characteristics ◽  
Unipolar Resistive Switching

Resistive switching characteristics of insulating Y2O3 films grown by an atomic layer deposition technique have been investigated with their growth temperature range of 250 °C to 350 °C. Ru/Y2O3/Ru resistors reveal the bi-stable unipolar resistive switching behaviors. Resistive switching behaviors are related to the chemical bonding states of Y2O3 insulating films. As the insulating film growth temperature increases, Y2O3 film becomes much stoichiometric and little contaminated with impurities. Moreover, the resistance ratio high resistance state to low resistance state increases at growth temperature over 300 °C.

Resistive Switching Characteristics in TiO2 ReRAM with Top Electrode of Co Selectively Formed on SAMs Printed Patterns

2007 ◽  
Vol 124-126 ◽  
pp. 603-606
Author(s):  
Sang Hee Won ◽  
Seung Hee Go ◽  
Jae Gab Lee
Keyword(s):  
Resistive Switching ◽  
Random Access ◽  
Atomic Layer ◽  
High Resistance State ◽  
Resistive Random Access Memory ◽  
Tio2 Thin Films ◽  
Selective Deposition ◽  
Precise Control ◽  
Resistance State ◽  
Switching Characteristics

Simple process for the fabrication of Co/TiO2/Pt resistive random access memory, called ReRAM, has been developed by selective deposition of Co on micro-contact printed (μ-CP) self assembled monolayers (SAMs) patterns. Atomic Layer Deposition (ALD) was used to deposit TiO2 thin films, showing its ability of precise control over the thickness of TiO2, which is crucial to obtain proper resistive switching properties of TiO2 ReRAM. The fabrication process for Co/TiO2/Pt ReRAM involves the ALD of TiO2 on sputter-deposited Pt bottom electrode, followed by μ-CP with SAMs and then selective deposition of Co. This results in the Co/TiO2/Pt structure ReRAM. For comparison, Pt/TiO2/Pt ReRAM was produced and revealing the similar switching characteristics as that of Co/TiO2/Pt, thus indicating the feasibility of Co replacement with Pt top electrode. The ratios between the high-resistance state (Off state) and the low-resistance state (On state) were larger than 102. Consequently, the selective deposition of Co with μ-CP, newly developed in this study, can simplify the process and thus implemented into the fabrication of ReRAM.

scholarly journals Study on the Preferred Application-Oriented Index for Mental Fatigue Detection

2018 ◽  
Vol 15 (11) ◽  
pp. 2555 ◽  
Author(s):  
Tianhong Duan ◽  
Nong Zhang ◽  
Kaiway Li ◽  
Xuelin Hou ◽  
Jun Pei
Keyword(s):  
Short Term Memory ◽  
Fatigue Testing ◽  
Mental Fatigue ◽  
The Self ◽  
Short Term ◽  
Flicker Fusion Frequency ◽  
Term Memory ◽  
Severe Fatigue ◽  
Speed Perception ◽  
Fatigue Detection

Most of the research on mental fatigue evaluation has mainly concentrated on some indexes that require sophisticated and large instruments that make the detection of mental fatigue cumbersome, time-consuming, and difficult to apply on a large scale. A quick and sensitive mental fatigue detection index is necessary so that mentally fatigued workers can be alerted in time and take corresponding countermeasures. However, to date, no studies have compared the sensitivity of common objective evaluation indexes. To solve these problems, this study recruited 56 human subjects. These subjects were evaluated using six fatigue indexes: the Stanford sleepiness scale, digital span, digital decoding, short-term memory, critical flicker fusion frequency (CFF), and speed perception deviation. The results of the fatigue tests before and after mental fatigue were compared, and a one-way analysis of variance (ANOVA) was performed on the speed perception deviation. The results indicated the significance of this index. Considering individual differences, the relative fatigue index (RFI) was proposed to compare the sensitivity of the indexes. The results showed that when the self-rated fatigue grade changed from non-fatigue to mild fatigue, the ranges of RFI values for digital span, digital decoding, short-term memory, and CFF were 0.175–0.258, 0.194–0.316, 0.068–0.139, and 0.055–0.075, respectively. Correspondingly, when the self-rated fatigue grade changed to severe fatigue, the ranges of RFI values for the above indexes were 0.415–0.577, 0.482–0.669, 0.329–0.396, and 0.114–0.218, respectively. These results suggest that the sensitivity of the digital decoding, digital span, short-term memory, and CFF decreased sequentially when the self-evaluated fatigue grade changed from no fatigue to mild or severe fatigue. The RFI individuality of the speed perception deviation is highly variable and is not suitable as an evaluation index. In mental fatigue testing, digital decoding testing can provide faster, more convenient, and more accurate results.

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