scholarly journals An in-memory computing architecture based on two-dimensional semiconductors for multiply-accumulate operations

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Yin Wang ◽  
Hongwei Tang ◽  
Yufeng Xie ◽  
Xinyu Chen ◽  
Shunli Ma ◽  
...  
Keyword(s):  
Three Dimensional ◽  
High Capacity ◽  
Random Access ◽  
High Energy ◽  
Ex Situ ◽  
Analog Computation ◽  
Electrical Characteristics ◽  
Access Memory ◽  
Multi Level

AbstractIn-memory computing may enable multiply-accumulate (MAC) operations, which are the primary calculations used in artificial intelligence (AI). Performing MAC operations with high capacity in a small area with high energy efficiency remains a challenge. In this work, we propose a circuit architecture that integrates monolayer MoS2 transistors in a two-transistor–one-capacitor (2T-1C) configuration. In this structure, the memory portion is similar to a 1T-1C Dynamic Random Access Memory (DRAM) so that theoretically the cycling endurance and erase/write speed inherit the merits of DRAM. Besides, the ultralow leakage current of the MoS2 transistor enables the storage of multi-level voltages on the capacitor with a long retention time. The electrical characteristics of a single MoS2 transistor also allow analog computation by multiplying the drain voltage by the stored voltage on the capacitor. The sum-of-product is then obtained by converging the currents from multiple 2T-1C units. Based on our experiment results, a neural network is ex-situ trained for image recognition with 90.3% accuracy. In the future, such 2T-1C units can potentially be integrated into three-dimensional (3D) circuits with dense logic and memory layers for low power in-situ training of neural networks in hardware.

Fast and Extensive Intercalation Chemistry in Wadsley-Roth Phase Based High-Capacity Electrodes

2020 ◽  
Author(s):  
Miao Wang ◽  
Zhenpeng Yao ◽  
Qianqian Li ◽  
Yongfeng Hu ◽  
Jing Zhang ◽  
...  
Keyword(s):  
High Capacity ◽  
Lithium Ion ◽  
High Energy ◽  
Ex Situ ◽  
Fast Diffusion ◽  
Fast Kinetics ◽  
Fast Charging ◽  
Depth Study ◽  
Insertion Sites

<p>Wadsley-Roth (W-R) structured oxides featured with wide channels represent one of the most promising material families showing compelling rate performance for lithium ion batteries. But the structural origin for the fast kinetics of W-R structures is not well understood. Herein, we report an in-depth study on the fast and extensive intercalation chemistry of phosphorus stabilized W-R phase PNb<sub>9</sub>O<sub>25 </sub>and its application in high energy and fast-charging devices. We explore the intercalation geometry of PNb<sub>9</sub>O<sub>25</sub> and identify two geometrical types of stable insertion sites with the total amount (2.22 per Nb ion) much higher than conventional intercalation-type electrodes. We reveal the ion transportation kinetics that the Li ions initially diffuse along the open type III channels and then penetrate to type-α edge sites with low kinetic barriers. Through <i>in-situ</i> TEM and <i>ex-situ</i> XRD investigations, we confirm that the whole intercalation/deintercalation process proceeds <i>via</i> a solid-solution behavior with continuous lithium (de)occupying/(re)ordering on the identified insertion sites exhibiting nearly “zero-stress” characteristics. Therefore, the oxide framework of PNb<sub>9</sub>O<sub>25</sub> keeps almost intact with all the fast diffusion channels and insertion cavities well-maintained upon cycling, which accomplishes the unconventional electrochemical performance of<sub> </sub>W-R structured electrodes.</p>

Scanning transmission X-ray microscopy probe forin situmechanism study of graphene-oxide-based resistive random access memory

2013 ◽  
Vol 21 (1) ◽  
pp. 170-176 ◽  
Author(s):  
Hyun Woo Nho ◽  
Jong Yun Kim ◽  
Jian Wang ◽  
Hyun-Joon Shin ◽  
Sung-Yool Choi ◽  
...  
Keyword(s):  
Graphene Oxide ◽  
Random Access ◽  
Random Access Memory ◽  
Resistive Random Access Memory ◽  
Ex Situ ◽  
Access Memory ◽  
Bipolar Resistive Switching ◽  
X Ray ◽  
Scanning Transmission

Here, anin situprobe for scanning transmission X-ray microscopy (STXM) has been developed and applied to the study of the bipolar resistive switching (BRS) mechanism in an Al/graphene oxide (GO)/Al resistive random access memory (RRAM) device. To performin situSTXM studies at the CK- and OK-edges, both the RRAM junctions and theI0junction were fabricated on a single Si3N4membrane to obtain local XANES spectra at these absorption edges with more delicateI0normalization. Using this probe combined with the synchrotron-based STXM technique, it was possible to observe unique chemical changes involved in the BRS process of the Al/GO/Al RRAM device. Reversible oxidation and reduction of GO induced by the externally applied bias voltages were observed at the OK-edge XANES feature located at 538.2 eV, which strongly supported the oxygen ion drift model that was recently proposed fromex situtransmission electron microscope studies.

Fast and Extensive Intercalation Chemistry in Wadsley-Roth Phase Based High-Capacity Electrodes

2020 ◽  
Author(s):  
Miao Wang ◽  
Zhenpeng Yao ◽  
Qianqian Li ◽  
Yongfeng Hu ◽  
Jing Zhang ◽  
...  
Keyword(s):  
High Capacity ◽  
Lithium Ion ◽  
High Energy ◽  
Ex Situ ◽  
Fast Diffusion ◽  
Fast Kinetics ◽  
Fast Charging ◽  
Depth Study ◽  
Insertion Sites

<p>Wadsley-Roth (W-R) structured oxides featured with wide channels represent one of the most promising material families showing compelling rate performance for lithium ion batteries. But the structural origin for the fast kinetics of W-R structures is not well understood. Herein, we report an in-depth study on the fast and extensive intercalation chemistry of phosphorus stabilized W-R phase PNb<sub>9</sub>O<sub>25 </sub>and its application in high energy and fast-charging devices. We explore the intercalation geometry of PNb<sub>9</sub>O<sub>25</sub> and identify two geometrical types of stable insertion sites with the total amount (2.22 per Nb ion) much higher than conventional intercalation-type electrodes. We reveal the ion transportation kinetics that the Li ions initially diffuse along the open type III channels and then penetrate to type-α edge sites with low kinetic barriers. Through <i>in-situ</i> TEM and <i>ex-situ</i> XRD investigations, we confirm that the whole intercalation/deintercalation process proceeds <i>via</i> a solid-solution behavior with continuous lithium (de)occupying/(re)ordering on the identified insertion sites exhibiting nearly “zero-stress” characteristics. Therefore, the oxide framework of PNb<sub>9</sub>O<sub>25</sub> keeps almost intact with all the fast diffusion channels and insertion cavities well-maintained upon cycling, which accomplishes the unconventional electrochemical performance of<sub> </sub>W-R structured electrodes.</p>

Transmission Electron Microscopy of Epitaxial silicides grown by ultra high vacuum deposition

1989 ◽  
Vol 47 ◽  
pp. 462-463
Author(s):  
D. Loretto ◽  
J. M. Gibson ◽  
S. M. Yalisove
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Electron Diffraction ◽  
High Vacuum ◽  
High Energy ◽  
Energy Electron ◽  
Ultra High Vacuum ◽  
Ex Situ ◽  
Transmission Electron

The silicides CoSi2 and NiSi2 are both metallic with the fee flourite structure and lattice constants which are close to silicon (1.2% and 0.6% smaller at room temperature respectively) Consequently epitaxial cobalt and nickel disilicide can be grown on silicon. If these layers are formed by ultra high vacuum (UHV) deposition (also known as molecular beam epitaxy or MBE) their thickness can be controlled to within a few monolayers. Such ultrathin metal/silicon systems have many potential applications: for example electronic devices based on ballistic transport. They also provide a model system to study the properties of heterointerfaces. In this work we will discuss results obtained using in situ and ex situ transmission electron microscopy (TEM).In situ TEM is suited to the study of MBE growth for several reasons. It offers high spatial resolution and the ability to penetrate many monolayers of material. This is in contrast to the techniques which are usually employed for in situ measurements in MBE, for example low energy electron diffraction (LEED) and reflection high energy electron diffraction (RHEED), which are both sensitive to only a few monolayers at the surface.

scholarly journals Synthesis of Si/Fe2O3-Anchored rGO Frameworks as High-Performance Anodes for Li-Ion Batteries

2021 ◽  
Vol 22 (20) ◽  
pp. 11041
Author(s):  
Yajing Yan ◽  
Yanxu Chen ◽  
Yongyan Li ◽  
Xiaoyu Wu ◽  
Chao Jin ◽  
...  
Keyword(s):  
High Performance ◽  
Melt Spinning ◽  
Three Dimensional ◽  
High Capacity ◽  
Reversible Capacity ◽  
High Energy ◽  
High Specific Surface Area ◽  
High Energy Density ◽  
Active Components ◽  
Li Ion

By virtue of the high theoretical capacity of Si, Si-related materials have been developed as promising anode candidates for high-energy-density batteries. During repeated charge/discharge cycling, however, severe volumetric variation induces the pulverization and peeling of active components, causing rapid capacity decay and even development stagnation in high-capacity batteries. In this study, the Si/Fe2O3-anchored rGO framework was prepared by introducing ball milling into a melt spinning and dealloying process. As the Li-ion battery (LIB) anode, it presents a high reversible capacity of 1744.5 mAh g−1 at 200 mA g−1 after 200 cycles and 889.4 mAh g−1 at 5 A g−1 after 500 cycles. The outstanding electrochemical performance is due to the three-dimensional cross-linked porous framework with a high specific surface area, which is helpful to the transmission of ions and electrons. Moreover, with the cooperation of rGO, the volume expansion of Si is effectively alleviated, thus improving cycling stability. The work provides insights for the design and preparation of Si-based materials for high-performance LIB applications.

In Situ Study of Barrier Layers Using Spectroscopic Ellipsometry and Mass Spectroscopy of Recoiled Ions

2000 ◽  
Vol 619 ◽  
Author(s):  
Y. Gao ◽  
A.H. Mueller ◽  
E.A. Irene ◽  
O. Auciello ◽  
A.R. Krauss ◽  
...  
Keyword(s):  
Real Time ◽  
Mass Spectroscopy ◽  
Spectroscopic Ellipsometry ◽  
Nitrogen Concentration ◽  
Random Access ◽  
Copper Interconnects ◽  
Access Memory ◽  
Barrier Layers ◽  
The Stability

ABSTRACTAn in situ study of barrier layers using spectroscopic ellipsometry (SE) and Time-of-Flight (ToF) mass spectroscopy of recoiled ions (MSRI) is presented. First the formation of copper silicides has been observed by real-time SE and in situ MSRI in annealed Cu/Si samples. Second TaSiN films as barrier layers for copper interconnects were investigated. Failure of the TaSiN layers in Cu/TaSiN/Si samples was detected by real-time SE during annealing and confirmed by in situ MSRI. The effect of nitrogen concentration on TaSiN film performance as a barrier was also examined. The stability of both TiN and TaSiN films as barriers for electrodes for dynamic random access memory (DRAM) devices has been studied. It is shown that a combination of in situ SE and MSRI can be used to monitor the evolution of barrier layers and detect the failure of barriers in real-time.

THERMAL EXPANSION OF PHASE-CHANGE RANDOM ACCESS MEMORY CELLS

2008 ◽  
Vol 1072 ◽  
Author(s):  
Jianming Li ◽  
L.P. Shi ◽  
H.X. Yang ◽  
K.G. Lim ◽  
X.S. Miao ◽  
...  
Keyword(s):  
Thermal Stress ◽  
Phase Change ◽  
Electrical Power ◽  
Thermal Strain ◽  
Three Dimensional ◽  
Amorphous State ◽  
Random Access ◽  
Random Access Memory ◽  
Access Memory ◽  
Three Dimensional Finite Element

ABSTRACTThree-dimensional finite element method (FEM) is used to solve the thermal strain-stress fields of phase-change random access memory (PCRAM) cells. Simulation results show that thermal stress concentrates at the interfaces between electrodes and phase change layer and it is significantly larger than that within the phase change layer. It has been found that the peak thermal stress is linearly related to the voltage of electrical pulse in the reset process but once amorphous state is produced in the cell, a nonlinear relationship between thermal stress and electrical power exists. This paper reported the change of thermal stress during set process. It was found that the stress decreases significantly due to the amorphous active region during set processes.

Designed synthesis of ultrafine NiO nanocrystals bonded on a three dimensional graphene framework for high-capacity lithium-ion batteries

2018 ◽  
Vol 42 (12) ◽  
pp. 9901-9910 ◽  
Author(s):  
Jiayuan Chen ◽  
Xiaofeng Wu ◽  
Qiangqiang Tan ◽  
Yunfa Chen
Keyword(s):  
Lithium Ion Batteries ◽  
Three Dimensional ◽  
High Capacity ◽  
Lithium Ion ◽  
Nio Nanocrystals ◽  
Designed Synthesis

NiO nanocrystals/3D-GF nanohybrids are fabricated in situ and used for high-capacity lithium-ion batteries.

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