bluuebunny/crossref_metadata_2025_split huggingface dataset:
Critical Safety Boundaries of Lithium Electrodeposition Against Nanoporous Ceramic Separators
Authors: Bai Peng 
Published: February 2020

The growth mechanisms and morphology of lithium electrodeposits in liquid electrolyte are highly current-dependent [1]. While it was reported that diffusion-limited dendritic growths can easily penetrate, and reaction-limited whisker growths can be blocked by ceramic nanopores [2], the current densities that lead to the unsafe dendritic growths and safe whisker growths are disparate from each other. The penetration of lithium metal through nanopores can still occur at intermediate, yet under-limiting current densities [3]. In this study, operando experiments on transparent capillary cells and post-mortem analyses on realistic sandwich cells were performed to obtain insights on the safety-related growth mechanisms across a wide range of practical current densities. Our results suggest the existence of three growth modes of lithium, due to the competing reactions of lithium deposition and the solid electrolyte interphase (SEI) formation. A critical current density (6 mA cm-2), roughly 30% of the system-specific limiting current density, is identified as a practical safety boundary for battery design and operation, under which root growing lithium whiskers are the dominant structure of electrodeposition and can be blocked by commercial nanoporous ceramic separators. Our operando experiments of miniature junction cells also reveal that metal penetration of the separator does not lead to zero voltage immediately, but rather to sudden, small voltage drops, which should not be treated as benign soft shorts.

References

[1] W. Xu, J. Wang, F. Ding, X. Chen, E. Nasybulin, Y. Zhang and J.-G. Zhang, Energy Environ. Sci., 2014, 7, 513–537
[2] P. Bai, J. Li, F. R. Brushett and M. Z. Bazant, Energy Environ. Sci., 2016, 9, 3221-3229
[3] P. Bai, J. Guo, M. Wang, A. Kushima, L. Su, J. Li, F. R. Brushett, M. Z. Bazant, Joule, 2018, 2, 2434-2449
(Invited) Equivalent Circuit Modeling for EIS on Structured Electrode in LIB
Authors: Osaka Tetsuya , Nara Hiroki 
Published: February 2020

For realization of energy sustainable society, electric energy storages are essential to efficiently use energies generated by solar- and wind- power plants and to displace petrol-driven vehicles to electric-powered vehicles. Lithium-ion battery (LIB) is one of the promising electric energy storages because of high-power and high-energy density. For further improvement of LIBs on high-power and high-energy density, a structure of electrodes is important. Because there is a trade-off relationship between power-density and energy-density, which relates to electrode density. The electrode structure will change with degradation due to charge-discharge cycles. Therefore, non-destructive diagnosis is required for evaluation of the electrode structure. Electrochemical impedance spectroscopy (EIS) is powerful to analyze electrodes without disassembling the battery. However, the evaluation of the structural change of electrode is required to model a proper equivalent circuit. In this presentation, a case of an intricate electrode which has reaction distribution in depth direction and a case of an intricate electrode which has particle size distribution will be introduced. For modeling the reaction distribution in depth direction, transmission line model (TLM) is applied (shown in Fig. (a)). [1–3] For modeling the particle size distribution, a parallel circuit of R
ct­­–W (charge transfer resistance and Warburg impedance) is applied to model various particle size groups (shown in Fig. (b)). [4] In the model, diffusion length in solid is assumed to be various. Additionally, to verify the equivalent circuit, a case with different particle size distribution (Fig. (c)) was evaluated.
References
[1] H. Nara, D. Mukoyama, T. Yokoshima, T. Momma, T. Osaka, Impedance Analysis with Transmission Line Model for Reaction Distribution in a Pouch Type Lithium-Ion Battery by Using Micro Reference Electrode, J. Electrochem. Soc. 163 (2016) A434–A441. doi:10.1149/2.0341603jes.
[2] H. Nara, S. Tominaka, T. Momma, T. Osaka, Impedance Analysis Counting Reaction Distribution on Degradation of Cathode Catalyst Layer in PEFCs, J. Electrochem. Soc. 158 (2011) B1184. doi:10.1149/1.3610988.
[3] H. Nara, T. Momma, T. Osaka, Impedance analysis of the effect of flooding in the cathode catalyst layer of the polymer electrolyte fuel cell, Electrochim. Acta. 113 (2013) 720–729. doi:10.1016/j.electacta.2013.06.055.
[4] H. Nara, K. Morita, D. Mukoyama, T. Yokoshima, T. Momma, T. Osaka, Impedance Analysis of LiNi1/3Mn1/3Co1/3O2 Cathodes with Different Secondary-particle Size Distribution in Lithium-ion Battery, Electrochim. Acta. 241 (2017). doi:10.1016/j.electacta.2017.04.153.

Figure 1
Study on Forming-Free Characteristic of Amorphous Carbon Oxide Reram By Controlling Cu-Filament Shape
Authors: Jin Soo-Min , Kwon Ki-Hyun , Kim Dong-Won , Kim Hea-Jee , Yang Hun-Mo , Kim Ji-Yeon , Park Jea-Gun 
Published: February 2020

Resistive random access memory (ReRAM) is one of the most promising candidates for the next-generation memory due to its simple structure, high switching speed and low power consumption [1]. Recently, there has been large interests in using carbon-baed material as solid electrolyte to overcome the limit of conventional metal-oxide memory. It has remarkable advantages over past metal-oxide memory such as high memory margin (Ion/Ioff
> 100) and fast switching speed (20~50ns) [2]. However, the requirement of forming process to activate resisitive switching operation is one of the critical issues. Forming process may degrade the device switching characteristic and is not desirable for circuit design. In this study, forming-free characteristic of a-COx (amorphous carbon oxide) based ReRAM was observed by controlling the Cu-filament shape. To accurately control the Cu-atom concentration profile, insertion of Cu thin film was carried out in several ways. The first device, named A, was fabricated with the common ReRAM structure of Pt / Cu-doped a-COx / W. The second device, named B, was vertically stacked with the strcutrue of Pt / a-COx / Cu-doped a-COx / W. The third device, named C, was vertically stacked with the strcutrue of Pt / Cu-doped a-COx / a-COx / Cu-doped a-COx / W. The device was fabricated on W bottom electrode wafer patterned from 34 nm to 1921 nm by photo lithography process. The a-COx and other metals were deposited using dc magnetron sputter (PVD method). After the fabrication, the Cu-atom concentration profile was carefully examined using SIMS analysis to understand the correlation between forming-free chracteristic and Cu-filament shape. Forming-free characteristic device presented identical forming and set voltage of -0.85 V. Moreover, the result indicated that the high resistance state current of 2.41-7 A at 0.1 V, low resistance state current of 5.98-5 A at 0.1 V and the memory window margin (Ion/Ioff) of 2.48×102. In our study, we present that the precise design of the Cu-atom concentration profile of a-COx based ReRAM is the significant key to achieve the forming-free and stable non-volatile memory characteristic.
[1] Daniele Ielmini, Semicond. Sci. Technol. 31 (2016) 063002
[2] Claudia A. Santini et al, NAT COMMUN, 6:8600 (2015)

* This material is based upon work supported by the Ministry of Trade, Industry & Energy(MOTIE, Korea) under Industrial Technology Innovation Program (10068055).

Figure 1
Multilevel Resistive Switching in Hf-Based Rram
Authors: Jain Barsha , Huang Chia-sheng , Misra Durgamadhab , Tapily Kandabara , Clark Robert D. , Consiglio Steven , Wajda Cory S. , Leusink Gert J. 
Published: February 2020

Resistive random-access memory (RRAM) device has attracted wide attention for next-generation nonvolatile memory (NVM) application due to simple structure, high cycling endurance, good retention, low power consumption and fast switching time (1, 2). In recent years, RRAM devices are extensively researched for multi-level data storage (3, 4). RRAM devices can be driven to various resistance states by applying suitable compliance current values during the switching operation.
In this work, multilevel resistive switching behaviors of RRAM devices with three different dielectric materials like HfO2, HfAlO2 and HfZrO2 are investigated with fixed top/bottom electrodes. To control the resistance state, a thin Al2O3 layer (1 nm) was inserted between the bottom electrode and switching dielectric (Ti/TiN/Al2O3/HfAlO2 or HfZrO2 or HfO2/Ti/TiN). The fabrication details of these devices are presented elasewhere (5). Fig. 1 shows DC endurance cycling on the LRS/HRS resistances of the three RRAM structures, (a) HfAlO2, (b) HfZrO2 and (c) HfO2 for different increasing compliance currents. The endurance cycling is performed with 20 cycles per compliance level. As can be seen from the figure, different low resistance states (LRS) and high resistance states (HRS) are well resolved after dc endurance cycling for HfAlO2 and HfZrO2 based RRAM devices. Devices with HfO2, on the other hand, does not show any multilevel LRS or HRS behavior for increase in compliance current. The reason is possibly due to the lack of oxygen vacancies available in the HfO2-RRAM structure.
When HfZrO2 was subjected to a post deposition annealing (PDA) in nitrogen environment, the resistance distribution of LRS and HRS was improved, possibly due to improvement of dielectric quality while the oxygen vacancy concentration remained the same. To further improve the resistance window an additional 2 nm thick TiN layer was added before the Ti layer on top electrode of HfZrO2 based RRAM. The cycle to cycle distribution of HRS/LRS resistance of HfZrO2 based RRAM was significantly improved while the compliance current for switching was increased.
In summary, process optimization and electrode selection with HfZrO2 as the switching layer can provide significant multilevel storage in RRAM devices.

References:

E. Ambrosi, A. Bricalli, M. Laudato and D. Ielmini, Faraday discussions DOI: 10.1039/c8fd00106e (2018).

A. Prakash and H. Hwang. Physical Sciences Reviews, vol. 1(6), (2016)

Chen, et al., Semiconductor Science and Technology7 (2015): 075002.

J. Jang and V. Subramanian. Thin Solid Films 625 (2017): 87-92.

D. Misra, S. Sultana, B. Jain, N. Bhat, K. Tapily, R.D. Clark, S. Consiglio, C.S. Wajda, and G.J. Leusink, ECS Trans., vol. 86(2), 77, 2018.

Figure 1
Perpendicular Spin-Transfer-Torque Magnetic Tunnel Junction Multi-Level Cell with Dual Free Layers and MgO Tunnel Barriers
Authors: Baek Jong Ung , Jun Han-Sol , Choi Jin-Young , Kondo Kei , Park Jea-Gun 
Published: February 2020

Perpendicular spin-transfer-torque magnetic random access memory (p-STT-MRAM) is a promising candidate memory device for replacing dynamic random access memory (DRAM) facing with 10-nm sub scaling down. In addition to scaling down, p-STT MRAM has many advantages like fast write/read speed (~10ns) as DRAM, low power consumption (<1pJ), high endurance (>1014), and non-volatility (retention time > 10 years). But to replace DRAM, there are several challenges to be solved. First, high tunneling magneto-resistance (TMR) ratio for read sensing margin. Second, low critical current density(J
C) for low power consumption. Third, thermal stability(Δ) for long retention time to save data. And also these parameters should be achieved at 350oC annealing temperature of the back-end-of line (BEOL) to be commercialized. Among them, thermal stability is closely related with cell size. As a cell size of MTJ decreases to achieve a high density memory device, thermal stability decreases with retention time, thus it is not easy to implement both high density and non-volatile memory device simultaneously by decreasing the cell size of MTJ.
In our study to solve this issue, we propose the p-STT multi-level cell (MLC) magnetic tunnel junction (MTJ) because MLC MTJ can satisfy both high density and non-volatile memory device at the same time. In particular, we design the MTJ structure with dual free layers and MgO tunnel barriers, so that the MTJ can demonstrate four resistance states. In addition, we investigated the effect of the thickness of two free layers and MgO tunnel barriers on two magneto-resistance (MR) and switching voltage. In our experiments, the p-STT MTJ spin-valves were fabricated on 12-inch-diameter Si/ SiO2/W/TiN wafers by utilizing a 12-in. multi-chamber-cluster magnetron-sputtering system under a high vacuum (less than 110-8 Torr) without breaking the vacuum. Then, all samples were subject to ex-situ annealing at 350℃ at a back end of line (BEOL) for 30 minutes under a magnetic field of 3 tesla. In our presentation, we present how to optimize the thicknesses of two free layers and MgO tunnel barriers. In addition, we repot how the magnetic behavior and the resistance of MTJ is affected by magnetic and how the magneto-resistance of MTJ is closely related to the crystallinity of two MgO tunnel barriers.

Acknowledgements

This work was supported by Basic Science Research Program through the National Research Foundation of Korea (NRF) grant funded by the Korea government (MSIP) (No. 2017R1A2A1A05001285)
Ferroelectric Characteristics of Hf0.5Zr0.5O2-Based Mfis and Mfmis Capacitors for Steep-Slope Ferroelectric Field Effect Transistor Applications
Authors: Roh Jangho , Park Hyeon Woo , Lee Yong Bin , Hyun Seung Dam , Kim Keum Do , Moon Taehwan , Lee Young Hwan , Kim Baek Su , Kim Bum Yong , Kim Ho Hyeon , Hwang Cheol Seong 
Published: February 2020

Research of hafnium oxide-based ferroelectric materials has attracted much attention in the community with superior advantages of their compatibility with silicon. Also, negative capacitance (NC) effect from ferroelectric films attracts a great deal of attention because it could be one of the solutions for the high power-consumption issue of field effect transistors (FET). However, since the non-linear Q-V response of semiconductor in the FET structure in conjunction with the domain formation in the ferroelectric layer resulted in complicated device behaviors, it is necessary to understand the physics of the ferroelectric characteristics related to the interactions among the layers such as the depolarization field and charge trapping/injection for sub-60mV/dec subthreshold swing (SS) operation.
In this study, the electrical properties of a Metal-Ferroelectric-Insulator-Semiconductor (MFIS) capacitor with a 7-10nm Hf0.5Zr0.5O2 (HZO) ferroelectric layer and an ultrathin interfacial oxide layer (SiO2) were examined in order to understand the underlying physics of the ferroelectric characteristics (Figure 1 (a)). These properties were compared with those of a Metal-Ferroelectric-Metal-Insulator-Semiconductor (MFMIS) capacitor to analyze the interactions among each layer in the two different structures by pulse measurement. In addition, the ferroelectric characteristics of HZO on semiconductor related to the charge injection through the interfacial oxide layer with different thicknesses and the non-linear Q-V response of semiconductor have been investigated (Figure 1 (b)). Lastly, the effects of different PMA temperatures and HZO thicknesses were also examined and the experimental data were verified by the charge injection-controlled simulation model which was used to simulate the transfer characteristics based on different experimental conditions. (Figure 2).

Figure 1
Study on Interface Engineering of TiN/SiO2 Layers to Reduce the Parasitic Capacitance in CMOS Circuits
Authors: Kim Suncheul , Bae Jong-yong , Park Miseok , Kwon Yong Il , Han Dong-Hoon , Lee Ui-Hyoung , Koo Yoonbon 
Published: February 2020

Recent developments in CMOS (Complementary Metal-Oxide-Semiconductor) technology have heightened the need for high-quality interface between mold and metal line, in order to decrease the RC delay in CMOS circuit. This technical trend indicates that the understanding of the interface reaction between the silicon dioxide (SiO2) and the titanium nitride (TiN) is emerging as an important issue in the thin film deposition process. However, only few researchers have focused on the interface researches to investigate the formation of parasitic capacitance and its material properties of TiN/SiO2 layer.
In this work, we report the formation mechanism of Titanium dioxide (TiO2) on SiO2 surface during the TiN deposition process based on a Plasma Enhanced Chemical Vapor Deposition (PECVD) and Titanium tetrachloride (TiCl4) gas reactions. This research has explored the effects of the partial pressure of TiCl4 gas in the initial step of TiN deposition on the formation of the intermetallic compound of TiN/SiO2 interface layer. The results of atomic composition and the position of valance band of the composite material analyzed by X-ray photoelectron spectroscopy (XPS) reveals that the parasitic capacitance material is the TiO2. The high partial pressure of TiCl4 leads to an increased oxygen-titanium ratio (O/Ti ratio) and a decreased maximum position of valance band at the interface between TiN and SiO2, which is attributed to TiO2 formation. Furthermore, we investigated the effect of the thickness of TiO2 and its Oxygen intensity induced by TiCl4 gas treatment on the change of the parasitic capacitance using X-ray fluorescence (XRF) analysis and Secondary Ion mass spectrometry (SIMS).
(Invited) 2D Materials: Crystal Growth for Future Device Structures
Authors: Colombo Luigi 
Published: February 2020

The isolation of graphene, now over decade ago, has given rise to the revitalization of an old full set of materials, two-dimensional materials (2DM), which have exceptional electrical, chemical and physical properties. Some of the materials under investigation in addition to graphene are hexagonal boron nitride (h-BN), semiconducting, metallic, and superconducting transition metal dichalcogenides (TMD) with a general chemical formula, MX2 where M is for example equal to Mo, W, Ta, Nb, Zr, Ti, and X = S, Se and Te, and others. While graphene is a material with many exceptional properties and h-BN is an excellent 2D insulator, TMD materials provide what neither graphene nor h-BN can, bandgap engineering that, in principle, can be used to create new devices that cannot be fabricated with h-BN and graphene alone. There is hope that 2DM can be integrated to fabricate numerous device types for many applications ranging from inkjet-printed circuits, photonic applications, flexible electronics, and high-performance electronics. However, to fully realize the benefits of these materials, the community will have to work together to define new device structures, device integration schemes, and materials growth processes to help the semiconductor industry make progress toward meeting the original goals of the International Technology Roadmap for Semiconductors (ITRS).
A number of deposition/growth techniques have been used to prepare large area graphene, such as growth on SiC through the evaporation of Si at high temperatures, precipitation of carbon from metals, and catalytic chemical vapor deposition on Cu and Pt. Direct growth of good quality graphene on dielectrics/semiconductors other than SiC with reasonable properties has also been reported recently on Ge. Due to its insulating nature and compatibility with graphene and TMDs, the preparation of large area h-BN is also being developed on both metals and dielectrics. Transition metal dichalcogenides, however, present altogether different opportunities and difficulties in the preparation of low defect density large area single crystals. Vapor transport, chemical vapor deposition (CVD), and molecular beam epitaxy (MBE) are being developed to produce these materials for initial studies of materials physics and device fabrication. In addition, there is some effort in performing simulations to guide growth for both CVD and MBE growers. Therefore, there is an opportunity here to have the crystal growers and the modeling community collaborate to develop high quality materials and processes.
A number of devices structures are currently under evaluation to take advantage of the basic properties of graphene, bi-layer graphene, h-BN and TMDs. Some of the devices are based on tunneling phenomena while others are based on excitonic phenomena. In this presentation I will present the state of the art results of graphene, h-BN, and a few TMD materials and their prospects for future electronic device applications.
(Invited) A New Perspective for Photoelectrochemical Water Splitting: Black TiO2 Nanotubes
Authors: Schmuki Patrik , Liu Ning , Altomare Marco 
Published: February 2020

In the past decade, anodically formed self-organized TiO2 nanotube layers attracted considerable scientific interest (see e.g. reviews [1,2]). This is mainly due to the fact that these layers combine the defined nanotubular geometry with a broad range of functional features inherent to TiO2. Particularly in photoelectrochemical water splitting nanotubular layers have shown remarkable results. The presentation will first give an overview of the most promising features of classic nanotube layers for photocatalysis and then focus on TiO2 nanotube (NT) arrays, converted by a high pressure H2 treatment to anatase-like "black titania"[3,4]. This modification shows a remarkable high open-circuit photocatalytic hydrogen production rate without the presence of any cocatalyst. Other attempts to form black titania, namely using classic reduction treatments (e.g., atmospheric pressure H2/Ar annealing) do not show this surprising effect. We will discuss the main difference caused by the high H2 pressure annealing and the origin of this outstanding activity of black titania.
REFERENCES

Roy, S. Berger, P. Schmuki, Angew. Chem. Int. Ed. (2011), 2904

Lee, A. Mazare, P. Schmuki, CHEMICAL REVIEWS, 114 (2014) 9385

Liu, P. Schmuki et.al. Nano Letters, 14 (2014) 3309

Liu, P. Schmuki et.al. 53 (2014) 14201
Quantum-Enhanced Hydrogen Evolution Reactions in a Monolayer Crystal
Authors: Yan Mengyu , Brischetto Martin , McCune Curt , Yang Jihui 
Published: February 2020

We have demonstrated the Fermi-level dependent catalysis performance in hydrogen evolution reactions 1-2. To go one step further, there is still plenty of room for catalysts to improve their performance if we can modulate the electronic structure without altering the chemical composition. Two-dimensional materials, which have shown unusual layer-dependent electronic structures and the corresponding quantum effects, are an excellent choice to verify this hypothesis. Here, 2H-MoS2 is chosen as an example due to its high activity for hydrogen evolution reactions. It is well known that the in-plane bandgap of monolayer MoS2 (~1.85 eV) is larger than that of the multilayer (~1.30 eV), resulting in inferior conductivity and presumably poorer electrocatalysis activity. Surprisingly, we reveal here that the monolayer 2H-MoS2 electrocatalyst possesses a small overpotential of 30 mV at 70 mA/cm2 and a Tafel slope of 34 mV/dec, considerably superior to that of the multilayer 2H-MoS2 (550 mV at 70 mA/cm2; Tafel slope: 103 mV/dec). Our studies suggest a relationship among the electronic structures, material thickness, and the Helmholtz layer. This work highlights opportunities for developing superior catalysts based on the unusual electronic structures of atomically thin materials.
Reference:

Mengyu Yan; Xuelei Pan; Peiyao Wang; Fei Chen; Liang He; Gengping Jiang; Junhui Wang; Jefferson Z Liu; Xu Xu; Xiaobin Liao, Field-effect tuned adsorption dynamics of VSe2 nanosheets for enhanced hydrogen evolution reaction. Nano Letters
2017,
17 (7), 4109-4115.

Junhui Wang; Mengyu Yan; Kangning Zhao; Xiaobin Liao; Peiyao Wang; Xuelei Pan; Wei Yang; Liqiang Mai, Field Effect Enhanced Hydrogen Evolution Reaction of MoS2 Nanosheets. Advanced Materials
2017,
29 (7).