bluuebunny/crossref_metadata_2025 huggingface dataset:
Area-Selective Atomic Layer Deposition: Understanding the Surface Processes on the Nongrowth Surface
Authors: Agarwal Sumit
Published: December 2020

With feature dimensions of state-of-the-art semiconductor devices moving toward the 5 nm node and beyond, device fabrication based on top-down approaches is becoming ever more challenging. Recently, area-selective atomic layer deposition (ALD) has evolved as a promising method to fabricate well-defined patterns from the bottom-up with atomic-scale accuracy. Within the different approaches for area-selective ALD, preparation of patterned substrates with material-selective organic functionalization offers a promising direction for achieving self-aligned patterns over large areas. In this talk, I will address the interaction of the ALD precursors with the nongrowth surface studied using in situ attenuated total reflection Fourier transform infrared spectroscopy and 4-wavelength ellipsometry. In particular, I will outline the mechanisms that lead to initiation of growth on the passivated nongrowth surface.
The Correlation between the Preferred Orientation and Al Distribution of Al-Doped HfO2 Films By Plasma-Enhanced Atomic Layer Deposition
Authors: Moon Hyoung-Seok , Kim Hyoung Chan , Kim Byung-Jun , Kim Byoung-Koo , Kwon Se-Hun
Published: December 2020

A high dielectric constant (k
= 22.5) Al-doped HfO2 film was prepared on Si substrate by plasma-enhanced atomic layer deposition (PEALD) at a reduced thickness of ~ 30 nm by realizing a (200) preferentially oriented tetragonal structure. The realization of a (200) preferred orientation was able to be obtained by the interface control in PEALD. When using a conventional supercycle that consisted of the Al2O3 and HfO2 subcycles, the dielectric constants of tetragonal Al-doped HfO2 films rapidly decreased from 37 to 8.5 as the film thickness decreased from ~ 92 to ~ 9 nm due to the change of the preferred orientation from (200) to (111). To obtain (200) preferentially oriented tetragonal Al-doped HfO2 thin films at highly thin thickness, a modified supercycle that consisted of the Hf-Al-O subcycle and the HfO2 subcycle was designed to increase Al dopant distribution in HfO2 films. As a result, a (200) preferentially oriented tetragonal Al-doped HfO2 films with a high dielectric constant of 22.5 was obtained at a reduced thickness of ~ 30 nm. Also, the leakage current densities of the Pt/~ 30 nm-thick-tetragonal Al-doped HfO2 films/Si capacitor were about 10-5 A/cm2 for a field strength of -1 MV/cm due to the crystallization after N2 annealing process.
(Invited) Advanced ALD Applications
Authors: Shi Xiaoping
Published: December 2020

CMOS device feature size down-scaling is still continuous. Nowadays it reaches 5nm and beyond. The technology development in semiconductor industry encounters many new challenges. As consequences, new materials and new techniques are required to meet the challenges.

At 45nm technology node, Atomic Layer Deposition (ALD) is introduced for gate stack process. Since then ALD is being used more and more in advanced technology nodes because of its intrinsic process features, e.g. accurate thickness control and excellent step coverage etc. Especially for the reduced feature sizes, ALD exhibits as a powerful technique, not only in gate stack, but also in advanced patterning process (SADP and SAQP) and advanced metallization barrier materials etc.

Hf-based hik material deposited by ALD is widely used in logic gate stack and memory capacitor. Recently Hf-based materials are continuously getting more attentions due to its intrinsic features. It is reported that Hf-based materials can exhibit different resistor stage. Therefore it can be used as memristor in ReRAM. People also report Hf-based materials can be crystalized into orthorhombic phase and thus exhibit ferroelectric characteristics[1,3]. Based on this feature, it can be used in NCFET and FeRAM. In this paper, we can going to review the applications of Hf-based materials deposited by ALD in new memory fields.

Although device down-scaling is still going on, the challenges are tremendous. As an alternative, 3D-IC packaging, stacks different chip together and increases the packaging density and chip performance. Therefore, recently 3D-IC packaging is getting more and more attractive. However, there are many constrains in 3D-IC packaging, e.g. low thermal budget, high aspect ratio structure, excellent film quality etc.. ALD is gradually accepted in 3D-IC packaging due to its intrinsic features. In this paper, we are going to discuss some ALD applications in advanced 3D-IC packaging.

REFERENCES

[1] J. Müller et al, NanoLetters, vol. 12, no. 8, pp. 4318-4323, 2012.

[2] M. H. Lee et al, IEEE J. of the Electron Device Society, vol. 3, no. 4, pp. 377-381, 2015.

[3] M. H. Lee et al, IEEE Electron Device Letter, vol. 36, no. 4, pp. 294-296, 2015.
(Invited) Atomic Layer Deposition for Modification of Various 1D Nanomaterials
Authors: Macak Jan M.
Published: December 2020

One-dimensional nanomaterials – materials with one dimension outside the nanoscale, further noted as 1D NMs – represent a class of very important nanomaterials with continuously increasing importance. Due to their intrinsic features, unique properties and diversity of functionalities, they count among the most widely studied materials nowadays. While considerable research efforts have been spent to synthesize various 1D NMs (e.g. nanopores, nanotubes or nanofibres), limited efforts have been devoted to surface modification and property tailoring of these materials.

However, it is their surface that comes into direct contact with various media (air, gases, liquids, solids) and influences the reactivity, stability and biocompatibility of these materials. The surface and aspect ratio (defined as their diameter to length ratio) influence the performance of these materials in various applications. Considering these facts, it is more relevant to tailor the surface of these materials and to be able to influence their properties and reactivity at the nanoscale, rather than to deal with tailoring their own bulk material composition.

The focus of this presentation is on the modification of two types of 1D NMs– nanotubes and nanofibers. Numerous techniques can be utilized for this purpose, such as for example wet chemical or physical deposition techniques. However, it is only the Atomic Layer Deposition (ALD) that is capable of really uniform and homogenous coating of these 1D nanomaterials, in particular those of very high-aspect ratio.

The presentation will be mianly focused on modification of TiO2 nanotube layers and various nanofibers of various aspect ratios via ALD.

Experimental details and some very recent application examples [1-6] and structural characterizations of these modified materials will be discussed.

Sopha et al (2017), Appl. Mater. Today, 9, 104.

Sopha et al. (2018), Electrochem. Commun., 97, 91.

Ng et al. (2017), Adv. Mater. Interfaces, 1701146.

Dvorak et al. (2019), Appl. Mater. Today, 14, 1.

Sopha et al. (2019), FlatChem 17, 100130.

Motola et al. (2019), Nanoscale 11, 23126.
Next-Generation Li-ion Batteries Made with Spatial Atomic Layer Deposition as an Enabling Technology
Authors: Ameen Mahmoud , Beeker Ide , Haverkate Lucas , Anothumakkool Bihag , Grob Frank , Hermes Dorothee , Huijssen Nico , Khandan del Sepideh , Roozeboom Fred , Unnikrishnan Sandeep
Published: December 2020

Today, Li-ion batteries are key devices in energy storage, with a wide set of applications ranging from mW to kW, such as portable electronics devices, electric vehicles and grid-storage. Typically, high energy density anodes such as Si or Li, combined with Ni- or Li-rich cathodes 1,2 are necessary to obtain the targeted gravimetric energy density (>350 Wh/kg). However, several high-potential redox-chemistries can lead to serious safety and degradation issues during charge-discharge cycling due to oxidative and reductive instabilities 3, that often occur at the electrode-electrolyte interfaces 4. Therefore, for every Li-ion battery chemistry the optimization of these interfaces with chemo-mechanically stable and Li-ion conductive passivation layers is essential in mitigating the non-compatibility of the individual cell components. These interface stabilizing layers can be incorporated either in-situ by using electrolyte additives or ex-situ by chemical and physical methods.

One popular option here is offered by atomic layer deposition (ALD) which is today’s technology of choice to achieve films with superior quality and 3D-conformality with atomic-scale thickness precision. However, conventional vacuum-based temporal ALD is not compatible with industrial high-throughput roll-to-roll battery electrode production. Here, the technique of large-area atmospheric-pressure spatial-ALD (s-ALD) as pioneered by TNO-Holst Centre over a decade ago can offer prime solutions for various applications including thin-film batteries 5. This technique opens up a wide range of cost-effective applications based on materials like metal oxides, nitrides, sulfides, oxysulfides as well as hybrid organic-inorganic material combinations.

In this presentation, we will discuss the growth of several s-ALD films made from Al2O3, TiO2, and ZnO which have been specifically optimized for dendritic Li-growth suppression, interface stabilization, and cathode degradation protection. Next, we will discuss some recent results on the up-scalable s-ALD growth of thin LiPON electrolyte films with a high Li-ion conductivity of >10-7 S/cm, low electronic conductivity of <10-12 S/cm, and high stability against anodic Li-metal during cycling. This electrolyte is also essential in the development of protective layers in liquid and polymer electrolyte-based Li-ion batteries, and in thin-film solid-state batteries with ultra-thin electrolyte layers and planar and 3D topologies.

REFERENCES

S. Myung et al., ACS Energy Lett. 2, 196–223 (2017).

G. Assat and J. M. Tarascon, Nat Energy 3, 373–386 (2018).

H. Ryu et al., Chem. Mater. 3 (30), 1155-1163 (2018).

D. Aurbach et al., Solid State Ionics 148, 405–416 (2002).

P. Poodt et al., J. Vac. Sci. and Technol. A 30, 010802 (2012).
Effect of Co Content on Li-Ni Exchange in NMC Cathode Materials: Atomistic Modeling Insights
Authors: Garcia Juan , Croy Jason R. , Iddir Hakim
Published: December 2020

State-of-the-art, Li-ion batteries used in electric vehicle applications rely on transition metal (TM) oxide chemistries such as LiNiaMnbCocO2 (NMC). Although progress has been steady, several major concerns exist with respect to future implementation of NMC cathodes. The most important material in NMC cathodes is cobalt. High demand, fluctuating prices, has attracted interest in the possibility of competitive, cobalt-free oxides. To gain understanding on the stability of low Co or Co-free cathode materials, we use density functional theory simulations to investigate the effect Co content in LiMn0.5-xNi0.5-xCo2x02 cathodes on Li/Ni anti-site mixing. The results will be presented and discussed in terms of structure-stability and Li/Ni exchange.
Binder Free Carbon Fiber-Based High-Voltage Cathode for Lithium-Ion Batteries
Authors: Tsai Tsung-Yu , Liu Yi-Hung
Published: December 2020

Introduction

With increasing demands of large-scale electronic applications such as electric vehicles (EVs) and hybrid electric vehicles (HEVs), lithium ion batteries (LIBs) with high energy density and power density are desired. To meet the performance requirements, an electrode design that enables to accommodate more active material loading while reducing additives, such as binders and conductive agents, is drawing much attention from researchers. Currently, Al foil is commonly used as the current collectors for cathodes of LIBs. However, corrosion of Al foil could become a serious issue, particularly for long-term cycling at high voltage, deteriorating battery performance [1]. On the contrary, carbon fibers (CFs) are thermally and electrochemically stable, and they can work as good electrical conductors with lightweight, thereby becoming a potential candidate for current collector application[2]. In the current study, we aim to combine nickel-manganese-chromium based cathode material and CFs to develop a composite electrode that can tolerate high-voltage operation.

Experimental

First, heat and acid treatments were carried out to remove resin from CFs surface. Then, electrodeposition of the pretreated CFs was performed in a solution containing nickel, manganese, and chromium ions, to obtain precursor fibers. After that, the precursor fibers went through hydrothermal reaction and calcination, forming a CF-based composite. The composite was further grinded, slurried, and ﬁltrated on a carbon paper to complete the composite electrode. The electrodes were characterized through SEM, TEM, XRD, EDS, XPS and their electrochemical performance was evaluated through a coin cell (CR2032) with lithium metal foil as a counter electrode. In addition, 1 M LiPF6 in a mixture of ethylene carbonate : dimethyl carbonate (1:1 in volume ratio) was used as the electrolyte, and a polyolefin film was used as the separator.

Results and Discussion

From the experiment results, it is convinced that the electrode fabrication process is appropriate to prepare the CF-based composite electrodes. However, properties of the electrodes, including morphology, chemical composition, and crystallinity, vary depending on the fabrication conditions. More interestingly, it is found that Cr doping can stabilize the structure of the Li-Ni-Mn-Cr-O active material with increased crystallinity. The Li-Ni-Mn-Cr-O/CF cathode with proper Cr doping content demonstrates favorable electrochemical performance against high-voltage operation (3.0 ~ 4.9 V). It delivers discharge capacities of 143 and 104 mAh g-1 at 0.2 C and 1 C, respectively. In addition, the cathode possesses excellent cycling stability with a capacity retention over 95% after 100 cycles.

References

[1] M. Wang, M. Tang, S. Chen, H. Ci, K. Wang, L. Shi, L. Lin, H. Ren, J. Shan, P. Gao, Z. Liu and H. Peng, Adv. Mater., 29, 1703882 (2017).

[2] Y. H. Liu, H. H. Lin and Y. J. Tai, J. Alloy. Compd., 735, 580–587 (2018).
Conductive Polymers As Hybrid Battery-Capacitor Electrode Materials
Authors: Schoetz Theresa , Messinger Robert J. , Ponce de Leon Carlos , Bund Andreas , Ueda Mikito , Prodromakis Themis
Published: December 2020

The disruption in next-generation batteries can only be realised by employing both new advanced materials and designs, eventually allowing to holistically achieve new levels of performance, safety and sustainability in a single battery system. To close the gap between high power and energy per unit weight, new materials are needed that can act as a battery and capacitor simultaneously. Conductive polymers, e.g. poly(3,4-ethylenedioxythiophene) (PEDOT), used with ionic liquids or semi-solid ionogels have recently attracted attention as hybrid battery-(pseudo)-capacitor systems, achieving a specific capacity, energy, and power of 40-180 Ah kg-1, 50-230 Wh kg-1, and 30-140 W kg-1 when used as positive electrodes in rechargeable aluminium batteries 1-4. In addition, the polymer composites are non-flammable, non-toxic, economically available and recyclable at low-cost. In comparison to other charge storage materials, like graphite, conductive polymers are less limited by their capacity as the electrode architecture can be redesigned from a conventional 2D design to an interconnected 3D electrode-electrolyte network, allowing a higher active surface, shorter charge transfer and ion diffusion paths for fast charging (up to 80C 4), and controllable electrode shapes/sizes (Figure A 3). The performance of conductive polymers can be tailored by their synthesis path and conditions 1,5. The relationship between electrode fabrication, underlying operating mechanisms, and performance was studied by in operando methods such as electrochemical atomic force microscopy (EC-AFM), and electrochemical microgravimetry (EQCM) 3.

The main achievement is the visualisation of reversible morphological modifications at the nano-scale (Figure B and C 3) of the conductive polymer as a function of state-of-charge. Such changes influence significantly the viscoelastic material properties, which are linked directly to the electrochemical fabrication process 5. Overall, the findings provide an explanation why conductive polymers behave like a hybrid battery-(pseudo)-capacitor (Figure D), setting a new standard for how energy storage can be approached.

[1] Heinze, J. et al. Chemical Reviews
2010, 110, 4724–4771.

[2] Hudak, N.S. The Journal of Physical Chemistry
2014
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118, 5203–5215.

[3] Schoetz, T. et al. Journal of Materials Chemistry A
2018, 6, 17787–17799.

[4] Schoetz, T. et al. Journal of the Electrochemical Society
2020, 28, 101176.

[5] Schoetz, T. et al. Electrochimica Acta
2018
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263, 176–183.

Figure 1
Poly(benzoquinonyl disulfide) as an Active Material for Both Lithium and Magnesium Batteries
Authors: Tran Anh , Leprêtre Jean-Claude , Berthelot Romain , Alloin Fannie
Published: December 2020

The undeniable benefit of lithium-ion (LIB) batteries for the development of a more environmentally friendly economy was recognized by the 2019 Nobel Prize in Chemistry. However, relying only on LIBs to energy storage will put considerable strain on lithium and cobalt resources used in these batteries. Therefore, alternative battery technologies other than LIBs are desirable to satisfy our growing demand for energy. Magnesium-ion batteries offer many distinct advantages over LIBs, including the high earth-abundance of magnesium, its high energy density and reversible dendrite-free deposition1. Organic materials are receiving an increasing amount of attention as electrode materials for future post lithium-ion batteries due to their versatility and sustainability2. In order to propose organic cathode with both high potential and specific capacity, new polymer based on hydroquinone sulfide, poly(benzoquinone disulfide) (PBQDS), were prepared in order to apply in both lithium and magnesium batteries. Diglyme and sulfolane with both LiTFSI and Mg(TFSI)2 were selected in order to evaluate the entire potentiality of the active material3. First of all, the electrochemical responses of PBQDS in lithium and magnesium based electrolytes was performed in a cavity electrode. The shapes of the cyclic voltammetry curves (Figure 1) are very close in term of potential and ΔEpeak in both lithium and magnesium systems at a relative high scan rate i.e. 1 mV s-1. An improvement of the redox couple reversibility seems to be observe in Mg form, with a ΔEpeak= 400 mV at a potential of 0.3 V vs Fc+/Fc (near 3.5 vs Li+/Li). Promising first results were obtained with PBQDS using glyme + LiTFSI electrolyte, in a coin cell configuration, indeed a stable capacity of 160 mAh g-1 was obtained at C/10 after 70 cycles, whereas 120 mAh g-1 was obtained at C in glyme based electrolyte. In order to improve, the electrochemical performances, especially at high C-rate, the particle size was reduced by controlled grinding. The effect of the PBQDS particle size on the electrochemical performances was under process. The electrochemical investigations in both Mg and Li based electrolytes will be presented in regard to the electrolyte nature and the PBQDS morphology.

H. D. Yoo, I. Shterenberg, Y. Gofer, G. Gershinsky, N. Pour, D. Aurbach, Energy Environ. Sci., 2013, 6, 2265–2279.

Poizot, F. Dolhem, Energy Environ. Sci., 2011, 4, 2003

H. Dong, Y. Liang, O. Tutusaus, R. Mohtadi, Y. Zhang, F. Hao, Y. Yao, Joule 2019, 3, 1–12

Figure 1
(Invited) Lithium Ion Transfer Kinetics of Size Regulated TiO2(B) Nanosheets with Vertical, Random, and Horizontal Alignment for High Rate Lithium Ion Capacitors and Batteries
Authors: Sugimoto Wataru , Nagatani Itsuki , Yoshida Tomohiro , Takimoto Daisuke , Mochizuki Dai , Hideshima Sho
Published: December 2020

TiO2(B) has a high theoretical capacity of 335 mAh g-1 for Li+ intercalation and thus is a promising candidate as negative electrodes for lithium-ion capacitors and Li-ion batteries. For high rate lithium-ion transfer, it is important to shorten the Li+ diffusion path by using nanostructured TiO2(B). In this work, TiO2(B) nanosheets with different equivalent diameter D
e of 300 nm and 30 nm were prepared. In addition, the orientation of the TiO2(B) nanosheets was manipulated by altering the deposition method and drying process. For large-sized TiO2(B)(300 nm) nanosheet electrodes, the orientation effect was not clear and the amount of lithiation (SOC) was almost the same. Even at a rather low loading of 0.35 mg/cm2, only 1/5 of the theoretical capacity could be intercalated (Li0.2TiO2, 20% SOC) at 0.2C rate. By downsizing TiO2(B) to D
e=30 nm, a two time increase in rate performance (Li0.4TiO2 at 0.2C) was obtained for vertically-aligned electrodes. Although the orientation of small-sized TiO2(B) had a large influence on Li+ transfer kinetics, 100% SOC could not be achieved even at 0.2C, suggesting the lack of electronic conductivity as a governing factor.1

To better understand the Li+ transfer kinetics, the lack of electronic conductivity was circumvented by adopting a vertically aligned reduced graphene oxide (V-rGO) electrode2 as a porous current collector. Three different size TiO2(B) nanosheets (300, 150, and 70 nm) were deposited on V-rGO at a loading of 0.20 mg/cm2. CVs at 0.5 mV/s reveals that 334 and 332 mA/g (100% SOC) is obtained for TiO2(B)/V-rGO with D
e=70 and 150 nm, respectively. On the other hand, for the 300 nm sized TiO2(B)/V-rGO, only 55% SOC was achieved (186 mAh/g). The trend in Li+ transfer kinetics becomes clearer at higher scan rate (10 mV/s) with the capacity scaling with decreasing equivalent diameter; 89, 194, and 233 mAh/g for D
e=300, 150 and 70 nm TiO2(B)/V-rGO. Discussion on results of b-value analysis and Li+ penetration depth will be given in detail in the talk.

This work was partially supported by an Advanced Low Carbon Technology Research Development Program (JST-ALCA, JPMJAL1008).

[1] T. Yoshida, D. Takimoto, D. Mochizuki, W. Sugimoto, Electrochem., in press.

[2] D. Mochizuki, R. Tanaka, S. Makino, Y. Ayato, W. Sugimoto, ACS Appl. Energy Mater.,2(2), 1033 (2019).
Investigation of Cause of Deterioration of Redox Mediator Fixed Electrode for Li-Air Battery
Authors: Miyashiro Kae , Mochizuki Takeshi , Momma Toshiyuki , Matsuoka Koji , Nagatsuka Tomomi
Published: December 2020

Currently, lithium-ion batteries are widely used as storage devices and further capacity increase of battery is required, while lithium-ion batteries are reaching the theoretical capacity. Lithium-air batteries are expected to be realized in the future, as power storage devices with even higher energy density are required due to the development of IoT and the spread of electric vehicles with a low environmental load. However, many problems remain for the practical application of lithium-air batteries, and it is difficult to obtain sufficient discharge capacity as an insulating discharge product covers the cathode as the reaction progresses, as a problem during discharge. In addition, during charging, a large overvoltage is required for the charging reaction that decomposes lithium peroxide, which is an insulating solid, generated during discharging. Therefore, redox mediators that mediate these charge / discharge reactions are drawing attention. However, when the redox mediator is added to the electrolyte, the redox mediator, which should mediate the cathode reaction, diffuses toward the anode and reacts with lithium, or the redox mediator oxidized at the cathode during charging is reduced at the anode and overcharged by the redox shuttle. It has become a problem. Therefore, in our research, we are fixing the redox mediator on the surface of the cathode in order to prevent it from diffusing into the anode and reacting with lithium metal.

So far, our laboratory has selected TEMPO (2,2,6,6-tetramethylpiperidine 1-oxyl) as a redox mediator and produced a TEMPO immobilized CP (carbon paper) cathode. When this cathode was used, reduction of charging overvoltage and suppression of overvoltage were confirmed, suggesting a redox mediator effect and a redox shuttle forcing effect(Fig.1). However, as a result of carrying out a charge / discharge cycle test using this, it was confirmed that the charge overvoltage increased after repeating charge / discharge cycle(Fig.2).

CV measurements were conducted in Ar atmosphere before and after the charge and discharge processes, as revealed that the redox peaks of TEMPO became smaller after charge and discharge, suggesting decreased amount of reactive TEMPO. Observation of the cathode after charging and discharging with SEM or XPS to investigate the cause of deterioration revealed no clear consideration. The deterioration was considered to be the complicated structure of carbon paper with entangled carbon fibers.

Figure 1
Dependence of Impedance Response of Li-S Battery on Polysulfide Solubility of Electrolyte I - Initial Stage of Discharge
Authors: Hashizume Kota , Momma Toshiyuki , Yokoshima Tokihiko , Togasaki Norihiro , Nakao Aiko , Nara Hiroki , Osaka Tetsuya , Yaji Toyonari
Published: December 2020

Lithium-sulfur (Li-S) battery has higher theoretical specific capacity than commercial lithium-ion batteries. However, one of serious problems in sulfur cathode to be solved to realize a commercial Li-S battery is polysulfide dissolution, causing lowering charge-discharge capacity and round-trip efficiency. In previous studies, glyme-Li+ solvent ionic liquid (SIL)1) and polypyrrole film containing ionic liquid2) were proposed to mitigate dissolution of polysulfide. Meanwhile, dependence of sulfur cathode’s reaction mechanism on polysulfide solubility of electrolyte is still unclear. In this study, electrochemical impedance spectroscopy (EIS) at various depth of discharge was performed in two types of lithium-sulfur batteries using electrolytes with different polysulfide solubility. This paper describes that polysulfide solubility in electrolyte largely influences the impedance response at initial stage of discharge in Li-S batteries. For cathode and electrolyte, X-ray absorption near edge structure (XANES) was also performed in order to analyze the valence of sulfur species at various depth of discharge.

Figure 1 shows discharge curves of Li-S cells with polysulfide soluble electrolyte (1M LiTFSI in 1,3-dioxolane (DOL)/1,2-dimethoxyethane (DME) 1:1 (v/v)) and with polysulfide insoluble SIL electrolyte (Li(G3)TFSI/hydrofluoroether (HFE) 1:4 (v/v)). Figure 2 (a) and (b) show Nyquist plots obtained by the cells using DOL/DME and SIL, respectively. A remarkable difference was observed in the diameter of semicircles in a frequency range of 1 kHz – 10 Hz; in both cases, semicircle decrease as discharge progression in the same manner, while decrease of the semicircles with DOL/DME was more notable. In addition, another semicircle in a frequency range of 10 Hz - 1 Hz was observed only in the Nyquist plots with SIL electrolyte. These results indicate that the semicircles in higher frequency region (1 kHz – 10 Hz) are attributed to dissolved polysulfide and the semicircle in lower frequency region (10 Hz – 1 Hz) is attributed to undissolved polysulfide. XANES measurement confirms that signal by sulfur (2472 eV) decreased until potential reached 2.1 V with DOL/DME and until 1.5 V with SIL. These results indicate that reduction of sulfur proceeds until 2.1 V with DOL/DME and until 1.5 V with SIL which is in good agreement with the result from impedance response by EIS.

Acknowledgement

This work was partly supported by Advanced Low Carbon Technology Research, Development Program Special Priority Research Area “Next-Generation Rechargeable Battery” (ALCA-Spring) from the Japan Science and Technology Agency (JST) (Grant Number JPMJAL1301).

Reference

(1) Kaoru Dokko et al., Journal of the Electrochemical Society, Volume 160, Issue 8, A1304-A1310 (2013).

(2) Natsuki Nakamura et al., J Power Sources, 274, 1263-1266 (2015).

Figure 1
Dependence of Impedance Response of Li-S Battery on Polysulfide Solubility of Electrolyte II - Mid - End Stage of Discharge
Authors: Yokoshima Tokihiko , Togasaki Norihiro , Nara Hiroki , Nakao Aiko , Osaka Tetsuya , Hashizume Kota , Hirayanagi Tomoe , Momma Toshiyuki , Yaji Toyonari
Published: December 2020

Sulfur is a promising cathode material for the lithium based battery because of its advantages such as eco-friendness, abundance in nature, and high theoretical capacity of 1675 mAh g-1. However, sulfur cathodes are not without their own intrinsic problems such as low ionic and electronic conductivity, large volumetric expansion upon lithiation from S8 to Li2S, and the dissolution of so-called polysulfide intermediates (Li2Sx where x represents a value between 4 and 8). In previous studies, glyme-Li+ solvent ionic liquid (SIL)1) and polypyrrole film containing ionic liquid2) were proposed to mitigate dissolution of polysulfide. Meanwhile, dependence of sulfur cathode’s reaction mechanism on polysulfide solubility of electrolyte is still unclear. In this study, electrochemical impedance spectroscopy (EIS) at various depth of discharge was performed in two types of lithium-sulfur batteries using electrolytes with different polysulfide solubility. This paper describes that polysulfide solubility in electrolyte largely influences the impedance response at mid - end stage of discharge in Li-S batteries.

Figure 1 shows discharge curves of Li-S cells with polysulfide soluble electrolyte (1M LiTFSI in 1,3-dioxolane (DOL)/1,2-dimethoxyethane (DME) 1:1 (v/v)) and with polysulfide insoluble SIL electrolyte (Li(G3)TFSI/hydrofluoroether (HFE) 1:4 (v/v)). Figure 2 (a) and (b) show Nyquist plots obtained by the cells using DOL/DME and SIL, respectively. A remarkable difference was observed in the diameter of semicircles in lower frequency range of 10Hz – 0.1 Hz at potential of 2.1 - 1.5 V. The semicircle was observed with SIL at 2.1 V, and the diameter of the semicircle increased with discharge progression. No semicircle was observed at 1.9-1.5V. On the other hand, no semicircle with DOL/DME was observed at 2.1 - 1.5 V. However, impedance response at 2.1 V changed to that at 1.9 - 1.5V. The difference at 2.1V was attributed to DOD and/or state of polysulfide in electrolyte. There was no large difference of impedance response with these electrolytes at 1.9 V -1.5 V. It is thought that similar (semi-) solid-state reactions without electrolyte was occurred, because of no effect of solving polysulfide of Li2S2 and Li2S in both electrolytes.

Acknowledgement

This work was partly supported by Advanced Low Carbon Technology Research, Development Program Special Priority Research Area “Next-Generation Rechargeable Battery” (ALCA-Spring) from the Japan Science and Technology Agency (JST) (Grant Number JPMJAL1301).

Reference

(1) K. Dokko et al., J. Electrochem. Soc., 160, A1304-A1310 (2013).

(2) N. Nakamura et al., J Power Sources, 274, 1263-1266 (2015).

Figure 1
(Invited) Heterogeneous Integration and Co-design of Memristor and MOSFET for AI Application
Authors: Xi Yue , Gao Bin
Published: December 2020

Recent advances in AI bring great challenges on the computing hardware. Memristor based neuromorphic computing can improve the computing density and energy efficiency significantly. However, how to integrate memristive materials and design mixed circuit with advanced CMOS platform is a key challenge. In this presentation, I will talk about our recent progress on heterogeneous integration of memristor and MOSFET. Million-level one-transistor-one-resistor (1T1R) cells can be integrated on a chip. Then I will discuss the co-design technology for memristor/MOSFET mixed circuits. A general purpose neuromorphic computing chip was designed and fabricated to process deep neural networks. I will also introduce our new hybrid training method for eliminating the accuracy loss caused by device variations.
(Invited) How Far Can We Push Conventional Silicon Technology and What are the Future Alternatives?
Authors: Saraswat Krishna C.
Published: December 2020

Si CMOS technology has dominated the microelectronics industry, with continued scaling. However, future scaling is reaching practical and fundamental limits. Currently, strained-Si channel with high-k/metal gate is the dominant technology. Si FinFETs have provided further innovation to improve electrostatic control of the channel and thus reduce leakage. However, performance enhancement of Si CMOS is beginning to saturate with scaling to nanoscale. To go beyond these limits novel materials and structures are being aggressively studied. Higher mobility semiconductors, like Ge, GeSn and III-Vs, together with innovative device structures could increase drive current and reduce power consumption and delay. Carbon nanotubes and graphene offer very high mobility, excellent electrostatic control of the channel but have problems in manufacturability. Graphene also has the problem of ~0 bandgap making it not very useful for logic. Recently 2D materials like metal sulfides, telurides and selenides have emerged as potential candidates for nanoscale devices.

Is Ge PMOS and III-V NMOS co-integration on Si feasible or a headache for the manufacturing folks? Can we have all Ge or all III-V CMOS or it is just a fantasy? Can CNT FETs become manufacturable? Are 2D materials more promising? This talk will try to answer some of these questions.
Contact Resistivity of Highly Doped Si:P, Si:As, and Si:P:As Epi Layers for Source/Drain Epitaxy
Authors: Rosseel Erik , Porret Clement , Hikavyy Andriy Yakovitch , Loo Roger , Tirrito Matteo , Douhard Bastien , Richard Olivier , Horiguchi Naoto , Khazaka Rami
Published: December 2020

With the downscaling of the CMOS transistor dimensions, the reduction of the external resistance is playing an important role in the overall device optimization. For NMOS devices, highly P-doped Si:P epitaxy is typically used to lower the source/drain and contact resistance [1]. In this work we report on the use of As as a dopant and compare the layer characteristics and contact resistivity of highly doped epitaxial Si:P, Si:As, Si:P:As layers and Si:As/Si:P bi-layers grown on 300 mm Si (100) substrates. As is found to incorporate more efficiently into the epi layer compared to P but gives rise to a lower tensile strain [2]. Good quality epitaxial layers can be obtained with As concentrations as high as 10% (Fig. 1). In comparison to Si:P a reduced diffusion is confirmed for Si:As after spike and laser anneal, making the layer an interesting candidate for an extension liner [2,3]. In general, the dopant activation and carrier mobility of the Si:As and Si:P:As layers after epitaxy is lower than that of Si:P as determined by micro-Hall measurements (Fig. 2a). Only in some specific cases (e.g. for concentrations below ~3% and non-selective processes), we can observe an enhanced activation due to the co-doping of P and As which we attribute to an energetically favorable AsxV vacancy complex formation at low As concentration [4]. The contact resistivity was extracted using a Multi-Ring Circular Transmission Line Model for a Ti based contacting scheme [5]. The contact resistivity of Si:P, Si:As and Si:P:As layers with different concentrations obtained by selective and non-selective epitaxy was compared and the effect of a post-epitaxy millisecond laser anneal was studied (Fig. 2b). Excellent contact resistivities down to ~2E-9 Ohm.cm2 could be found at high doping levels. A clear correlation was observed between the resistivity/contact resistivity and activation levels obtained by micro-Hall measurements. Within the set of studied processes, As doping is not bringing substantially lower contact resistivities compared to P doping, for comparable chemical doping concentrations. Still, As remains an attractive dopant for extension liners because of its lower diffusion constant.

References

[1] E. Rosseel et al., ECS Trans. 75(8), pp.347-359 (2016).

[2] E. Rosseel et al., ECS Trans. 93(1), pp. 11-15 (2019).

[3] S. Mochizuki et al.,IEEE Int. Electron Devices Meeting 2018, p. 811 (2019).

[4] N. Nakazaki et al., EMRS 2019 B.IX.3

[5] H. Yu et al., IEEE Electron Device Letters, 36(6), pp. 600-602 (2015).

Figure 1
(Invited) Stacking Faults in 3C-SiC: From the Crystal Structure, to the Electrical Behavior
Authors: La Via Francesco , Zimbone Massimo , Scuderi Viviana , Calabretta Cristiano , Bongiorno Corrado , Giannazzo Filippo , Fiorenza Patrick , Muoio Annamaria
Published: December 2020

Many attractive mechanical and electrical properties make silicon carbide (SiC) a material of interest in both electronic devices and sensors for nowadays technology (sustainable energies, hybrid vehicles, low power loss inverters). Silicon carbide exists in nature in several crystalline structures, called polytypes, differentiated by the stacking sequence of the tetrahedrially bonded Si-C bilayers. The only possible cubic structure, 3C-SiC, is obtained when the bilayer stacking is of the kind ABCABC..., resulting in a pure zinc-blende structure. 3C-SiC growth on Si is allowed within chemical vapour deposition (CVD) reactors, which would ensure a very high purity of the resulting product. The interface between 3C-SiC and Si is the origin of a high density of planar and volume defects, such as microtwins, anti-phase boundaries and stacking faults in the epilayer and voids in Si underneath the hetero-interface. Most of these defects, considered killers for devices, however, reduce their density, and some are totally annihilated, when very thick (several tens of microns) 3C-SiC epitaxial films are realized. The main defects that remain also after the growth of several tens of microns are the Stacking Faults (SFs). Three main SFs have been observed in 3C-SiC: the intrinsic one where only one plane is shifted with respect to the lattice position and two extrinsic SFs where two or three layers are shifted. In these last cases we observe locally the same crystallographic structure of the hexagonal polytypes: 4H-SiC and 6H-SiC. In the last period a large investigation has been done on these defects to see the crystallographic structure of these defects, the interactions between different SFs, the influence of the SFs on the internal stress of the material, the effects of several growth parameters (temperature, doping, growth rate, ...) on the density and evolution of these defects. Finally also several local electrical measurements by C-AFM has been done to understand the effect of these defects on the electrical behaviour of the devices.

In Fig. 1 a three different HRTEM images of three different SFs are reported. It is possible to observe the different crystallographic structure of these defects. In Fig. 2 the interaction between these defects is reported. It is possible to observe that the SFs can annihilate or generate or close. The growth parameters have a large influence on the evolution of these defects. In Fig. 3 can be observed that, decreasing the growth rate and the growth temperature, the SFs density decreases. In Fig. 4 it is reported the effect of the doping on the SFs. Increasing the nitrogen concentration the SFs density decreases and the average length increases.

At the conference more details on the SFs structure, the effect of these defects on the stress and on the electrical characteristics of the devices will be given.

Figure 1
(Invited) Application of a Laboratory-Based Scanning XPS/Haxpes Instrument for the Characterization of Buried Interfaces
Authors: Artyushkova Kateryna , Mann Jennifer , Newman John , Inoue Risayo , Watanabe Katsumi , Yamazui Hiromichi , Vanleenhove Anja , Zborowski Charlotte , Conard Thierry
Published: December 2020

X-ray Photoelectron Spectroscopy (XPS) is a widely used surface analysis technique with many well established industrial and research applications. The surface sensitivity (top 5-10 nm) of XPS and its ability to provide short-range chemical bonding information make the technique extremely popular in materials characterization and failure analysis laboratories. While its surface sensitivity is an important attribute, in some cases, the depth of analysis of XPS is not sufficient to analyze buried interfaces without first sputter etching the sample surface. However, sputter etching can often lead to alterations of the true surface chemistry. An alternative to sputter etching the sample is Hard X-ray Photoelectron Spectroscopy (HAXPES), available at some synchrotron facilities. HAXPES utilizes X-rays typically defined as having energies greater than 5 keV. By increasing the photon energy of the X-ray source, the mean free path of photoelectrons is increased, resulting in an increased information depth obtained from the sample. Depending on the energy used, these hard X-rays can provide depths of analysis three or more times than that of soft x-rays used on conventional XPS systems. HAXPES measurements are, therefore, more sensitive to the bulk, and contributions from the surface are minimized.1,2 This presentation will describe a laboratory-based instrument, the PHI Quantes, equipped with two scanning microprobe monochromated X-ray sources, Al Kα (1486.6 eV) and Cr Kα (5414.9 eV), thus enabling both traditional XPS and HAXPES experiments in the same instrument. Combining both soft and hard X-ray analyses, we can gain an even better understanding of composition with depth and information at buried interfaces. References

Kobayashi, K. Hard X-ray photoemission spectroscopy, Nucl. Instr. Meth. Phys. Res. A
2009, 601, 32-47.

Fadley, C.S. Hard X-ray Photoemission: An Overview and Future Perspective. In Hard X-ray Photoelectron Spectroscopy (HAXPS); Woicik, J. C., Ed; Springer: Switzerland 2016.
Thermal Silicidation of Ni/SiGe and Characterization of Resulting Silicide Films Using Raman Spectroscopy and X-ray Diffraction
Authors: Yoo Woo Sik , Kang Kitaek , Ishigaki Toshikazu , Kim Jung Gon , Hasuike Noriyuki , Harima Hiroshi , Yoshimoto Masahiro
Published: December 2020

For advanced application specific devices, combinations of Si/Ge, Ge/Si, Si1-xGex/Si are frequently introduced in the device fabrication process. Epitaxy, condensation and annealing processes are commonly used for controlling the Ge content to a desired level. Strain and crystallinity can be affected by a small variation in composition or Ge content, which can result in device performance deterioration or failure. Thus, the composition, strain and crystallinity must be carefully monitored and controlled throughout the manufacturing process. The electrode formation process is also very critical for successful device fabrication. Any spikes and/or electrically active defects near junctions can be fatal to the device yield. Silicidation processes and resulting silicides must be investigated as much as possible using various non-invasive material characterization techniques.

In this study, we report the thermal silicidation characteristics of Ni/Si1-xGex with various Ge content under different annealing temperatures in the range of 225oC ~ 400oC in N2 ambient. Thermal silicidation was performed in a stacked hotplate-based SAO-302LP system designed for 300mm wafers. For resulting silicide characterization, measurements of sheet resistance, Raman spectra, X-ray diffraction curves as well as scanning electron microscopy (SEM) observations were performed. We have studied Ge content and annealing temperature dependence on the resulting electrical and crystallographic silicide characteristics.

Figure 1 shows 647nm excited Raman spectra and X-ray diffraction (XRD) curves from reference Si, and resulting silicide from Ni/Si0.75Ge0.25 before and after annealing under at 235oC, 310oC and 400oC.

Raman spectra and sheet resistance measurements showed silicide formation and silicide layer thickening with increasing annealing temperature. XRD curves clearly indicated the change of crystalline phase of resulting silicide with annealing temperature increase. Various aspects of thermal silicidation and its characterization will be discussed at the conference.

Figure 1
Rationally Designed 3D Graphene Hollow Spheres Towards Building High Energy – High Power Energy Storage System with Long Durability
Authors: Thangavel Ranjith , Oh Woong , Jeong Mihee , Yun Soyeong , Choi Munhyeok , Lee Yun-Sung , Yoon Won-Sub
Published: December 2020

Functional materials with high energy density – high rate capabilities have continued to gain importance, and are extensively studied for next-generation energy storage applications.[1] The ongoing challenge is to elevate the power density of batteries on par with capacitors, while holding the energy density and cycle life.[2] The sluggish intercalation kinetics, and continuous transition metal dissolution in conventional electrodes hampers the realization of high power, and highly stable devices.[3] To overcome the kinetic issues, we rationally designed graphene hollow nanospheres (GHNS) with dual heteroatoms (nitrogen and sulfur) as both anode and cathode for Na-ion based energy storage system. The self-assembly of 2D graphene into a highly connected 3D architecture facilitates facile Na-ion storage, while the nitrogen and sulfur hetero atoms infiltrated in the carbonaceous matrix elevates the kinetics of the GHNS. The full-cell based on GHNS electrodes displays a high operating voltage, high energy density (121 Wh kg−1 at 100 W kg−1), and high power density (51 kW kg-1). Further, the sodium-ion storage system can render remarkable cycling stability of ~85% retention after 10,000 cycles (~0.0015% decay per cycle). Development of such nanostructured functional materials could establish a trade‐off relationship between high energy and high power devices.

References

[1] J. R. Miller, P. Simon, Science 2008, 321, 651.

[2] H. Jiang, P. S. Lee, C. Li, Energy Environ. Sci. 2013, 6, 41.

[3] R. Thangavel, B. Moorthy, D.K. Kim, Y.-S. Lee, Adv. Energy Mater. 2017, 7, 1602654.
Electrochemical Activation for Improved Cycle Life of Li-Se Batteries
Authors: Kim Mihyun , Um Ji Hyun , Jin Aihua , Yu Seung-Ho
Published: December 2020

Recently, the lithium-selenium (Li-Se) batteries have received enormous interest as a promising candidate for next-generation rechargeable batteries. Although selenium is similar to sulfur because they belong to the same group (chalcogenides), Li-Se battery has an advantage beyond lithium-sulfur batteries. Selenium is less reactive and more controllable in an electrochemical cell. Moreover, it has a much higher electrical conductivity than sulfur, which enables high utilization of selenium. However, one problem is the dissolution of lithium polyselenides. The lithium polyselenides aggregate at the cathode surface, resulting in increased cell impedance. To solve this problem, many experiments have been suggested but they were difficult to conduct. Herein, a simple and facile method is introduced to improve cycle performance. Before the fully discharge process, the Li-Se cell was activated electrochemically. This activation leads to a significant improvement in cycle performance by the redistribution of selenium on the electrode.