bluuebunny/crossref_metadata_2025_split huggingface dataset:
Investigating Failure of Li-Ion Batteries Using in Operando Electrochemical-Acoustic Time-of-Flight Analysis
Authors: Hsieh Andrew , Bhadra Shoham , Gjeltema Peter J , Steingart Daniel A 
Published: February 2020

Electrochemical-Acoustic Time-of-Flight (EAToF) analysis takes advantage of the fact that in all closed electrochemical energy storage systems, regardless of the reaction mechanism (intercalation, dissolution/reprecipitation, phase change, etc.) the density and elastic modulus of each electrode changes as a function of its state of charge (SOC). This, in turn, affects how sound waves behave as they travel through the cell. Additionally, as a battery is cycled, progressive formation/degradation of critical surface layers, mechanical degradation of electrodes, consumption of electrolyte, etc. also affect the behavior of acoustic waves passing through the cell. Thus, the distributions of density and modulus within the cell as well as the rates of change of these distributions (and the resulting effect on the acoustic echoing behavior) can act as a fingerprint for the state of health (SOH) of the cell. In a previous study, we have demonstrated this in operando EAToF analysis experimentally using ultrasonic pulses during normal cycling of a wide variety of battery chemistries and form factors.
Here, we focus on the effect of long-term cycling on the electrochemical-acoustic fingerprints, particularly for commercially-available Li-ion 18650 type cells. We examine how the EAToF patterns evolve as a function of depth of discharge and cycling rate, and also investigate the effect of “abusive” cycling conditions (e.g., elevated temperatures, over-charge/discharge, etc. as prescribed by UN 38.3 and IEC 62133 standards) on acoustic behavior. Two failure modes that we study in detail are electrolyte consumption and lithium plating in Li-ion batteries, and we verify failure modes with post-mortem analysis. Our results show that the fingerprints from EAToF analysis, perhaps in combination with various numerical analysis methods, can be correlated not only to SOC during normal cycling, but also to SOH during extended cycling and catastrophic failure events.
Side-Chain Conducting and Phase-Separated Polymeric Binders for High Performance Silicon Anodes in Lithium-Ion Batteries
Authors: Zhao Hui , Park Sang-Jae , Ai Guo , Yang Wanli , Wang Cheng , Liu Gao 
Published: February 2020

Here we describe a class of electric-conducting polymers that conduct electrons via the side chain π–π stacking. These polymers can be designed and synthesized with different chemical moieties to perform different functions, extremely suitable as a conductive polymer binder for lithium battery electrodes. A class of methacrylate polymers based on a polycyclic aromatic hydrocarbon side moiety, pyrene, was synthesized and applied as an electrode binder to fabricate a silicon (Si) electrode. The electron mobilities for PPy and PPyE are characterized as 1.9 × 10–4 and 8.5 × 10–4 cm2 V–1 s–1, respectively. These electric conductive polymeric binders can maintain the electrode mechanical integrity and Si interface stability over a thousand cycles of charge and discharge. The as-assembled batteries exhibit a high capacity and excellent rate performance due to the self-assembled solid-state nanostructures of the conductive polymer binders. These pyrene-based methacrylate binders also enhance the stability of the solid electrolyte interphase (SEI) of a Si electrode over long-term cycling. The physical properties of this polymer are further tailored by incorporating ethylene oxide moieties at the side chains to enhance the adhesion and adjust swelling to improve the stability of the high loading Si electrode.

Figure 1
Inhibition Performance Study of Aqueous Vanadate Species on Mg Alloys
Authors: Li Jichao , Hurley Belinda , Buchheit R. 
Published: February 2020

This work presents the corrosion inhibition performance of vanadate on Mg alloy AZ31 and its dependence on pH and immersion time. Aqueous vanadate speciation, which has been shown to have a strong effect on corrosion inhibition, is a function of solution pH. The pH dependence of vanadate corrosion inhibition is, therefore, attributed to the pH dependence of vanadate speciation. Immersion in tetrahedrally coordinated vanadate species, present in neutral and alkaline solution, was shown to decrease corrosion rate and increase pitting potential, both of which were enhanced with longer immersion times. Alternatively, exposure to octahedrally coordinated vanadate, which predominates in acidic solution, only slightly decreased the corrosion rate. An acidic solution (octahedrally coordinated speciation) was adjusted to alkaline conditions and samples were then immersed in the adjusted alkaline solution. Inhibition on these samples was weaker than that of samples immersed in alkaline solutions that had never been acidic. Regardless of speciation, vanadate was shown to provide limited inhibition on cathodic reaction kinetics (hydrogen reduction reaction). Anodic inhibition was observed on samples treated in solutions containing tetrahedral species. Inhibition performance was also characterized by electrochemical impedance spectroscopy. Aqueous vanadate in 0.1 M NaCl increased the total impedance at all pH values (5, 7.7, 9.2), with enhanced results observed with increasing immersion time. The greatest increase in impedance for a given immersion time occurred at pH 9.2, which is consistent with the inhibition determined by corrosion rate. SEM showed that vanadate forms a film across both secondary particles and the Mg matrix, and it provided qualitative evidence that inhibition efficiency increased as the pH of the exposure solution increased. XPS results indicate that vanadate film formation is associated with the reductive adsorption of vanadate by Mg. Exposure at a pH of 5 produced vanadate predominated by V4+. Exposure at pH values of 7.7 and higher, however, produced vanadate containing predominantly V3+.
Role of Confinement in Localized Corrosion
Authors: Puranik Rohit , Quesnel David J 
Published: February 2020

In context of localized corrosion, the dissolution of metallic species into a bulk electrolyte solution will produce negligible changes in the concentration of a bulk solution (Refer Fig. 1a). However, if the immediate environment is confined and has limited electrolyte with respect to the metal surface area - as would be the case for a crevice, environmentally assisted cracking, or a deep pit - the limited amount of dissolved species produced as a result of anodic dissolution would be adequate to change the chemical composition (i.e. concentration) of the confined solution as shown in Fig. 1a. Should the change in chemical environment be adequately adverse, these primary reaction products will lead to secondary reactions within the confined space, thus accelerating corrosion damage. This research explores the quantitative effect of confinement on chemical reactivity of metals susceptible to pitting and stress corrosion cracking (SCC).
To investigate the effects of confinement, a simulated crevice was created by maintaining a tight spacing between the polished surface of a flat pH probe and the metal test specimen, as shown in Fig. 1b. The pH probe and the solution are held against the sample by an inert polyethylene fixture. Sensitized AA5083 was chosen as the test material because of its susceptibility to SCC as a result of intergranular precipitates of Al2Mg3 known as β-phase. The electrolyte was pH neutral 0.1 M sodium chloride solution.
Exposing AA5083 to neutral-pH NaCl solution under confinement in free corrosion conditions triggered a spontaneous localized alkaline corrosion, which resulted in a gradual evolution of the pH from 6.9 to roughly 9. At this higher pH value, the passivation film was damaged and hydrogen evolution that promotes the increase in pH was observed as the counter-reaction to aluminum oxidation. This research presents the effect of different ratios of metal surface area to electrolyte volume on the reaction kinetics, as characterized by the evolution of the solution pH with time. Surface area to volume ratios ranged from 4 cm2/ml to 100 cm2/ml. The results are supported with microscopic analysis and EIS studies.

Figure 1
High Resolution in Situ Studies of Localized and Crevice Corrosion with Multiple Beam Interferometry and Atomic Force Microscopy
Authors: Shrestha Buddha Ratna , Bashir Asif , Ankah Genesis Ngwa , Renner Frank , Valtiner Markus 
Published: February 2020

Crevice corrosion (CC) and localized corrosion of metals remains a serious concern for structural materials. Yet both, a real-time and in-situ visualization of (1) initiation of localized corrosion, and (2) corrosion within confined geometries, remains very challenging. In this contribution, we will discuss how multiple-beam interferometry (MBI) can be utilized to directly visualize corrosion processes in real-time and with Ångstrom resolution within well-defined confinement geometries[1]. Also, we will discuss how electrochemical AFM can be utilized to study localized phenomena such as dealloying on patterned surfaces[2]. We will particularly aim to discuss and describe techniques and electrochemical cells, that we recently developed and will discuss how they may become useful in the field of corrosion and localized corrosion.
With MBI, we can detect and track active sites of aluminum corrosion in NaCl solution within confined geometries[3]. We find that CC of aluminum randomly initiates in the confined crevice mouth, where the distance between apposing surfaces is between 20-300 nm. We can directly track oxide dissolution/formation, and corrosion-rates as well as their retardation due to sodium vanadate inhibitors present in solution. Formation of a compacted oxide layer effectively inhibits CC in 5 mM NaCl solutions with 2.5 mM of added NaVO3, while inhibition rapidly breaks down at chloride concentrations above 50 mM. Breakdown of the inhibition-layers is initiated by rapid dissolution of the protective oxide within the confined zone.
With our newly developed electrochemical AFM cell we can accurately track localized initiation sites of corrosion in model de-alloying experiments on patterned surfaces with nm resolution in x/y and atomic resolution in vertical directions[4]. The time resolution of our EC-AFM is currently limited to about 10 seconds per frame. In both parts of this contribution we will discuss experiments with model systems and we aim to specifically focus on technical hurdles and pros/cons of our techniques, including an outlook into what may be achieved in the future.

References:

[1] M. Valtiner, X. Banquy, K. Kristiansen, G. W. Greene, J. N. Israelachvili, Langmuir 2012, 28, 13080.
[2] M. Valtiner, G. N. Ankah, A. Bashir, F. U. Renner, Review of Scientific Instruments 2011, 82, 023703.
[3] B. R. Shrestha, Q. Hu, T. Baimpos, K. Kristiansen, J. N. Israelachvili, M. Valtiner, Journal of the Electrochemical Society 162(7), 2015, C327.
[4] B. R. Shrestha, A. Bashir, M. Valtiner, F. U. Renner, Faraday Discussion - Corrosion 2015, in press.
Nanoporous Silicon-Based Platforms for Biological Applications Fabricated by UV Laser Techniques
Authors: Recio-Sanchez Gonzalo , Pelaez Ramon J , Afonso Carmen N. , Vega Fidel , Martin-Palma Raul J 
Published: February 2020

Nanostructured porous silicon (nanoPS) can be regarded as a complex network of silicon nanocrystals embedded in a porous matrix. NanoPS is fabricated by the electrochemical etch of silicon wafers in HF-based solutions. When crystalline Si is transformed into nanoPS, its intrinsic properties are altered owing to quantum confinement effects. That makes nanoPS an excellent candidate for the development of several applications in a broad range of fields including optoelectronics, photonics, and biomedicine.
Surface micro- and nano-patterning is becoming an important way to enhance the performance of materials. In particular, nanoPS patterns have been proposed for the fabrication of photonic devices, high-sensitivity sensors, etc. Different techniques have been used for the fabrication of patterns on nanoPS including microstructuring the crystalline silicon substrate before the electrochemical etching process, dry soft lithography, stamp pressing, etc. However, none of these methods has the capability to offer flex-ibility in the pattern design in a time-efficient process, in large areas, and in a single step pro-cess.
The present work reports on the fabrication of one- and two-dimensional platforms on nanoPS by phase-mask UV laser interference. This technique is a single-step and flexible approach to produce a large variety of patterns formed by alternate regions of almost untransformed nanoPS and regions where its surface has melted and transformed into Si nanoparticles.
By changing the main experimental parameters such as nanoPS layer porosity, average pore size, laser fluence or pattern period, the properties of the resulting structures can be controlled. These patterns have been proved to be good candidates for such applications as sensing and for the development of biological platforms.
Response Simulation and Extraction of Gas Concentrations for Nanostructure Decorated Nano-/Microporous Silicon Interfaces
Authors: Laminack William , Baker Caitlin , Gole James L. 
Published: February 2020

Sensor and microreactor technology plays a major role in the detection, monitoring, and transformation of materials at interfaces. We study the dynamics of a matrix of reversible interactions of gas analytes with the majority charge carriers of nanostructure modified extrinsic semiconductor interfaces. Nanostructures are deposited on highly sensitive surface layers, created by forming an array of nanopore-coated micropores on p- or n- type silicon semiconductors. The balance of physisorption and chemisorption of the interacting gas analyte on the porous silicon interface is achieved by following the tenants of the developing inverse hard and soft acid/base (IHSAB) interaction model to select metal oxide nanostructures for deposition. These electronically independent metal oxide catalyst sites are readily modified through in-situ nitridation and sulfidation to create a broad sensing matrix. The resulting relative sensor responses of the modified interfaces to gas analytes are explained by the IHSAB interaction model, rather than simply by a shift in system basicity. This expanded matrix of observed sensitivities can then be used to predict the relative response of the interface to a variety of gas phase analytes, as well as direct the choice of porous silicon interface modification for enhanced reversible chemical sensing and electron transduction, in the absence of significant chemical bond formation. The characterization of multiple gas detection, under the guiding model of the IHSAB concept, describes the synergism of two or more analytes simultaneously interacting with an extrinsic semiconductor interface. We are now extending the application of the porous silicon sensors to the identification of organic solvents by measuring impedance. Through the use of an equivalent circuit model, we can explore the physical changes of the porous silicon sensor after metal oxide nanostructure depositions and exposure to various organic solvents.
Critical BEOL Aspects of the Fabrication of a Thermally-Assisted MRAM Device
Authors: O'Sullivan E. J. , Edelstein Daniel , Marchack Nathan , Lofaro Michael , Gaidis Michael , Joseph Eric , Annunziata Anthony , Pfeiffer Dirk , Trouilloud P. L. , Zhu Yu , Holmes Steve , Galan Armand , Pyzna Adam M. , Gonsalves Jemima 
Published: February 2020

Recent developments in new switching methods, such as spin transfer torque [1] and temperature-assisted switching (TAS) [2], have greatly increased interest in MRAM. MRAM fabrication is challenging, however, due to the lack of magnetic materials processing experience by semiconductor lines.
In this talk, we will discuss key back-end-of-line (BEOL) fabrication aspects for a CMOS-integrated thermally-assisted (TAS) MRAM on 200 mm wafers with, e.g., opens/shorts yields of 100% and 99% for 1Mb and 16 Mb arrays, resp. The cell sizes were 33F^2 for the 16M cell, and 73F^2 for the 1M cell, where F = 90 nm. This was achieved in our Microelectronics Research Laboratory (MRL) facility through careful process optimization and adherence to good BEOL processing practice. Factors influencing opens and shorts yields will be discussed.
In the TAS-MRAM magnetic tunnel junction (MTJ) device, data retention is enhanced through synthetic antiferromagnetic exchange coupling; during writing; coupling is overcome through passage of a heating current through the MTJ, and a lower switching field suffices to switch the heated device [2].
Figure 1 contains TEMs of a TAS MRAM structure with two dual-Damascene Cu levels and an Al level after the MTJ. The 90 nm base FEOL/BEOL CMOS technology wafers were fabricated by a third party. Fabrication at IBM commenced at V3, and trilayer via and trench RIE masking schemes were used below the final Al level. The field line (M4) had ferromagnetic (FM) cladding of either PVD Ni-Fe alloy or Co. Cladding proved challenging for narrow field lines (≤ 0.5 µm); e.g., in the initial stages of Cu plating, imperfect corner seedlayer coverage led to solution attack of the Co.
A Damascene TaN layer (ca. 50 nm thick) served as the pedestal for the MTJ. The MTJ resist mask patterns were trimmed using RIE to afford, after MTJ methanol-based RIE etching, final device sizes of about 110 nm. After MTJ encapsulation with SiN and dielectric deposition, V4 vias were RIE etched, stopping on SiN. During M5 dielectric RIE, the MTJ pillar tops were exposed, and the V4 vias’ SiN cleared. The final V5/M6 Cu level was followed by an Al level.
Besides the FM liner, other processing challenges included clearing isolated vias, and developing a robust trench RIE process to contact the MTJs.
[1] J. C. Slonczewski, J. Magn. Magn. Mater.,159, L1 (1996).
[2] For example, I. L. Prejbeanu et al., J. Phys: Condens. Matter, 19 (16), 165218 (2007).

Acknowledgements: Back-end-of-line fabrication was carried out in the Microelectronics Research Laboratory (MRL) at the T. J. Watson Research Center. The MRAM stacks were deposited at Crocus Technology in Grenoble, France.

Figure 1
Flexible Ultra-Thin Silicon Solar-Cell Implemented with Energy-Down-Shift Via Cd0.5Zn0.5s/ZnS Core/Shell Quantum Dots
Authors: Park Jin-Seong , Shim Jae-Hyoung , Ko Yun-Hyuk , Park Joo-Hyeong , Lee Gon-Sub , Park Jea-Gun 
Published: February 2020

For the past few decades, flexible or bendable silicon, dye-sensitized, organic, and hybrid solar-cells have been intensively researched to improve power-conversion-efficiency (PCE) and to minimize the fabrication cost because of their attractive applications such as building-integrated photovoltaic (BIPV), and portable electronics power. Although flexible or bendable dye-sensitized, organic, and hybrid solar-cells have demonstrated a relevant PCE and solar-cell fabrication cost for a real photovoltaic application, their PCE and solar-cell fabrication cost was still quite higher than that of solid silicon solar-cells. Recently, S. Jeong et al. reported ultra-thin silicon (~10-um in thickness) solar-cell showing a maximum PCE of 13.7 %. However, it was fabricated with typical high-cost semiconductor processes such as SOI wafer, photolithograph, and deep reactive-ion etching (RIE). In addition, it could not demonstrate flexible or bendable solar-cell characteristics.
We, therefore, developed a flexible ultra-thin silicon solar-cell implemented with energy-down-shift layer via Cd0.5Zn0.5S/ZnS core/shell quantum-dots (QDs). In particular, in order to achieve a low cost solar-cell fabrication, we introduced ultra-thinning process (~30-um in thickness) via KOH etching, back-surface-filed (BSF) formation via thin Al-film evaporation and rapid-thermal annealing (RTA), top electrode patterning via thin film Ag evaporation, and spin-coating of core/shell QDs. In addition, in order to enhance an external quantum efficiency (EQE) at ultra-violet (UV) wavelength region, we implemented energy-down-shift layer by coating Cd0.5Zn0.5S/ZnS core/shell QDs on flexible ultra-thin silicon solar-cells.
It was observed that flexible ultra-thin (~30-um in thickness) silicon solar-cells implemented with energy-down-shift layer showed stable flexible and twistable characteristics as shown in Fig. 1. In addition, Fig. 2 presents the EQE as function of wavelength and current density vs. voltage characteristics. It was confirmed that the Cd0.5Zn0.5S/ZnS core/shell QDs on the flexible ultra-thin solar-cells enhanced the EQE of about 17 %P at the UV light region (300 – 400 nm) as shown in Fig. 2(a). In particular, the QDs enhanced the PCE to 0.77%P by the energy-down-shift effect that enhanced the EQE, which resulting in that the PCE of the ultra-thin silicon solar-cells was about 12.37 %.
In the conference, we will present in detail physical, optical electrical, and flexible properties of flexible ultra-thin silicon solar-cells implemented with energy-down-shift layer. In particular, we will report how their PCE can be sustained after the bending cycles of 5,000.
* This work was financially supported by the Brain Korea 21 Plus Program in 2015.

Reference

[1] DH Lee, JY Kwon, and S Maldonado Nano letters 14
(4), 1961-1967(2014)
[2] S Wang, BD Weil, and Y Li, Nano letters, 13 (9), 4393-4398 (2013)

Figure 1
PTB7:PC71BM Bulk Heterojunction Solar Cells with Multiple Additives
Authors: Ohzeki Masaya , Qiu Jiayu , Fujii Shunjiro , Kataura Hiromichi , Nishioka Yasushiro 
Published: February 2020

Bulk-hetero junction organic solar cells with active layers based on [4,8-biz[Poly[[4,8-bis[(2-ethylhexyl)oxy]benzo [1,2-b:4,5-b']dithiophene-2,6-diyl]　[3-fluoro-2-[(2-ethylhexyl)carbonyl]thieno[3,4-b]-thiophenediyl] and phenyl-C71-butyric-acid-methyl-ester (PC71BM) with an additive of diiodooctane (DIO) has attracted a lot of attentions due to their high power conversion efficiencies over 9% [1]. The addition of DIO significantly improved the solar cell performance, which was considered due to the change of the nano-structure configulations by the introduction of DIO. On the other hand, the introduction of dimethyl sulfoxide　(DMSO) into the dicholobenzen solution of PTB7:PC71BM used to deposit the active layers [2]. However, the influence of the DMSO introduction into the PTB7:PC71BM:DIO systems have not yet been reported to the best of our knowledge.
In this work, active layers were fabricated by spin coating 1,2-dichlorobenzene (500 μl) solutions of PTB7 (5 mg): PC71BM (7.5 mg) containing 0.369 mg (3wt%) of DIO and additional DMSO with different weight ratios to the total weight of PTB7:PC71BM (12.5 mg) from 0 to 30 wt% (0 to 3.69 mg). It was found that the solar cells with 13wt% (1.60 mg) of DMSO additives exhibited the best solar cell performance of an open circuit voltage of 0.72 V, short circuit current density of 15.63 mA/cm2, fill factor of 0.49, and power conversion efficiency of 5.47%. The significant structural changes were found from the surface morphology observations of the active layers depending on the DMSO concentration as observed by atomic force microscope.
[1] Z. He et al., Nat Photonics 6, (2012) 591.
[2] Chu et al., Appl. Phys. Lett. 98, (2011) 253301.
(Invited) Fabrication of N-Polar (Al,Ga,In)N Heterostructures for Transistor Applications
Authors: Keller Stacia , Mishra Umesh K 
Published: February 2020

This presentation will address the growth of N-polar (000-1) (Al,Ga,In)N/GaN heterostructures by metal-organic chemical vapor deposition (MOCVD) with emphasis on transistor applications. While the N-polar growth direction is in particular advantageous for highly scaled devices operating at frequencies of 30GHz and beyond, results for high power transistors working at lower frequencies will be discussed as well. Differences in the MOCVD growth of N-polar in comparison to metal-polar heterostructures will be described. Prerequisites for the fabrication of high quality (Al,Ga,In)N were the use of misoriented substrates in combination with a careful process optimization.