bluuebunny/crossref_metadata_2025 huggingface dataset:
Role of gravity in particle physics: A unified approach
Authors: Alvarez Pedro D. , Valenzuela Mauricio , Zanelli Jorge
Published: May 2020

General Relativity (GR) and the Standard Model (SM) of particle physics are two enormously successful frameworks for our understanding the fundamental laws of nature. However, these theoretical schemes are widely disconnected, logically independent and unrelated in scope. Yet, GR and SM at some point must intersect, producing claims about phenomena that should be reconciled. Be it as it may, both schemes share a common basic ground: symmetry under local Lorentz transformations. Here, we will focus on the consequences of assuming this feature from the beginning to combine geometry, matter fields and gauge interactions. We give a rough description of how this could be instrumental for the construction of a unified scheme of gravitation and particle physics.
Solar system tests of a new class of f(z) theory
Authors: Wang Ji-Yao , Feng Chao-Jun , Zhai Xiang-Hua , Li Xin-Zhou
Published: May 2020

Recently, a new kind of [Formula: see text] theory is proposed to provide a different perspective for the development of reliable alternative models of gravity in which the [Formula: see text] Lagrangian terms are reformulated as polynomial parametrizations [Formula: see text]. In the previous study, the parameters in the [Formula: see text] models have been constrained by using cosmological data. In this paper, these models will be tested by the observations in the solar system. After solving the Ricci scalar as a function of the redshift, one could obtain [Formula: see text] that could be used to calculate the standard Parametrized-Post-Newtonian (PPN) parameters. First, we fit the parametric models with the latest cosmological observational data. Then, the tests are performed by solar system observations. And last we combine the constraints of solar system and cosmology together and reconstruct the [Formula: see text] actions of the [Formula: see text] parametric models.
Simple reflexive modules over finite-dimensional algebras
Authors: Ringel Claus Michael
Published: May 2020

Let [Formula: see text] be a finite-dimensional algebra. If [Formula: see text] is self-injective, then all modules are reflexive. Marczinzik recently has asked whether [Formula: see text] has to be self-injective in case all the simple modules are reflexive. Here, we exhibit an 8-dimensional algebra which is not self-injective, but such that all simple modules are reflexive (actually, for this example, the simple modules are the only non-projective indecomposable modules which are reflexive). In addition, we present some properties of simple reflexive modules in general. Marczinzik had motivated his question by providing large classes [Formula: see text] of algebras such that any algebra in [Formula: see text] which is not self-injective has simple modules which are not reflexive. However, as it turns out, most of these classes have the property that any algebra in [Formula: see text] which is not self-injective has simple modules which are not even torsionless.
Quantum synchronization and correlations of two qutrits in a non-Markovian bath
Authors: Zhang Jian-Song
Published: May 2020

We investigate quantum synchronization and correlations of two qutrits in one non-Markovian environment using the hierarchy equation method. There is no direct interaction between two qutrits and each qutrit interacts with the same non-Markovian environment. The influence of the temperature of the bath, correlation time and coupling strength between qutrits and bath on the quantum synchronization and correlations of two qutrits are studied without the Markovian, Born and rotating wave approximations. We also discuss the influence of dissipation and dephasing on the synchronization of two qutrits. In the presence of dissipation, the phase locking between two qutrits without any direct interaction can be achieved when each qutrit interacts with the common bath. Two qutrits within one common bath cannot be syncrhonized in the purely dephasing case. In addition, the Arnold tongue can be significantly broadened by decreasing the correlation time of two qutrits and bath. Markovian baths are more suitable for synchronizing qutrits than non-Markovian baths.
Harnessing Supply Chain Knowledge for Mitigating the Negative Effects of Bricolage
Authors: Sahi Gurjeet Kaur , Agarwal Nivedita
Published: May 2020

Bricolage is a term used to illustrate the practice in which small firms tap scant available resources to exploit business opportunities and to facilitate innovation. We focus on decreasing returns from excessive bricolage and, more importantly, highlight an important role played by supply chain knowledge in mitigating decreasing returns from bricolage. The role played by supply chain knowledge in reducing the negative effects of excessive bricolage is not explored yet. This study, in the context of an emerging economy, seeks to isolate the linear and quadratic effects of bricolage on firm performance and examines the moderating influence of supply chain knowledge on the bricolage-to-firm performance relationship. To test the proposed relationships, data from large-scale manufacturing firms in north-west India were used. The final sample size of 106 firms was used for testing the relationships using stepwise OLS analysis. The results revealed that at lower levels of supply chain knowledge, bricolage had an inverted-U relationship with firm performance. In other words, supply chain knowledge mitigates the negative effects of bricolage on performance. However, it did not strengthen the positive effect of bricolage on performance.
The Diophantine equation Fn = P(x)
Authors: Tengely Szabolcs , Ulas Maciej
Published: May 2020

We consider equations of the form [Formula: see text], where [Formula: see text] is a polynomial with integral coefficients and [Formula: see text] is the [Formula: see text]th Fibonacci number that is, [Formula: see text] and [Formula: see text] for [Formula: see text] In particular, for each [Formula: see text], we prove the existence of a polynomial [Formula: see text] of degree [Formula: see text] such that the Diophantine equation [Formula: see text] has infinitely many solutions in positive integers [Formula: see text]. Moreover, we present results of our numerical search concerning the existence of even degree polynomials representing many Fibonacci numbers. We also determine all integral solutions [Formula: see text] of the Diophantine equations [Formula: see text] for [Formula: see text] and [Formula: see text].
REMITTANCES, INSTITUTIONS AND FINANCIAL INCLUSION: NEW EVIDENCE OF NON-LINEARITY
Authors: ISSABAYEV MURAT , SAYDALIYEV HAYOTBEK , AVSAR VEYSEL , CHIN LEE
Published: May 2020

This paper investigates the effect of remittance inflows on financial inclusion. Using data from high remittance-receiving developing countries and applying dynamic panel data methods, we find that remittance inflow has a negative impact on financial inclusion for countries with low level of remittances. However, this relationship is positive for countries with high level of remittances. Our study found that there exists a nonlinear relationship between remittances and financial inclusion. We also show that the effect of remittances on the financial inclusion is conditional upon people’s perception about institutions.
Origins and Immunity Networking Functions of EDS1 Family Proteins
Authors: Lapin Dmitry , Bhandari Deepak D. , Parker Jane E.
Published: May 2020

The EDS1 family of structurally unique lipase-like proteins EDS1, SAG101, and PAD4 evolved in seed plants, on top of existing phytohormone and nucleotide-binding–leucine-rich-repeat (NLR) networks, to regulate immunity pathways against host-adapted biotrophic pathogens. Exclusive heterodimers between EDS1 and SAG101 or PAD4 create essential surfaces for resistance signaling. Phylogenomic information, together with functional studies in Arabidopsis and tobacco, identify a coevolved module between the EDS1–SAG101 heterodimer and coiled-coil (CC) HET-S and LOP-B (CCHELO) domain helper NLRs that is recruited by intracellular Toll-interleukin1-receptor (TIR) domain NLR receptors to confer host cell death and pathogen immunity. EDS1–PAD4 heterodimers have a different and broader activity in basal immunity that transcriptionally reinforces local and systemic defenses triggered by various NLRs. Here, we consider EDS1 family protein functions across seed plant lineages in the context of networking with receptor and helper NLRs and downstream resistance machineries. The different modes of action and pathway connectivities of EDS1 family members go some way to explaining their central role in biotic stress resilience.
Class Position and Political Opinion in Rich Democracies
Authors: Lindh Arvid , McCall Leslie
Published: May 2020

In many high-income countries today, scholarly interest in the politics of class has coincided with growing economic inequality, rising support for nonmainstream political parties and candidates, and increasing flows of immigration. We review social science research on the views of different class segments vis-à-vis economic, political, and sociocultural issues, finding greater scholarly attention to the interdependence of economic, social, and political concerns and preferences than arguably was the case even a few years ago. Our main aim is to synthesize and critically evaluate this rapidly expanding literature, but we also provide empirical data on class differences and similarities in political opinion across 18 countries, and we pinpoint several areas of research that are in need of further empirical, methodological, and theoretical inquiry.
The Longitudinal Revolution: Sociological Research at the 50-Year Milestone of the Panel Study of Income Dynamics
Authors: Pfeffer Fabian T. , Fomby Paula , Insolera Noura
Published: May 2020

The US Panel Study of Income Dynamics (PSID) celebrated its 50th anniversary in 2018. Initially designed to assess the nation's progress in combatting poverty, PSID's scope broadened quickly to a variety of topics and fields of inquiry. To date, sociologists are the second-most frequent users of PSID data after economists. Here, we describe the ways in which PSID's history reflects shifts in social science scholarship and funding priorities over half a century; take stock of the most important sociological breakthroughs it facilitated, in particular those relying on the longitudinal structure of the data; and critically assess the unique advantages and limitations of PSID and surveys like it for today's sociological scholarship.
Initial Step of Virus Entry: Virion Binding to Cell-Surface Glycans
Authors: Koehler Melanie , Delguste Martin , Sieben Christian , Gillet Laurent , Alsteens David
Published: May 2020

Virus infection is an intricate process that requires the concerted action of both viral and host cell components. Entry of viruses into cells is initiated by interactions between viral proteins and cell-surface receptors. Various cell-surface glycans function as initial, usually low-affinity attachment factors, providing a first anchor of the virus to the cell surface, and further facilitate high-affinity binding to virus-specific cell-surface receptors, while other glycans function as specific entry receptors themselves. It is now possible to rapidly identify specific glycan receptors using different techniques, define atomic-level structures of virus-glycan complexes, and study these interactions at the single-virion level. This review provides a detailed overview of the role of glycans in viral infection and highlights experimental approaches to study virus-glycan binding along with specific examples. In particular, we highlight the development of the atomic force microscope to investigate interactions with glycans at the single-virion level directly on living mammalian cells, which offers new perspectives to better understand virus-glycan interactions in physiologically relevant conditions.
Determining Proton Transport in Pseudo Catalyst Layers Using Hydrogen Pump DC and AC Techniques
Authors: Sabarirajan Dinesh C. , Liu Jiangjin , Qi Yongzhen , Perego Andrea , Haug Andrew T. , Zenyuk Iryna V.
Published: May 2020

Optimizing electrode morphology with a more uniform ionomer distribution is key to reducing ohmic losses and increasing electrocatalyst utilization in polymer electrolyte fuel cells (PEFCs). Inherent ionomer conductivity, volume fraction and tortuosity determine effective ionic conductivity. We use hydrogen pump (HP) method to measure effective ionic conductivity of a pseudo catalyst layer (PCL) comprised of Vulcan XC-72 carbon black and 3M 825 EW ionomer with ionomer to carbon (I/C) ratios of 0.6, 1 and 1.4 and relative humidity (RH) range of 50 to 120%. These direct current (DC) experiments are then compared with electrochemical impedance spectroscopy (EIS). Both DC and EIS methods show good agreement, indicating that EIS can be used as an alternative to DC method in HP experiment. Ionic conductivity for PCL with I/C of 1 and 1.4 was found to be about one order of magnitude higher than I/C of 0.6 for most of the RH range. At 90% RH tortuosities for I/C = 1 and 1.4 were close to 1, whereas tortuosity for I/C = 0.6 was 3. With decrease in relative humidity tortuosities increased linearly and at 50% relative humidity a PCL with I/C = 0.6 had the highest tortuosity of 6.1.
(Invited) Wafer-Scale Epitaxy of Transition Metal Dichalcogenides By MOCVD
Authors: Choudhury Tanushree , Chubarov Mikhail , Zhang Xiaotian , Redwing Joan M.
Published: May 2020

Monolayer semiconducting transition metal dichalcogenides (MX2, M=W, Mo and X=S, Se) exhibit novel electronic and optical properties. Availability of epitaxial single-crystal monolayers over a wafer scale is a major hurdle in integrating these materials with existing device fabrication processes. Our approach focusses on synthesis of these monolayers using gas source precursors, like those used in traditional III-V semiconductor industry. The precursors are kept in temperature and pressure-controlled bubblers outside the growth chamber and can be metered independently into the growth zone with precision. Uniform epitaxial binary TMD monolayers including MoS2, WS2, WSe2 and MoSe2 have been deposited on 2” sapphire wafers in a cold-wall CVD reactor using metal hexacarbonyl and hydride chalcogen precursors. A multi-step growth process comprising of precursor modulation was developed for WSe2 to independently control nucleation density and the lateral growth rate of monolayer domains on the sapphire substrate [1]. For the sulfides, additional temperature modulation was introduced to increase crystalline quality. Using this approach, uniform, coalesced monolayer and few-layer TMD films were obtained on 2” sapphire substrates. In-plane X-ray diffraction demonstrates that the films are epitaxially oriented with respect to sapphire with narrow X-ray full-width-at-half-maximum indicating minimal rotational misorientation of domains within the basal plane [2]. Deposition of these materials in the same reactor provides insight into the factors controlling their growth, which in essential for the growth of heterostructures and/or alloys. Transmission electron microscopy analysis of these materials revealed additional information about the coalesced film structure. For instance, ~95 % single oriented WS2 domains were observed when the film growth rate was modulated. For WS2, it was also confirmed that despite translational line defects present in the film, mirror boundaries were predominantly absent. WS2 also showed no defect related photoluminescence peak at 80 K, indicating its high quality.

In this talk the factors affecting the growth of TMDs (MX2, M=W, Mo and X=S, Se) will be presented. The role of the substrate surface in the nucleation and growth of these TMDs will be discussed. In addition, the structural and optoelectronic characteristics for these films will also be presented.

The authors acknowledge financial support of the U.S. National Science Foundation through the Penn State 2D Crystal Consortium – Materials Innovation Platform (2DCC-MIP) under NSF cooperative agreement DMR-1539916 and EFRI 2-DARE Grant EFRI-1433378.

[1] Zhang X, Choudhury TH, Chubarov M et al., 2018. Nano Lett. 18(2):1049–56

[2] Chubarov M, Choudhury TH, Zhang X et al., 2018. Nanotechnology. 29(5):55706
(Invited) Seeing 2D Sheets with Fluorescence Quenching Microscopy
Authors: Huang Jiaxing
Published: May 2020

Fluorescence quenching microscopy (FQM) was initially developed for high throughput imaging of graphene based sheets on arbitrary substrates under a common fluorescence microscopy. It takes advantages of the long range, energy transfer-based fluorescence quenching effect of graphene-based materials, and can obtain images with high contrast and high layer resolution comparable to those of scanning electron microscopy (SEM) and atomic force microscopy (AFM). FQM was later applied to image other strongly quenching sheets such as transitional metal dichalcogenides.

The high-contrast optical imaging of nearly transparent 2D materials such as clays and some oxides sheets has been an outstanding challenge; yet it is a critical research capability needed in the synthesis and processing of these materials, which have shown promise in a number of applications including barrier coatings, membranes, and composites. Using delaminated silicate clay and titania sheets as model system, here we show that these weakly quenching, nearly transparent 2D sheets can also be readily imaged by FQM based on a new mechanism with SEM and AFM level of contrast and layer resolutions. When different 2D materials are co-deposited, FQM not only differentiates them readily based on their quenching capabilities, but also can resolve their vertical stacking sequence based on the contrast of their overlapped areas.
(Invited) Impact of Substrates and Interfaces on 2D TMDC Properties
Authors: Leonhardt Alessandra , Koladi Mootheri Vivek , Lockhart de la Rosa Cesar Javier , Nuytten Thomas , Mascaro Marco , Sergeant Stefanie , Banszerus Luca , Stampfer Christoph , Lin D , Huyghebaert Cedric , De Gendt Stefan
Published: May 2020

2D TMDCs show promise to multiple applications, from distributed systems, to optical devices, and high-performance electronics. Nonetheless, how these ultra-thin semiconductors are impacted by their encapsulating environment / interfacial interactions is still a matter of discussion. Challenges relate to how to characterize dielectric surface related interactions, and how to assess the interface quality (quickly and in-line). We will discuss the impact of substrates / interfaces on electrical and optical properties of TMDCs and identify which parameters are the main affecting factors.

We show that defect bands from the dielectric substrate can result in doping or in loss of ambipolarity, depending on their position relative to the band gap of the 2D TMDC. From correlations between AFM and Raman maps, we show that nanoscale strain and doping are closely linked, which is confirmed by conductive AFM measurements. To assess substrate defectivity and the impact of trapped species, we demonstrate a novel and simple method, which relies on indirect band gap transitions.

Finally, we demonstrate that by understanding the multiple mechanisms of Fermi level pinning and controlling both contact and dielectric interface, ambipolarity can be demonstrated in MoS2 flakes.
Analysis of the Impact of Fast Charging on Aging for Smartphone Cells: A Case Study Using Synchrotron Based Techniques
Authors: Besli Muenir Mustafa , Subbaraman Anantharaman , Ramezan Pour Safaei Farshad , Metzger Michael , Ravi Nikhil , Johnston Christina , Christensen Jake , Kuppan Saravanan
Published: May 2020

With the rapid market increase of consumer electronic devices such as smartphones and tablets, the performance of lithium-ion batteries in such devices becomes an important factor. In particular, fast charging, longer lasting batteries and safety are primary concerns for consumers. Lithium cobalt oxide (LCO) is a common cathode material for these applications, and in smartphone applications with 1-2 cycles a day, LCO has been proven to be a good cathode with its high cycle life.1,2 However, besides offering high cycling stability and power density for mobile consumer applications, another requirement for LIBs utilized in smartphones and other portable electronic devices is the capability of fast charging, without a detrimental impact on the cycling stability. Different fast charging profiles can lead to various extents of degradation within the full cell. Consequently, strategies are needed to avoid or mitigate any negative impact of fast charging on battery capacity, power degradation and cycle life.

In this work, we employed extensive synchrotron-based characterization methods on smartphone batteries (LCO/graphite), offering new insight into the various degradation mechanisms during fast charging. Specifically we focus on an in-house developed fast-charging profile based on a physics-based battery model and compare it with the fast charging profile provided by the OEM. We reveal how lithium plating occurring on the anode side during fast charging is ‘mirrored’ on the cathode side leading to inactive cathode areas that only participate partly in lithium intercalation. While no morphological changes were observed in the cathode opposing the plating sides on the anode, in-situ hard XAS spectroscopy shows that deactivated spots on the cathode are not as redox active anymore, and synchrotron micro XRD shows significant changes in the lattice d-spacing value. Further, we use micro XRF to map the Co content in different regions of the anode, which stems from cathode transition metal dissolution. Finally, we conclude that a fast charging strategy derived from a physics-based model drastically reduces capacity fade and rate of impedance rise in a LCO/graphite smartphone cell as used in this work.

References

1 L. Wang, J. Ma, C. Wang, X. Yu, R. Liu, F. Jiang, X. Sun, A. Du, X. Zhou and G. Cui, Adv. Sci., 2019, 6, 1900355.

2 M. S. Whittingham, Chem. Rev., 2004, 104, 4271–4302.
(Invited) Polaron Mediated Cooling Dynamics in Perovskite Materials: Effect of Temperature
Authors: Ghosh Hirendra Nath
Published: May 2020

During last decade huge number of research investigations are going on different kind of halide perovskite materials due to their exciting optoelectronic properties which includes ability to provide very efficient solar devices. Charge carrier cooling process is one of the key process for design and development of any higher efficient optoelectronic devices. Ultrafast hot carrier cooling is the key loss channel which limits achievable solar conversion efficiency. Delaying the carrier cooling high efficient hot-carrier solar cell can be realized. Thus, delayed hot carrier cooling in the cell absorber layer can make hot carrier extraction a relatively easier task, assisting in the realization of hot carrier solar cells. There have been plentitude of reports concerning the slow carrier cooling in perovskite materials, which has eventually triggered interest in the radical understanding of the native photophysics driving the device design. In our recent investigation, we have demonstrated dramatic dip in the cooling rate in CsPbBr3 NC after growing Cs4PbBr6 shell over it, in contrast to the bare CsPbBr3 core NCs. By employing ultrafast transient absorption spectroscopy, we have investigated the disparity in the hot carrier thermalization pathways in the CsPbBr3 and CsPbBr3@Cs4PbBr6 core-shell NCs under same laser fluence, which can be validated as a corollary of polaron formation in the later NCs. Role of phonon in the cooling process has also been investigated by carrying out the ultrafast transient studies in the temperature range of 5K-300K.

References

1. G. Kaur, K. J. Babu, N. Ghorai,T. Goswami, S. Maiti, and H. N. Ghosh J.
Phys. Chem. Lett, 2019, 10, 5302.
Towards Lead-Free Perovskite Solar Cells: Hurdles and Prospects
Authors: Obaseki Oluwatosin Samuel , Samsuri Siti Azrah , Pakhuruddin Mohd Zamir , Rashid Marzaini , Hashim Mohd Roslan
Published: May 2020

Consistent increase in the power conversion efficiency (PCE) of lead-based halide perovskite solar cells (PSCs) has been observed over the past one decade. PCE is currently slightly above 25 %. Various components within PSC devices are responsible for cell performance, however the most important component is the perovskite layer. Lead (Pb) has taken the lead in the achievement of impressive PCEs of PSCs; Pb has been a major part of the perovskite structure because of its excellent optoelectronic properties. Pb is however known to be toxic, with irreversible detrimental consequences upon human exposure. Plying less expensive routes such as solution process techniques in obtaining direct current electricity through photovoltaics is considered a huge advancement in photovoltaic technology; nevertheless, technological advancement should not be detrimental to health. Here, we provide up-to-date highlights on major progresses made towards achieving high efficiency in the fabrication of lead-free perovskites for photovoltaics application and hence make considerable suggestions on ways forward.
Vapor-Phase Dehydrogenative Synthesis of Polycyclic Aromatic Hydrocarbons for Garment-Integrated Solar Cells
Authors: Bilger David , Park Kwang-Won , Andrew Trisha L.
Published: May 2020

Polycyclic aromatic hydrocarbons (PAHs) are compelling candidates for optoelectronic and spintronic devices due to their unique condensed phase electronic structures and potential for ambipolar charge transport. Unfortunately, most PAHs exhibit poor film forming properties that constrain their technological potential. While on-surface synthesis has been used to simultaneously synthesize and deposit monolayers of such compounds, this technique necessitates high temperatures, ultrahigh vacuums, and oriented metal surfaces that limit the practical synthesis and fabrication of PAH films. Here, a custom built hot-wall reactor is used to deposit higher-order acenaphthofluoranthenes via a vapor phase dehydrogenative synthesis performed under mild temperatures and pressures. This process creates an organic alloy of various fluoranthenes with differing extended pi-cores. The films can be deposited over any inert substrate, both planar and complex, and are patternable. Further, efficient resonant energy transfer is observed between chemical species within the films. Such properties make these films useful for addressing persistent issues with wearable optoelectronics, including a scarcity of ambipolar materials that are necessary to integrate solar cells with fabrics.

Figure 1
Synthesis of Chiral Carbazole-Based Porphyrins and BODIPYs
Authors: Maeda Chihiro
Published: May 2020

We have explored the synthesis and functionalization of carbazole-based porphyrins and BODIPYs showing NIR absorption and solid-state fluorescence, respectively. Here, we synthesized chiral carbazole-based porphyrins and BODIPYs. The former showed Cotton effect in the NIR region, while the latter showed CPL both in solution and in the solid state. In this presentation, chiroptical properties of these chiral dyes are reported.
Polymerization of Self-Assembled Tetraazaporphyrins
Authors: Tahir M Nazir , Abdulhamied Elmahdy , Nyayachavadi Audithya , Selivanova Mariia , Rondeau-Gagné Simon , Eichhorn S. Holger
Published: May 2020

Polymerization of self-assembled supramolecular structures considerably increases their often limiting thermal and chemical stability, which widens their potential application in commercial products. Particularly interesting for self-assembled materials is the topochemical polymerization of diacetylenes to polydiacetylenes because it can be initiated photochemically and thermally without the need for additives, it proceeds with minimal structural changes, and it generates new functionality since polydiacetylene is a 1-dimensional organic semiconductor and absorbs visible light. Polydiacetylenes have been generated in single crystals, gel phases, thin films, and membranes but their formation in mesophases, such as liquid crystals, has been surprisingly little studied although higher ordered mesophases should support the topochemical polymerization of diacetylenes (1,3-butadiyne groups) and may give access to large domains of uniformly aligned materials. Presented here are tetraazaporphyrins that contain eight alkyl chains with diacetylene groups to probe their mesomorphism and conversion into multifunctional polydiacetylene materials. While incorporation of diacetylene groups supports columnar mesomorphism, successful photopolymerization required the presence of directing amide groups that suppressed columnar in favour of nematic mesomorphism. Still, polymerization of the nematic mesophase generated a soluble nematic polydiacetylene of significantly higher molecular weight (Mn = 77 kDa or 25 monomer units by GPC) than what has been obtained in gel phases of related compounds. Formation of polydiacetylene was confirmed by Raman spectroscopy and its nematic structure was verified by UV-vis spectroscopy, polarized optical microscopy, and X-ray diffraction. Both, its nematic structure and the incorporation of eight side-chains per discotic unit provide the polydiacetylene with sufficient solubility for casting thin films on substrates. AFM studies of films casted onto silicon wafers revealed a grid-like structure of connected nanofibers.
Substituent Effect on Oxidative Dimerization of Porphyrins
Authors: Hiroto Satoru
Published: May 2020

Three-dimensional π-conjugated molecules have received extensive attention in many chemical research areas due to their interesting structure and unique characteristics. In particular, twisted π-conjugated systems have been focused on for potential applications to solution processible organic materials. To date, numerous twisted organic molecules such as twistacenes have been synthesized. Under these situations, we found that oxidation of aromatic amines facilitates construction of twisted π-conjugated molecules. For example, oxidation of beta-amino substituted porphyrins provided three-dimensional porphyrins in excellent yield. Sequential use of amination and oxidation toward 5,10,15,20-tetramesitylporphyrin afforded highly twisted porphyrin oligomers. For this reaction, structures of the dimers proved dependent on the meso-substituents. This time, we investigated the substituent effect on the dimerization reactions. Introduction of more bulky substituents at meso-positions on oxidation process provided the corresponding twisted porphyrin dimers with larger twisted angles. In the case of p-tolyl and other aryl substituents without ortho substituents afforded porphyrin dimers with double spirocyclic linkages. The electrochemical analysis revealed the presence of electronic communications between two porphyrin units for the obtained dimers even through the spirocyclic linkages. The central metal also affects the conformations of the dimers. The central Ni(II) metal can be easily removed by treatment of sulfonic acid. Insertion of Zn(II) and Cu(II) metals reduced the twisted angle of the corresponding dimers mainly due to the planar features of the porphyrin units. The presence of magnetic interactions between two porphyrin units were revealed by temperature dependent magnetic susceptibility measurements on SQUID with Cu(II) analogues. In this presentation, we will disclose the structural characterizations of these dimers and would like to show the relationship between electrochemical properties and the conformations of porphyrin dimers.
Electrochemical Properties of Mono- and Bis-CN Ligated Cobalt Corroles
Authors: Osterloh Ryan , Quesneau Valentin , Desbois Nicolas , Brandes Stéphane , Blondeau-Patissier Virginie , Paolesse Roberto , Gros Claude P. , Kadish Karl M.
Published: May 2020

Corroles have attracted a great deal of attention in terms of application and understanding their electronic configuration, especially the innocence or non-innocence of the macrocyclic ligand. These properties are known to be strongly influenced by the metal ion and degree of axial coordination, namely 4, 5 and 6-coordinate. In addition, these properties are also dependent on the solvent and possibly peripheral substituents. We have previously examined bis-pyridine and mono-DMSO cobalt corroles and in this work describe the electrochemical and spectroscopic properties of newly synthesized series of anionic axially ligated mono-CN and in-situ generated bis-CN cobalt A3-triarylcorroles with a tetrabutylammonium counterion. Examples of the synthesized corroles are shown in the figure and represented as [(Ar)3CorCo(CN)]- where (Ar)3Cor is the corrole macrocycle and Ar is one of several meso-phenyl rings containing electron-withdrawing or electron-donating substituents.

Figure 1
Effects of Sulfates on Corrosion of 430 Ferritic Steel in CO2-Saturated Water Containing Oxygen
Authors: Ziomek-Moroz Margaret , Repukaiti Reyixiati , Doğan Ömer N. , Oleksak Richard P. , Thomas Randal B. , Baltrus John P , Tucker Julie
Published: May 2020

Aqueous corrosion can be an issue for structural materials in direct supercritical CO2 power cycles, especially in low temperature components such as water separators and coolers where aqueous condensation appears as supercritical CO2 working fluid containing impurities (SOx, O2, H2O) cools down. This study aims at testing 430 ferritic steel as a material of construction for the low temperature components. Immersion experiments were carried out in an aqueous solution with and without H2SO4 (pH was 3 and 4, respectively) in an autoclave pressurized to 8 MPa with 99% CO2 and 1% O2 gas mixture. Temperature of each solution was 50°C. Immersion tests lasted up to 500 hours. Post-corrosion surface characterization techniques included X-ray diffraction, scanning electron microscopy and energy dispersive X-ray spectroscopy. The characterization indicated that general corrosion took place in both cases with and without H2SO4. The corrosion rate of samples was calculated based on the mass loss. The corrosion rate values for 430 steel in solutions with and without H2SO4 were very low and similar after 96 hours of immersion. These initial results indicated that the presence of SO4
2- in CO2 -saturated water containing O2 did not have a detrimental effect on the corrosion resistance of 430 steel.
A Revised Model for Electrochemical Frequency Modulation for Corrosion Estimation
Authors: Lalvani Shashi , Ullah Sifat
Published: May 2020

Electrochemical frequency modulation technique allows for evaluation of corrosion rate without prior information of the Tafel parameters. The basic premise of this approach is that since the material degradation can be described by a nonlinear model, the application of an AC perturbation signal will result in the generation of higher harmonics corresponding to the multiples of the original signal frequency. However, the previous research has ignored the following: (i) the effect of the double layer capacitance (Cd) at the surface of the corroding electrode, and (ii) the solution resistance (Rs) on the output signal, which makes the estimation of faradaic current impossible. Thus, the true corrosion rate cannot be calculated.

Our research has shown that when these two effects are taken into account, the output signal displays shift in the higher order harmonics, which is a function of not only the order of the harmonics but also of the Tafel parameters Cd, and Rs. Thus, it becomes possible to calculate the faradaic current and accurately estimate the corrosion rate.
Optimal Anode Potential Range for Electrochemical Synthesis of Struvite from Wastewater
Authors: Sultana Ruhi , Greenlee Lauren Fay
Published: May 2020

Electrochemical recovery of phosphorous and nitrogen from wastewater as struvite (NH4MgPO4.6H2O) is progressively gaining importance as one of the innumerable pathways of sustainable development. However, the optimal range of anode potential that maximizes struvite purity under varied parametric conditions of pH and ion concentrations other than NH4
+and PO4
-3 has not been methodically explored so far. Additionally, corrosion behavior of a sacrificial magnesium anode under an anode potential range needs to be investigated because according to techno-economic feasibility criterion, it is advantageous to produce struvite with minimal consumption of magnesium. In this study, we will report on the effects of pH (4 and 8) and chloride ion concentration (0.1 M to 1 M) on struvite production and magnesium dissolution rates through performing a systematic investigation using Linear Sweep Voltammetry (LSV) and Potentiodynamic Polarization (PDP) techniques. Aqueous solutions of dihydrogen ammonium phosphate with varied chloride ion concentration are used as simulated wastewater. Electrochemical experiments are conducted in batch mode with a sacrificial magnesium anode and a stainless-steel cathode. Furthermore, bulk and electrode surface (both anode and cathode) precipitates are analyzed for elemental composition, crystallinity,and morphological features. The present research outcomes are expected to serve as a baseline protocol to select an optimal anode potential window in electrochemical struvite production from wastewater.
Electroforming on Additively Manufactured Mandrels
Authors: Zheng Zhaohan , Aghili Sayed MohammadAli , Wüthrich Rolf
Published: May 2020

Manufacturing industry faces recently a new challenge. Production of parts require, for various reasons, more and more low batch size production, sometimes even batch size one. Not only the batch size is reduced, but a given design has to be produced in lower on lower number too. If previously only prototyping required batch size one prodcution, the new trend of mass personalization requires it as well.

Manufacturing technologies developed over the past decades are able to produce cost effectively very complex products in high series. Low batch series production is often not possible or very costly. Additive manufacturing is a promising answer to this challenge. Additive manufacturing equipment represent however, in case of metal printing, very high investment costs and usually significant post-processing after printing is needed. An alternative way to create complex 3D printed parts in low volumes could be to use electroforming. Electroforming is commonly used to form parts on a model or, as termed in industry, a mandrel. Using additive manufacturing to create this mandrel could be a viable and cost-efficient solution. Since electroforming require less energy and less expensive equipment, it can be potentially used to create precise 3D structures. In order to create a 3D shape using electroforming.

Electroforming has its own challenges. As the thickness of the electroforming increases, voids build up and create a rough, uneven surface that has undesirable physical properties. The mass transfer at the micro-scale also changes the contribution of migration, diffusion and convection phenomena due to the scaling effect [1]. In order to produce complex and micro-scale features with acceptable quality, profile and characteristics, this paper discusses some significant factors and several methods for the improvement.

By applying appropriate potential and rotation on the mandrel during the electroforming process, deposition thickness ranging from few to several 100 microns with very low surface roughness (few microns Ra) could be achieved. The deposit thickness was very consistent too (less than 1% variation of the complete part). The homogeneity of the thickness was further investigated for various geometries to determine the limitations of the methodology.

[1] Angel, K., Tsang, H. H., Bedair, S. S., Smith, G. L., & Lazarus, N. (2018). Selective electroplating of 3D printed parts. Additive Manufacturing, 20, 164–172. doi: 10.1016/j.addma.2018.01.006
New Materials to Battle the Transistor Interconnect Bottleneck
Authors: Nies Cara-Lena , Natarajan Suresh Kondati , Nolan Michael
Published: May 2020

With ever decreasing transistor size, materials that combine both diffusion barrier and liner material properties are needed to successfully electroplate Cu and thus beat the current interconnect bottleneck. In order to facilitate coating of high aspect ratio vias, the material should be as thin as possible. One possibility to achieve this is presented in this study, where we investigate through density functional theory, the behavior Cu on Ru-doped and Ru passivated ε-TaN (1 1 0). Initially, the adsorption, diffusion and association of one and two Cu atoms on the different surfaces was studied in order to probe the early stages of film growth. This showed that, while surface diffusion of atoms was more favourable on the Ru-passivated surface, the Ru dopant acts as a nucleation site for Cu, with atoms preferentially diffusing towards it.

In order to understand the mechanism of film growth on this surface in more detail and to fine-tune the barrier and liner properties of the material, the effect of different percentages of surface doping were studied. Further, the behavior of Cu13 and Cu29 clusters on different doped surfaces and on the passivated surfaces was investigated. In particular, the study focused on the pathways toward agglomeration as well as the associated activation energies. We find that on a Ru doped surface the atoms agglomerate spontaneously to form a two-layer film, whereas they remain in a monolayer on Ru-passivated TaN (1 1 0).
(Invited) Ambipolar Quantum Dots in Planar Silicon
Authors: Sousa de Almeida Antonio , Zwanenburg Floris Arnoud
Published: May 2020

We create ambipolar quantum dots in planar silicon nanoscale transistors. We first investigate the conformity of Al, Ti and Pd nanoscale gates by means of transmission electron microscopy [1]. Next we define low-disorder electron quantum dots with Pd gates [2], and depletion-mode hole quantum dots in undoped silicon [3]. For the latter we use fixed charge in a SiO2/Al2O3 dielectric stack to induce a 2DHG at the Si/SiO2 interface. The depletion-mode design avoids complex multilayer architectures requiring precision alignment and allows directly adopting best practices already developed for depletion dots in other material systems. Finally, I will show ambipolar charge sensing: we have fabricated a single-electron transistor next to a singlehole transistor, and tuned both quantum dots to simultaneously sense charge transitions of the other quantum dot. With active charge sensing, the single-electron transistor can be tuned to detect the few-charge regime in the electron quantum dot. [4].

[1] P. C. Spruijtenburg et al., Nanotechnology, (2018).

[2] M. Brauns et al., Scientific Reports 8, 5690, (2018).

[3] S. V. Amitonov et al., Applied Physics Letters 112, 023102 (2018).

[4] A.J. Sousa de Almeida et al., https://arxiv.org/abs/2001.05045.

Figure 1
Novel HfO2-Based Multilayer Stack for Devices with Enhanced Capacitance
Authors: Moon Taehwan , Jo Sanghyun , Nam Seunggeol , Lee Yun Seong , Kim Sangwook , Lee Kwang-Hee , Heo Jinseong
Published: May 2020

Recent discovery of ferroelectricity from non-centrosymmetric orthorhombic phase (Pca21) of Hf/Zr oxides [1] has brought enormous research interests and activities because the material compatibility with CMOS process and its scalability to a few nm thickness, which have been critical issues for introducing perovskites ferroelectric (FE) materials in nanoscale devices. Physical concept of “negative capacitance” in FE materials when stacked with dielectrics (DE) has been proposed to enhance the total capacitance larger than that of DE only [2,3] and has been demonstrated in DE-FE stacks such as Al2O3/Hf0.5Zr0.5O2 or Ta2O5/Hf0.5Zr0.5O2 via transient measurement [4,5]. However, stacks with amorphous Al2O3 DE layer having relatively low dielectric constant were vulnerable to irreversible charge injection from electrodes into the DE-FE interface and thus hysteresis-free operation of the capacitor was only limited to short pulse condition below 1μs. Also Ta2O5 DE layer is often found to be defective and the film easily becomes leaky with repeated cycles.

Here we propose novel DE-FE stack based on all crystallized Hf/Zr oxides where polymorphic Hf/Zr oxides have three dominant phases, monoclinic (P21/c), orthorhombic (Pca21), and tetragonal (P42/nmc) and by varying parameters such as Zr composition and thickness in initial amorphous film, the oxides can be crystallized in phase-selective way. We employ the tetragonal phase of Hf/Zr oxide for DE layer which possesses high-k value above 30 and wide bandgap about 5.4 eV ensuring low leakage current and further enabling thickness scaling. All crystallized DE-FE stacks were fabricated on bottom electrodes via atomic layer deposition of Hf/Zr oxides with compositional variation and subsequent metal deposition and post-metallization-annealing. Electrical data from capacitance vs. voltage and polarization vs. voltage measurements manifests an intermediate characteristic between ferroelectric and anti-ferroelectric ones due to multi-phase layers. Pulsed voltage measurements and structural analyses with XRD and selective area electron diffraction will be presented to assess the proposed stack for devices with enhanced capacitance.

References

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99, 102903 (2011).

[2] S. Salahuddin, and S. Datta, Nano Letters
8, 2, 405-410 (2008).

[3] H. W. Park, J. Roh, Y. B. Lee, and C. S. Hwang, Advanced Materials
31, 32, 1805266 (2019).

[4] K. D. Kim, Y. J. Kim, M. H. Park, H. W. Park, Y. J. Kwon, Y. B. Lee, H. J. Kim, T. Moon, Y. H. Lee, S. D. Hyun, B. S. Kim, and C. S. Hwang, Advanced Functional Materials
29, 17, 1808228 (2019).

[5] M. Hoffmann, F. P. G. Fengler, M. Herzig, T. Mittmann, B. Max, U. Schroeder, R. Negrea, P. Lucian, S. Slesazeck, and T. Micholajick, Nature
565, 464-467 (2019).

Figure 1