bluuebunny/crossref_metadata_2025_split huggingface dataset:
Influence of Pre-Oxidation on Dual Atmosphere Effect on AISI 441 Interconnects for Solid Oxide Fuel Cell Applications
Authors: Goebel Claudia , Alnegren Patrik , Faust Robin Leonard , Svensson Jan-Erik , Froitzheim Jan 
Published: February 2020

Interconnects are an integral part of solid oxide fuels cells (SOFC) and, even when ferritic stainless steel is used, their contribution to the overall stack cost is still substantial. Stainless steels that are produced in large volumes such as AISI 441 are particularly attractive from a cost perspective. However, in our previous work, we have shown that this material suffers from severe corrosion in dual atmosphere exposure at 600 °C typical for Intermediate Temperature-SOFC (IT-SOFC) applications. We have seen a beneficiary effect of pre-oxidation and will, in the present work, closely examine this effect. By varying pre-oxidation parameters such as length and location (anode vs. cathode side) of the oxide layer, we were able to clarify the importance of pre-oxidation. Furthermore, we see a correlation between the length of pre-oxidation, and therefore the thickness of the oxide layer, and the onset of breakaway oxidation. This correlation is expected to allow for accelerated life time testing with respect to dual atmosphere corrosion.
For our studies we chose five different pre-oxidation times: 0 min, 11 min, 45 min, 180 min and 280 min. The dual atmosphere exposure was conducted at 600 °C and the exposure was interrupted after 24 h, 168 h and 500 h and photographs were taken of the air facing side of each steel sample. By means of the photographs, we can clearly correlate length of pre-oxidation with onset of breakaway. Our findings are further supported by Scanning Electron Microscopy/Energy Dispersive X-Ray (SEM/EDX) analysis.
An additional study was performed to get a clear picture of the beneficial effects of the pre-oxidation layer in relation to its location. To examine this question the samples were pre-oxidized and subsequently the resulting oxide layer was removed from one side of the sample via mechanical polishing. The samples were then exposed with the pre-oxidized surface either facing the fuel side or facing the air side. The exposure was interrupted after the same intervals as in the aforementioned experiment to visualize the progress of breakaway oxidation. Also these samples were analyzed using photographs and SEM/EDX analysis.
Analysis of Temperature Gradients in Lithium-Ion Batteries By Electrothermal Impedance Spectroscopy (ETIS)
Authors: Dippon Michael , Weber André , Ivers-Tiffée Ellen 
Published: February 2020

While the surface temperature (Tsurf) of a lithium-ion cell is measurable by an external temperature sensor, the internal temperature (Tint) remains unknown. The difference between the surface temperature and the internal temperature increases with charging/discharging rate and with cell volume. A thermal model describing the correlation between load and cell temperature is necessitated, and requires reliable parameter settings.
The electrothermal impedance spectroscopy (ETIS) is an in-situ method, which determines the thermal impedance and parameterizes a thermal model. ETIS is comparable with electrochemical impedance spectroscopy (EIS), but in ETIS the excitation signal is a sinusoidal heat flow q(t), which leads to a sinusoidal temperature response (Tint(t) and Tsurf(t)). From the input signal q(t) and output signal T(t) the thermal impedance can be calculated. Using a simple thermal model (Figure 1 b)) and the measured thermal impedance (Figure 1 a)), the temperature change and the difference between the internal temperature and the surface temperature can be calculated as a function of the load current.
Consequently, the ETIS-Method was applied to a high energy (KOKAM 560 mAh) and to a high power (KOKAM 350 mAh) lithium-ion pouch cell. Both are made of a NCA-LCO blend cathode and a graphite anode, but differ in electrode thickness.
The study shows that the simple model from Figure 1 b) sufficiently describes the thermal behavior of both commercial cell types. The parametrized model describes fairly well the thermal gradient from Tsurf to Tint and is capable to quantify the thermal gradients in lithium-ion cells. The thermal resistance Rth of the high energy pouch cell is more than doubled (2.5 K/W) comparing to the high power cell (1 K/W), thus reflecting the influence of electrode thickness to the thermal behavior of a lithium-ion cell.

Figure 1
Physical Interpretations of Impedance Spectra for Pseudocapacitive Electrodes
Authors: Mei Bing-Ang , Pilon Laurent 
Published: February 2020

Electrochemical impedance spectroscopy (EIS) has been used widely to determine the properties of pseudocapacitive electrodes. It consists of applying a low-amplitude sinusoidal voltage to a steady-state potential and measuring the output sinusoidal current. Using complex notations, the impedance of the electrodes can be determined by dividing the oscillating potential by the oscillating current. The impedance spectra, including the Nyquist plots and Bode plots, are informative to determine the properties of the electrodes. However, the interpretation of impedance spectra has been a “subject of controversy”.
This study aims to provide physical insights in interpreting the impedance spectra of pseudocapacitive electrodes by numerically reproducing EIS measurements in a three-electrode setup. The continuum model used was based on the modified Poisson-Nernst-Planck model combined with the Butler-Volmer equation and accounted for (i) charge transport in both electrodes and electrolyte, (ii) the dynamics of the electric double layer, (iii) steric repulsion due to finite ion sizes, (iv) reversible redox reactions, and (v) intercalation. The effect of the electrode and electrolyte resistance, charge transfer resistance at the electrode/electrolyte interface were separated numerically by varying the bulk ion concentration, electrolyte length, redox reaction rate constant, and the steady-state potential, i.e., the biased potential. Moreover, the faradaic and capacitive contributions of the impedance can be interpreted separately. Therefore, the behaviour in each frequency regime in the impedance spectra can be related to specific physical processes.
Single-Step Deposition of Nanostructured Fe2O3 as Anode for Li-Ion Batteries
Authors: Wang Yang , Roller Justin , Maric Radenka 
Published: February 2020

Alpha phase iron oxide has been investigated as active anode material for lithium ion batteries because of high theoretical specific capacity, low cost and eco-friendly nature. Porous nanostructured electrode materials directly deposited on current collectors effectively enhance the rate performance of Li-ion batteries. The unique structure provides open channels for electrolyte penetration and short diffusion pathways for Li ions and electrons. In addition, the open spaces can accommodate the large volume change from the repeated conversion reaction of α-Fe2O3 during cycling.
A simple and economical manufacturing approach of the nanostructured electrodes is essential to the development and application of the next generation Li-ion batteries. In this study, nanostructured α-Fe2O3 electrodes are fabricated by reactive spray deposition technology (RSDT) which is a single-step flame combustion synthesis method. This process is continuous and scalable. The structure and morphology of as-prepared electrode are investigated by X-ray diffraction, scanning electron microscopy and transmission electron microscopy. Electrochemical properties of the nanostructured α-Fe2O3 electrodes are studied using cyclic voltammetry, galvanostatic charge/discharge cycling and electrochemical impedance spectroscopy in half-cell configuration.
Understanding the Dynamics of Primary Zn-MnO2 Alkaline Battery Gassing with Operando Visualization and Pressure Cells
Authors: Faegh Ehsan , Omasta Travis J , Hull Matt , Zuraw Michael , Mustain William E 
Published: February 2020

The leading cause for safety vent rupture in alkaline cells is the intrinsic instability of zinc in the highly alkaline reacting environment. Zinc and aqueous KOH react in a parasitic process to generate hydrogen gas, which can rupture the seal and vent the hydrogen along with small amounts of electrolyte. The expelled electrolyte is known to cause damage to consumer electronics equipment, and also leads to brand damage. Under most circumstances, cells are engineered to slow the hydrogen evolution process, and its effects are never apparent to the end user. However, abusive conditions (i.e. over discharge) can accelerate the rate of gassing. Industry leaders have been cognizant of this for years, and improved techniques to understand and mitigate zinc corrosion have long been desired.
In order to understand the fundamental drivers and mechanisms for such gassing behavior, our team has developed a new research platform that enables a cross-sectional view of the cell during charge and discharge (Figure 1). There also exists version of the cell that can actively measure pressure as well as the potential distribution across the cell. In this study, several parameters were investigated and it was confirmed that the formation of high surface area (or so-called “black”) zinc during cell discharge was the root cause for accelerated gassing. Steep concentration gradients caused by the cell balance and chemistry are responsible for black zinc formation and subsequent hydrogen evolution. Also, it was confirmed that in deeply discharged cells, significant hydrogen evolution does not occur during discharge because of unfavorable electrochemical conditions; gassing occurs when the cell is off load. In this talk, the fundamental mechanisms and operational parameters controlling black zinc formation will be discussed. Also, possible pathways forward for action and further research will be proposed.

Figure 1
(Nanocarbons Division SES Young Investigator Award Address) Bottom-up Synthesis of Semiconducting Graphene Nanoribbons via CVD
Authors: Arnold Michael S 
Published: February 2020

We have discovered how to drive graphene crystal growth with a large shape anisotropy through control of kinetics on the surface of Ge(001) single crystal wafers via CH4 chemical vapor deposition. This discovery enables the direct synthesis of narrow, armchair, semiconducting nanoribbons. The ribbons are self-orienting, self-defining, and have smooth edges. The ribbons exhibit exceptional transport properties (e.g., high on-state conductance and on/off ratio at room temperature) and provide a promising pathway towards the direct integration of high-performance nanocarbon electronics onto conventional semiconductor wafer platforms.
This talk will detail the synthesis of these ribbons (including seeded arrays of ribbons), the elucidation of their structure, and the characterization of their promising charge transport properties.

M. Jacobberger, B. Kiraly, M. Fortin-Deschenes, P. L. Levesque, K. M. McElhinny, G. J. Brady, Richard Rojas Delgado, S. Singha Roy, A. Mannix, M. G. Lagally, P. G. Evans, P. Desjardins, R. Martel, M. C. Hersam, N. P. Guisinger, M. S. Arnold, Direct Oriented Growth of Armchair Graphene Nanoribbons on Germanium, NATURE COMMUNICATIONS, 6, 8006 (2015).

Kiraly, A. J. Mannix, R. M. Jacobberger, B. L. Fisher, M. S. Arnold, M. C. Hersam, N. P. Guisinger, Sub-5 nm, Globally Aligned Graphene Nanoribbons on Ge (001), APPLIED PHYSICS LETTERS, 108, 213101 (2016).

M. Jacobberger, M. S. Arnold, High Performance Charge Transport in Semiconducting Armchair Graphene Nanoribbons Grown Directly on Germanium. ACS NANO, 11, 8924 (2017).

J. Way, R. M. Jacobberger, M. S. Arnold, Seed-Initiated Anisotropic Growth of Unidirectional Armchair Graphene Nanoribbon Arrays on Germanium, SUBMITTED (2017).

S. Arnold, R. M. Jacobberger, Oriented Bottom-Up Growth of Armchair Graphene Nanoribbons on Germanium, U.S. PATENT 9,287,359 (2016).

S. Arnold, A. J. Way, R. M. Jacobberger, Seed-Mediated Growth of Patterned Graphene Nanoribbon Arrays, U.S. PATENT 9,761,669 (2017).
(Invited) In Situ scanning Tunneling Microscopy Studies of hBN Layer Growth Kinetics and the Influence of Substrate on Electronic Structure of the Layers
Authors: Arias Pedro , Abdulslam Abdulfattah , Ebnonnasir Abbas , Ciobanu Cristian V , Kodambaka Suneel 
Published: February 2020

Two-dimensional (2D) layered materials, owing to a wide range of properties (e.g., graphene is metallic, hBN is insulating, and MoS2 is semiconducting), have attracted considerable attention over the past decade. hBN is isostructural to graphene and is considered an ideal dielectric for the fabrication of vertical 2D layered heterostructures with potential applications in optoelectronics and nanoelectronics. hBN layers are commonly grown on metal substrates. In contrast to free-standing hBN layers, substrate-supported hBN can be metallic, semiconducting, or insulating, depending on the chemistry and electronic structure of the hBN/substrate interface. Moreover, due to relatively weak van der Waals interactions between the 2D layer and the substrate, orientational registry of the layers with the substrate is not expected and is often difficult to control. While the growth and electronic structure of graphene layers have been fairly well studied, relatively little is known concerning the mechanisms underlying the growth of the hBN layers and the influence of hBN domain orientation (with respect to the substrate) on its electronic properties.
Using in situ ultra-high vacuum scanning tunneling microscopy (UHV STM), we investigated the chemical vapor deposition (CVD) kinetics of hBN on Pd(111). STM images are acquired during CVD of borazine as a function of substrate temperature, borazine flux, and deposition time. We observe the nucleation and growth of chemisorbed borazine islands on the Pd surfaces. Furthermore, we investigated the surface structure of hBN domains on Pd(111) using STM, scanning tunneling spectroscopy (STS), and density functional theory (DFT) calculations. STM images acquired from the hBN/Pd(111) sample reveal moiré patterns with at least four different periodicities λ corresponding to four rotational domains of hBN. From the STM images, we measured the surface corrugations in each of the moiré patterns and found that the corrugation amplitude Δz depends on the tunneling bias and increases with increasing λ. We suggest that Δz is a measure of hBN-Pd(111) interaction strength and attribute the higher corrugation amplitudes to stronger interactions between the hBN domains and the Pd(111). We expect that similar approach could be used to investigate growth kinetics and orientation-dependent interactions in other substrate-supported 2D layers with large lattice mismatch with respect to the substrate.
(Invited) Epitaxy of 2D Transition Metal Dichalcogenide Monolayers and Heterostructures
Authors: Zhang Xiaotian , Choudhury Tanushree , Chubarov Mikhail , Redwing Joan M. 
Published: February 2020

There is growing interest in monolayer transition metal dichalcogenides (TMDs) such as MoS2 and WSe2 and related 2D heterostructures due to their compelling electronic and photonic properties. The majority of this work has been carried out using ultra-thin flakes exfoliated from bulk chalcogenide crystals but future device development requires the ability to synthesize large area single crystal films and heterostructures. Our research is aimed at the development of an epitaxial growth technology for layered dichalcogenides, similar to that which exists for III-V and other compound semiconductors, based on gas source chemical vapor deposition (CVD). This approach provides a high overpressure of chalcogen species needed to maintain stable growth at elevated temperature and excellent control of the precursor partial pressures to achieve layer-by-layer and heterostructure growth.
Our recent studies have focused on the epitaxial growth of WSe2 and WS2 monolayer films and heterostructures using metal hexacarbonyl and hydride chalcogen precursors on substrates including sapphire and hexagonal boron nitride (hBN). A multi-step precursor modulation growth method was developed to independently control nucleation density and the lateral growth rate of WSe2 and WS2 monolayer domains on the substrate. This approach also enables measurement of W-species surface diffusivity and domain growth rate as a function of growth conditions providing insight into the fundamental mechanisms of monolayer growth. Using this approach, coalesced monolayer and few-layer TMD films were obtained on sapphire substrates up to 2” in diameter at growth rates on the order of ~ 1 monolayer/hour. In-plane X-ray diffraction demonstrates that the films are epitaxially oriented with respect to the sapphire resulting from a merging of an equal mixture of 0o and 60o oriented domains. WSe2 also grows epitaxially on hBN single crystal flakes but in this case the domains exhibit a predominant direction resulting in a reduced density of anti-phase boundaries. Applications and challenges of this approach in the growth of 2D heterostructures will also be discussed.
(Invited) Resonance Raman Spectroscopy in New 2D Materials
Authors: Pimenta Marcos A 
Published: February 2020

The pioneering experiments with graphene in 2004 opened the new area of two-dimensional (2D) systems in science. Several new 2D systems have been studied, such as the semiconducting transition metal dichalcogenides MX2 (M = Mo, W and X = S, Se, Te), and a phosphorus crystalline halotropic called black phosphorus. The behavior of the electrons in these materials depends not only on the atoms in the crystalline structure but also on the number of layers and the form of stacking. We have in recent years studied some of these 2D materials by Raman spectroscopy, which provides us with information about phonons and their interactions with electrons and excitons. In this work, I will initially present Raman spectroscopy results in MoS2, [1,2], WS2 and WSe2 [3] compounds, which show that Raman modes are intensified by resonances with excitons, allowing us to obtain dependence of their energies with the number of atomic layers. We observed that the electron-phonon coupling is dependent on the symmetry of the excitons and phonons [1] and we could evidence electron scattering processes between different valleys by acoustic phonons [2]. Finally, I will present results on black phosphorus, which has peculiar anisotropic electronic bands. Different edges of black phosphorus were studied using Raman spectroscopy and the results show the appearance of new modes at the edges of the sample, which depend on the atomic structure of the edges (zig-zag or armchair). Theoretical simulations confirm that the existence of new modes is due to edge phonons, which are originated by the atomic rearrangements at the crystalline terminations [4]..
[1] B. R. Carvalho, Phys. Rev. Letters 114, 136403 (2015)
[2] B. R. Carvalho et al. Nature Comm. (2017)
[3] E. del Corro et al, Nano Letters 16 (4), pp 2363–2368 (2016)
[4] H. B. Ribeiro et al, Nature Comm. vol 7, 12191 (2016)
Colloidal, Nanoelectronic State Machines Based on 2D Materials for Aerosolizable Electronics
Authors: Koman Volodymyr , Liu Pingwei , Kozawa Daichi , Liu Albert Tianxiang , Cottrill Anton , Strano Michael S 
Published: February 2020

A here-to- fore unexplored property of 2D electronic materials such as graphene, hexagonal boron
nitride, and MoS2 is the ability to graft electronic circuits, transistors, memory, and sensors onto
colloidal particles. Such particles can access local hydrodynamics in fluids to impart mobility and can
otherwise access spaces inaccessible to conventional electronics. Herein, we develop a 2D material
transfer approach combined with conventional lithography to pattern completed, functional circuits on
SU-8 particles (100x100x1 µm3 ) that function as fully autonomous state machines. The circuits are
powered by a p-n heterojunction of MoS2 and WSe2 operating as a photodiode, which powers, as a
chemiresistor circuit element, a distinct MoS2 monolayer for the detection of VOCs or carbon
particulates. Finally, the electrical output is irreversibly stored in a memristor device placed in series
consisting as a distinct MoS2 flake sandwiched between Au and Ag electrodes and protected from the
environment by hBN monolayer. These colloidal state machines are capable of operation after
aerosolization and hydrodynamic propulsion to a target over 0.6 m away. The devices can successfully
detect the presence of select analytes while aerosolized, storing this information in memory on the
particle for retrieval upon capture. An incorporated retroreflector design of the system allows for facile
position location using optical detection. Such state machines, enabled by 2D nanoelectronics, may find
widespread application as probes in the human digestive tract, oil and gas conduits, chemical and
biosynthetic reactors, and as autonomous environmental sensors.
(Invited) 2D Materials Heterostructures for Electronic Applications
Authors: Fiori Gianluca 
Published: February 2020

In this talk, I will present the perspectives of two-dimensional material heterostructures devices for electronic applications. To this purpose, we will exploit really accurate multi-scale, multi-physics numerical simulations able to predict device performance under different working conditions.
This is indeed a powerful approach, in order to assess which solutions are the most promising, and those that will never meet industry requirements.
I will also provide some perspectives regarding 2DMs inkjet printed devices, as an interesting solution to print on-demand and on flexible substrates electronic systems.
(Invited) All-Carbon Interconnects - from 1D to 3D
Authors: Yang Cary Y 
Published: February 2020

Continuous downward scaling in silicon integrated circuit technology into the sub-20 nm regime has created critical challenges in chip manufacturing, among them, reliability and performance of on-chip interconnects. Current interconnect materials, Cu and W, face increased reliability challenges in the nanoscale as a result of electromigration failures at high current densities. Materials such as nanocarbons, metal silicides, and metallic nanowires are being considered as potential replacements for Cu and W. In particular, due to its superior electrical and mechanical properties as well as much higher current-carrying capacities, carbon nanotube (CNT) is a serious contender to replace Cu and W in on-chip interconnect via. However, the main challenge to functionalizing CNT vias is the metal-CNT contact resistance. To mitigate such challenge, a seamless three-dimensional all-carbon interconnect structure has been fabricated by growing CNTs directly on one or few layers of graphene (MLG). This 3D structure can potentially yield low resistance due to the strong C-C sp2 bonding in CNT and graphene and across the CNT-graphene interface. While such growth has been demonstrated, the CNT/graphene interfacial nanostructure and how it impacts the electrical properties of the 3D structure are far from being understood.
Our test structure consists of MLG grown by annealing a Ni thin film in H2/CH4 ambient inside a low-pressure PECVD chamber, before being transferred onto an oxide-covered silicon substrate. Vertically aligned CNTs are then grown on the transferred MLG in a PECVD system using a similar recipe as in our previous work on CNT vias, resulting in a 3D all-carbon interconnect structure. Scanning and transmission electron microscopy images reveal CNT alignment and interfacial nanostructure comparable to the CNT-Cr interface in CNT via. The measured resistance of the 3D structure is compared with those of sub-100 nm linewidth CNT vias. Our results demonstrate the feasibility of fabricating a 3D CNT/graphene device, which can serve as the building block for all-carbon interconnects. Enhanced understanding of the relationship between interfacial nanostructure and device resistance can lead to eventual functionalization of contacts between CNT vias and a graphene-based planar interconnect network in the most advanced technology nodes.