The crevice-like nanogap stands out as one of the most potent geometries for generating intense electromagnetic field localization; however, scaling such ultrasmall nanogaps into high-density metasurfaces remains a significant challenge. We report the fabrication of dense nanocrevice metasurfaces via the directed self-assembly (DSA) of a high-χ block copolymer (BCP). Using a poly(1,1-dimethylsilacyclobutane)-block-polystyrene (PDMSB-b-PS) block copolymer with a 9 nm half-pitch, we produce periodic, anisotropic Au nanocrevice metasurfaces with sub-10 nm gap features. Comprehensive optical characterization and finite-difference time-domain (FDTD) simulations reveal a robust, tunable optical plasmonic resonance localized within the nanocrevices. Utilizing surface-enhanced Raman spectroscopy (SERS) as a sensitive probe of the near-field, we validate that these structures deliver significant field enhancement. Optimal performance is achieved at a specific Au thickness using 638 nm excitation, a condition that aligns with both the simulated resonance and experimental reflectance, thereby maximizing plasmonic enhancement. Furthermore, we demonstrate a tunable polarization response, showing that the SERS anisotropy ratio can be tuned simply by varying the deposited metal thickness. This work establishes DSA as a scalable route to designer plasmonic metasurfaces, providing a versatile platform for advanced plasmonics and polarization-resolved spectroscopy.

Herein, ZIF-derived porous carbon materials are isolated and tested for their electrochemical performances in Li-ion batteries. Whereas the stability of these materials in galvanostatic cycling is outstanding, the high irreversible capacity remains their main issue. Through an optimization work we were able to block the porosity by wet or dry impregnation of sucrose and decrease the specific surface area from 350 m 2 /g to 16.2 m 2 /g without the need of doping. This time, this change had a great impact on the irreversible capacity that dropped from 80 % to 30 %.

Solid-state batteries have attracted significant interest as promising candidates for high energy density and safe battery technology. However, they commonly experience low ionic conductivity at ambient temperature, which limits their power density. This study addresses this issue by developing a porous separator with one-dimensional (1D) nanometric channels that confine non-flammable ionic liquid-based electrolytes (IL- Li). We achieve 1D macroscopic ionic transport by confining the electrolytes within Vertically Aligned Carbon NanoTubes (VA-CNT) composite membranes. Employing quasi-elastic neutron scattering techniques, we conduct a multiscale analysis of the diffusive motion of both bulk and confined electrolytes. By extracting diffusion coefficients spanning from the molecular to macroscopic scale, we gain insights into the transport properties of IL-Li. Our results show that nanometric confinement allows to lower the operational temperature of these electrolytes by up to 20 K compared to the non-confined electrolytes. At ambient temperature, we show a tenfold increase in conductivity under 1D CNT confinement. Molecular Dynamics simulations shed light on the underlying physics, showing a unique intermolecular organization of the IL-Li under confinement. Specifically, the molecules forma core-shell structure, resulting in the creation of quasi-1D transport channels. This study presents promising avenues for exploring the use of 1D materials in energy storage applications.

The miniaturization of bending actuators is valuable for robotics, embedded systems, and medical applications, but often results in performance loss. This study presents a multilayered, screen‐printed PVDF‐TrFE (polyvinyledenedifluoride‐trifluoroethylene) actuator less than one millimeter wide, designed to achieve large bending angles. To achieve this, the various causes of performance loss are first identified through a cross‐sectional study: all influencing parameters are studied, from geometry to morphology. The geometrical profile of the layers, their design, dielectric and ferroelectric characteristics, as well as the orientation of the β ‐phase of PVDF‐TrFE responsible for the displacement are all measured. These results, coupled with the development of an analytical model, have enabled the identification of an optimized architecture as well as a new substrate capable of attaining large angles. Compared with conventional metal–insulator–metal capacitor structures, the optimized actuator features reduced margins to maximize the bending angle. Furthermore, the actuator is screen‐printed on a new type of stiff substrate (i.e., nickel, rarely used in printed electronics), which not only improves performance by 70% compared to the polyimide often used but also offers interesting features such as radio‐opacity, which is much sought‐after in the medical field.

The performances of lithium-ion batteries depend on the capability of the electrode materials to exchange lithium ions and electrons faster and reversibly. LiNiO2 is a promising electrode candidate for achieving high voltage and capacity. However, its industrialization is hindered by surface and bulk instabilities. These instabilities are due to redox processes involving charge transfer between the cations and anions. Therefore, a fundamental understanding based on further experimental evidence is required to resolve the charge transfer between the cation and anion from the surface to the bulk in LiNiO2. Herein, we resolve the roles of nickel and oxygen in the charge compensation process in LixNiO2 electrodes from the extreme surface down to 30 nm by energy dependent core-level HAXPES supported by an ab initio simulation. We emphasize the central role of oxygen in the bulk charge compensation mechanism from LiNiO2 to NiO2 due to the negative charge transfer and bond/charge disproportionation characters of LiNiO2.

The incorporation of lead-free BaTiO3 particles into P(VDF-TrFE) provides a versatile way for tuning dielectric and piezoelectric properties. Screen-printing enables the easy production of flexible capacitors. To prevent particle aggregation, the BaTiO3 particles are functionalized with a surfactant. Initially, 60 % vol. BaTiO3 particles are deposited in the second layer out of three layers. After annealing and cooling, the particle distribution is successfully homogeneous in the whole film. After poling at 80 degrees C, the relative permittivity and the piezoelectric coefficient d33 significantly increase up to 159 and 8 pC/N respectively. In situ/operando spatially-resolved X-ray techniques allow exploring the structural evolution of the composite device during annealing and during an applied electric field. The application of an electric field leads to the quasi-disappearance of the P(VDF-TrFE) ferroelectric state. As a matter of fact, the interactions between the P(VDF-TrFE) and the surfactant may limit the rotation of P(VDF-TrFE) chains near the particles. Hence, paraelectric polymers could be chosen on a mechanical or economic basis for the matrix in piezoelectric composite devices. Regarding BaTiO3, the lattice strain evolves from an extrinsic strain at RT to an intrinsic strain after annealing and cooling. At the cooled state, the tetragonality c/a is higher than 1.01, leading to improved piezoelectric properties. The increase of the average domain size leads to the increase of the composite permittivity. Finally this knowledge facilitates the development of tailored flexible piezoelectric composite devices.

The performances of lithium-ion batteries are set by the electrodes materials capacity to exchange lithium ions and electrons faster and reversibly. To this goal Ni-rich layered metal oxides, especially LiNiO2, are attractive electrode candidate to achieve both high voltage and capacities. Despite its attractiveness, several drawbacks for its industrialization are related to different form of surface and bulk instabilities. These instabilities are due to redox process involving the charge transfer between cations and anions. Therefore, a fundamental understanding based on further experimental evidence is required to resolve of charge transfer between the cation and anion from the surface to the bulk in LiNiO2. Herein, we resolve the role of nickel and oxygen in the charge compensation process in LixNiO2 electrodes from the extreme surface down to 30 nm by energy-dependent core-level HAXPES supported by ab initio simulation. We emphasize the central role of oxygen in the bulk charge compensation mechanism from LiNiO2 to NiO2 due to the negative charge transfer and bond/charge-disproportionation characters of LiNiO2. This bulk behavior is in turn responsible for surface deoxygenation and nickel reduction upon delithiation.

Sulfide-based solid electrolytes (SEs) are amongst the most promising solid electrolytes for the development of solid-state batteries (SSBs) due to their high ionic conductivity and processing advantage over oxide-based SEs. However, one of the main drawbacks of sulfide SEs is their rapid degradation in presence of humidity. In this study, we investigated the effect of exposing three different sulfide SEs (Li7P3S11, the argyrodite Li6PS5Cl and the chloride-doped argyrodite Li6-xPS5-xCl1+x) to the atmosphere of a dry room at a dew point (DP)=-40 degree celsius. For the first time to the best of our knowledge, enhanced infra-red (IR) laser technology was employed to follow and quantify online and in-situ H2S evolution by the SEs in a dry room environment over 16 h. It was found that argyrodite compounds evolved approximately 8 times less H2S compared to Li(7)P(3)S11 over 16 h of exposure with peak concentrations between 5 and 16 ppm vol. The exposed materials were studied using X-ray diffraction, Raman spectroscopy, electrochemical impedance spectroscopy, X-ray photoelectron spectrometry (XPS) and galvanostatic cycling. XPS results revealed a formation of Li2CO3 on the surface of argyrodite SEs, which served as a robust passivation layer limiting considerably reactions with the dry room atmosphere.

All-solid-state electrolytes have been extensively studied for the last years in order to achieve high conductivities and improved safety among lithium-ion technologies. Sulfide electrolytes, such as argyrodites (Li6PS5X, X = Cl, Br, and I), succeed to show high performances despite their poor chemical stability. As a matter of fact, argyrodite reactivity to water is known as a common drawback for easy implementation and requires the use of dry room for cell preparation. The understanding of argyrodite degradation under ambient air exposure is a key for the development of stable electrolytes, coatings, and processes and has been incompletely explored until now. This study brings unreported elements of comprehension around the degradation mechanisms of Li6PS5Cl solid electrolyte using transmission electron microscopy (TEM) and complementary spectroscopic techniques.

The hydrogenation step contributing to the high efficiencies (>25%) reached with poly-Si/SiOx passivated contacts solar cells is still poorly understood. In this study, Fourier transform infrared spectroscopy (FTIR) is used to follow the different bonding configurations of H during the fabrication process. The carrier lifetime degradation upon annealing is correlated to an important loss of Si–H bonds, from both the a­‑Si:H film and the SiOx interfaces. The subsequent hydrogenation step results in the formation of a small number of Si–H bonds near the crystalline silicon c-Si/SiOx interface, associated with the low stretching mode (LSM) and correlated to a significant lifetime improvement. These bonds feature a preferential orientation, as shown by polarized measurements.

Piezoelectric materials represent a great alternative to power small electronic devices with a lower environmental impact than conventional power sources. Despite significant progress on the subject, most studies focus on energy harvesting from vibrating systems. Other publications focus on the design of the piezoelectric devices, but they are hardly comparable in terms of the amount of energy collected. In this paper a new method is presented to quantitatively characterize piezoelectric energy harvesters under a single mechanical impact using a custom Charpy-like test bench. The method is illustrated by studying screen-printed piezoelectric thin films of poly(vinylidenefluoride-co-trifluoroethylene) P(VDF-TrFE), with different substrates acting as mechanical support. Devices printed on stretchable substrates allowing large deformation lead to overall better energy harvesting performance. However it is also demonstrated that the nature of the substrate influences the material properties of the piezoelectric film despite identical fabrication process.

A canonical electrolyte for lithium metal polymer batteries is PEO (Polyethylene Oxide) doped with lithium salts1. Its ionic conductivity is closely related to the local dynamics (Å, ps) of the polymer chains acting as a solid solvent. For good conductive performances, these batteries must be maintained above the melting point of the bulk PEO (TM =60°C). In order to lower this operating temperature, we propose to use one-dimensional nanoscale confinement to downshift the melting point of the confined electrolyte according to ΔTM ≈ 1/d where d is the pore diameter (Gibbs-Thomson effect)². Porous polymer composite membranes based on vertically aligned Carbon NanoTubes (VA-CNTs)3 ,4 seem to be able to meet this ambitious target. The pores are cylindrical (diameter 4nm, length 100µm) and have the particularity of being all macroscopically oriented and parallel. The effect we are seeking is driven by the curvature of the confining pore. It is then critical to ensure that only the interior of the CNTs is the permeable part of the membrane. We have followed by neutron imaging the time dependence of the penetration of the electrolyte within the membrane. We evidence a critical feature we target: only the interior of the CNTs are the permeable moieties of the membrane. As for the PEO dynamics under confinement, the electrolyte’s multiscale transport properties and ionic conductivity are characterized by PFG-NMR at the micrometer scale and Electrochemical Impedance Spectroscopy (EIS) at the macroscopic scale. We report a conductivity gain of one order of magnitude under VA-CNT confinement. Nevertheless, on a multitude of non-connected CNT pores, conductivity fluctuations are not in phase: by such classical spectroscopic techniques, only an averaged conductivity is measured. To complement the spectroscopic approach, we also probe the system by the Voltage Clamp (also called Single Pore) technique. The analysis of the conductivity noise going through a single CNT pore can indeed reveal whether the conductivity under confinement5 is due to an anomalous mobility and/or charge fluctuations. (1) Xue, Z. et al., Poly(Ethylene Oxide)-Based Electrolytes for Lithium-Ion Batteries. J. Mater. Chem. A 2015, 3 (38), 19218–19253. (2) Alba-Simionesco, C. et al., M. Effects of Confinement on Freezing and Melting. J. Phys.: Condens. Matter 2006, 18 (6), R15–R68. (3) Berrod, Q. et al., Enhanced Ionic Liquid Mobility Induced by Confinement in 1D CNT Membranes. Nanoscale 2016, 8 (15), 7845–7848. (4) Zanotti, J.-M. et al., Nanocomposite membranes for electrochemical devices. Patent WO2016151142 A1.(2016) (5) Tasserit, C. et al., Pink Noise of Ionic Conductance through Single Artificial Nanopores Revisited. Phys. Rev. Lett. 2010, 105 (26), 260602. Figure 1

A novel microporous layer structure for fuel cell application has been developed based on the direct growth of thin multiwall carbon nanotubes forests on the carbon fiber support of a commercial gas diffusion media free of hydrophobic treatment. The growth process is a hot filaments assisted chemical vapor deposition coupled with a specific catalyst dedicated to the growth of carbon nanotubes on carbon support. The so obtained carbon nanotube forests are perpendicularly aligned all along the carbon fibers and cover the surface of the gas diffusion media, providing a unique and new structure of microporous layer. The carbon nanotubes composing the forests are about 10 mu m-20 mu m long, with about 6 walls for an average diameter of 7.5-8 nm. Fuel cell testing demonstrated a performance improvement up to 30% compared to the best state of the art gas diffusion media, even in the presence of liquid water in the fuel cell, which is the main issue limiting performances. (C) 2020 Elsevier Ltd. All rights reserved.

Proton Exchange Membrane Fuel Cells (PEMFC) convert electrochemical energy into electricity. Nevertheless, the system still needs to be improved in order to be economically relevant. In that purpose, it is needed to produce more current for a reduced use of materials. Working on developing new materials for PEMFCs, managing both high gas diffusion and adequate water transport, is necessary to achieve these goals. One of the most important materials used in the fuel cell is the gas diffusion layer (GDL). A microporous layer (MPL) is generally deposited on top of the gas diffusion layer to improve gas transport and water management, and thus enhance the cell performances and stability. Carbon nanotubes interest as a MPL or as catalyst support has already been demonstrated in several works [Kannan (2009); Tang (2011); Xie (2015)]. In the literature, most of works about CNTs as microporous layers are using bulk carbon nanotubes integrated in a carbon black MPL. A few works are displacing a different microporous layer structure where carbon nanotubes are obtained by direct growth and are forming a foam around the gas diffusion layer fibers. In this work, a layer made of vertically aligned CNTs was grown in-situ on the fibers of a gas diffusion layer by a hot filaments assisted chemical vapor deposition (HFCVD). It has been possible to successfully grow aligned CNTs on different commercial supports. Functional properties of the GDL with CNTs were characterized with SEM imaging, contact angle and electrical conductivity measurements. A variety of growth time, filaments temperature, chamber temperature and gas flows have been tested. These parameters influence the carbon nanotubes length, thickness, and the CNTs forest density. At last, electrochemical characterizations were conducted in a differential single cell. This cell allows a better homogeneity of flows on the surface. Several cell configurations were studied: gas diffusion layer with carbon nanotubes on the anode, on the cathode, and on both electrodes, either in dry conditions (no condensed water) or wet conditions (with condensed water). Polarization curves have been measured to study the electrochemical phenomena leading to the variation of performances of the various cell configurations. Impedance spectroscopy has been done to measure the overall cell resistance and its intrinsic composition such as the protonic resistance or the transport resistance. SEM imaging has shown that the CNTs layers are distributed all along the carbon fibers of the GDL, also inside the GDL pores. The overall structure strictly differs from conventional microporous layers as well as other CNT-made MPLs in the literature. 10-25 µm-long multiwall carbon nanotubes with a diameter ranging between 7-10nm were obtained. CNTs as a microporous layer gives better performances (10% in dry conditions, 25% in wet conditions) than commercial MPLs. Contact angle measurements indicates that the obtained gas diffusion media (GDL+MPL) is hydrophilic, which also differs from commercial hydrophobic GDLs. Although carbon nanotubes are individually expected to be hydrophobic, the CNT forest structure and its combination with the former GDL porosity have a different property. The measurement of electrical resistance of the global fuel cell with a commercial MPL or with CNT layers shows that carbon nanotubes don’t provide a better electrical transport. Electrochemical measurements gave access to the fuel cell performance in operating conditions. The results have been compared to the reference SGL 29BC and to the Department of Energy expectations for the fuel cell performances for the next years. In dry state, GDL with CNTs work as well as the reference gas diffusion media. In wet conditions, a dramatic improvement is obtained, especially at low current density. These results are all the more interesting as the gas diffusion layer with carbon nanotubes is hydrophilic, but can compete with the hydrophobic commercial GDLs. The arrangement of carbon nanotubes might also be important as it is aligned in the direction of gas flows and water flows in the fuel cell. In closing, the results of this work show the need to develop nanostructured materials for energy applications. Carbon nanotubes proved their interest as a material for fuel cells. Even with a hydrophilic and a strictly different structure of microporous layer, the fuel cell performances with carbon nanotubes compete with the best commercial reference results. This could lead to a better understanding of the flows phenomena in fuel cells on one side, and of the predominant factors inhibiting a dramatic improvement of the PEMFCs performances. Figure 1

In this paper, we investigate, by combining electrical measurements with an atomistic-to-circuit modeling approach, the conductance of doped standalone multiwall carbon nanotubes (CNTs) as a viable candidate for the next generation of back-end-of-line interconnects. Ab initio simulations predict a doping-related shift of the Fermi level, which reduces shell chirality variability and improves electrical resistivity up to 90% by converting semiconducting shells to metallic. Electrical measurements of Pt-salt-doped CNTs provide up to 50% of resistance reduction, which is a milestone result for future CNT interconnect technology. Moreover, we find that defects and contacts introduce additional resistance, which limits the efficiency of doping, and are the primary cause for the mismatch between theoretical predictions and experimental measurements on doped CNTs.

In this paper, we report a hierarchical simulation study of the electromigration (EM) problem in Cu-carbon nanotube (CNT) composite interconnects. This paper is based on the investigation of the activation energy and self-heating temperature using a multiscale electrothermal simulation framework. We first investigate the electrical and thermal properties of Cu-CNT composites, including contact resistances, using the density functional theory and reactive force field approaches, respectively. The corresponding results are employed in macroscopic electrothermal simulations taking into account the self-heating phenomenon. Our simulations show that although Cu atoms have similar activation energies in both bulk Cu and Cu-CNT composites, Cu-CNT composite interconnects are more resistant to EM thanks to the large Lorenz number of the CNTs. Moreover, we found that a large and homogenous conductivity along the transport direction in interconnects is one of the most important design rules to minimize the EM.

In this paper, an enhanced compact model of multiwalled carbon nanotube (MWCNT) interconnects while considering defects and contact resistance is proposed. Based on the atomistic-level simulations, we have found that defect densities impact MWCNT resistance and ultimately their electrical performance. Furthermore, we have computed by atomistic-level simulations, the end-contact resistance between single-wall carbon nanotube and palladium (Pd) electrode to mimic the Pd–CNT end-contact resistance of each CNT shell in MWCNT. We have developed an advanced shell-by-shell model to include various parameters, such as shell diameter, shell chirality, defects on each shell, and connectivity of each shell to end contacts. We run Monte Carlo simulations to perform variability studies on each of these parameters to understand the electrical performance variation on MWCNT interconnects. We present the simulation results to convey the critical impact of variations. The impact of doping on MWCNT variability in the form of Fermi level shift will be addressed in Part II of this paper.

This article is a review of the current progress and results obtained in the European H2020 CONNECT project. Amongst all the research on carbon nanotube interconnects, those discussed here cover 1) process & growth of carbon nanotube interconnects compatible with back-end-of-line integration, 2) modeling and simulation from atomistic to circuit-level bench-marking and performance prediction, and 3) characterization and electrical measurements. We provide an overview of the current advancements on carbon nanotube interconnects and also regarding the prospects for designing energy efficient integrated circuits. Each selected category is presented in an accessible manner aiming to serve as a review and informative cornerstone on carbon nanotube interconnects.

We have performed statistical atomistic simulations with tight-binding approach to investigate the effects of randomly distributed mono-vacancy defects in metallic single-walled carbon nanotube (SWCNT) interconnects. We also extracted defective resistances from the atomistic simulations and performed circuit-level simulations to compare the performance of interconnects with and without defects. We have found that the defects induce significant fluctuations of SWCNT resistance with a median value showing an Ohmic-like behaviour. Fortunately, the resistance depends only on the diameter of SWCNTs and not on their chirality. Moreover, our circuit simulations show that the defective resistance induces important propagation time delay ratio that should be accounted for when designing CNT interconnects.