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The barrier layer in Cu technology is essential to prevent Cu from diffusing into the dielectric layer at high temperatures; therefore, it must have a high stability and good adhesion to both Cu and the dielectric layer. In the past three decades, tantalum/tantalum nitride (Ta/TaN) has been widely used as an inter-layer to separate the dielectric layer and the Cu. However, to fulfill the demand for continuous down-scaling of the Cu technology node, traditional materials and technical processes are being challenged. Direct electrochemical deposition of Cu on top of Ta/TaN is not realistic, due to its high resistivity. Therefore, pre-deposition of a Cu seed layer by physical vapor deposition (PVD) or chemical vapor deposition (CVD) is necessary, but the non-uniformity of the Cu seed layer has a devastating effect on the defect-free fill of modern sub-20 or even sub-10 nm Cu technology nodes. New Cu diffusion barrier materials having ultra-thin size, high resistivity and stability are needed for the successful super-fill of trenches at the nanometer scale. In this review, we briefly summarize recent advances in the development of Cu diffusion-proof materials, including metals, metal alloys, self-assembled molecular layers (SAMs), two-dimensional (2D) materials and high-entropy alloys (HEAs). Also, challenges are highlighted and future research directions are suggested.

Cyanobacterial diazotrophs are considered to be the most important source of fixed N₂ in the open ocean. Biological N₂ fixation is catalyzed by the extremely O₂-sensitive nitrogenase enzyme. In cyanobacteria without specialized N₂-fixing cells (heterocysts), mechanisms such as decoupling photosynthesis from N₂ fixation in space or time are involved in protecting nitrogenase from the intracellular O₂ evolved by photosynthesis. However, it is not known how cyanobacterial cells limit O₂ diffusion across their membranes to protect nitrogenase in ambient O₂-saturated surface ocean waters. Here, we explored all known genomes of the majormarine cyanobacterial lineages for the presence of hopanoid synthesis genes, since hopanoids are a class of lipids that might act as an O₂ diffusion barrier. We found that, whereas all non−heterocyst-forming cyanobacterial diazotrophs had hopanoid synthesis genes, none of the marine Synechococcus, Prochlorococcus (non−N₂-fixing), and marine heterocyst-forming (N₂-fixing) cyanobacteria did. Finally, we conclude that hopanoid-enriched membranes are a conserved trait in non−heterocyst-forming cyanobacterial diazotrophs that might lower the permeability to extracellular O₂. This membrane property coupled with high respiration rates to decrease intracellular O₂ concentration may therefore explain how non−heterocyst-forming cyanobacterial diazotrophs can fix N₂ in the fully oxic surface ocean.

Abstract Lignin is a complex polymer deposited in the cell wall of specialised plant cells, where it provides essential cellular functions. Plants coordinate timing, location, abundance and composition of lignin deposition in response to endogenous and exogenous cues. In roots, a fine band of lignin, the Casparian strip encircles endodermal cells. This forms an extracellular barrier to solutes and water and plays a critical role in maintaining nutrient homeostasis. A signalling pathway senses the integrity of this diffusion barrier and can induce over-lignification to compensate for barrier defects. Here, we report that activation of this endodermal sensing mechanism triggers a transcriptional reprogramming strongly inducing the phenylpropanoid pathway and immune signaling. This leads to deposition of compensatory lignin that is chemically distinct from Casparian strip lignin. We also report that a complete loss of endodermal lignification drastically impacts mineral nutrients homeostasis and plant growth.

Electrode materials with appropriate mechanical, electronic and structural attributes are prerequisites for next generation renewable energy technology. An essential stage in development of batteries to achieve superior performance is selecting an appropriate anode material. In this research, application of B 3 S monolayer for anode materials has been investigated employing first-principles-based DFT. For B 3 S monolayer, as an anode material, it is anticipated to have high performance with a low sodium diffusion barrier (E a  < 0.45 eV), low open-circuit voltage (OCV∼0.12 V), and high storage capacity (1855 mA h g −1 ). In addition, metallicity of B 3 S monolayer has been maintained at the end of Na adsorption, which reveals a favorable battery operating cycle and electrical conductivity. Our findings elucidate that these outstanding attributes cause B 3 S monolayer to be an attractive option for anode materials in sodium-ion batteries (NIBs).

To solve the problem of silicide coatings on tantalum substrates failing due to elemental diffusion under high-temperature oxidation environments and to find diffusion barrier materials with excellent effects of impeding Si elemental spreading, TaB2 and TaC coatings were prepared on tantalum substrates by the encapsulation and infiltration methods, respectively. Through orthogonal experimental analysis of the raw material powder ratio and pack cementation temperature, the best experimental parameters for the preparation of TaB2 coatings were selected: powder ratio (NaF:B:Al2O3 = 2.5:1:96.5 (wt.%)) and pack cementation temperature (1050 °C). After diffusion treatment at 1200 °C for 2 h, the thickness change rate of the Si diffusion layer prepared using this process was 30.48%, which is lower than that of non-diffusion coating (36.39%). In addition, the physical and tissue morphological changes of TaC and TaB2 coatings after siliconizing treatment and thermal diffusion treatment were compared. The results prove that TaB2 is a more suitable candidate material for the diffusion barrier layer of silicide coatings on tantalum substrates.

CrN, AlN, TiN layer were prepared as diffusion barriers between the K417 substrate and Ni+CrAlYSiN nano composite coatings via vacuum arc evaporation. Oxidation kinetics and microstructure evaluation of these nano coating systems at 1000 °C after 100 h were studied. Results show that the AlN layer showed good thermodynamic stability, effectively inhibited the interdiffusion between the coating and the substrate, improved the oxidation resistance of Ni+CrAlYSiN nano composite coatings, and a single-layer Al2O3 film was formed on the coating. The CrN layer was decomposed, which did not block the diffusion of elements and had little effect on the oxidation resistance of the Ni+CrAlYSiN nano composite coating. The TiN layer effectively prevented the interdiffusion between the coating and the substrate. However, it deteriorated the oxidation resistance of the composite coating. Similar to the Ni+CrAlYSiN coating without a diffusion barrier, a double-layer oxide film structure with Al2O3 as the inner layer and Ni(Al,Cr)2O4 as the outer layer formed on the Ni+CrAlYSiN nano composite coatings with the CrN or TiN diffusion barrier.

Miniaturization in integrated circuits requires that the Cu diffusion barriers located in interconnects between the Cu metal line and the dielectric material should scale down. Replacing the conventional TaN with a 2D transition metal dichalcogenide barrier potentially offers the opportunity to scale to 1–2 nm thick barriers. In this article, it is demonstrated that MoS2 synthesized by atomic layer deposition (ALD) can be employed as a Cu diffusion barrier. ALD offers a controlled growth process at back‐end‐of‐line (BEOL) compatible temperatures. MoS2 films of different thicknesses (i.e., 2.2, 4.3, and 6.5 nm) are tested by time‐dependent dielectric breakdown (TDDB) measurements, demonstrating that ALD‐grown MoS2 can enhance dielectric lifetime by a factor up to 17 at an electric field of 7 MV cm−1. Extrapolation to lower E‐fields shows that the MoS2 barriers prepared by ALD have at least an order of magnitude higher median‐time‐to‐failure during device operation at 0.5 MV cm−1 compared with MoS2 barriers prepared by other methods. By scaling the thickness further down in future work, the ALD MoS2 films can be applied as ultrathin Cu diffusion barriers. MoS2 films prepared by atomic layer deposition (ALD) can potentially be applied as Cu diffusion barrier. Time‐dependent dielectric breakdown measurements show that MoS2 films effectively block Cu diffusion. ALD‐MoS2 films have at least an order of magnitude higher median‐time‐to‐failure at the device operation E‐field of 0.5 MV cm−1 than MoS2 prepared by other methods.

Hydrogen, while a promising sustainable energy carrier, presents challenges such as the embrittlement of materials due to its ability to penetrate and weaken their crystal structures. Here γ’‐Fe4N nitride layers, formed on iron through a cost‐effective gas nitriding, are investigated as an effective hydrogen permeation barrier. The relatively short process carried out at 570 °C consisted of pre‐nitriding in an atmosphere with higher nitriding potential, followed by treatment in a nitriding potential of 0.0016 Pa−1/2 to obtain a pure γ’ layer. A combination of screening methods, including atom probe tomography, density functional theory calculations, and hydrogen permeation analysis, revealed that the nitride layer reduces hydrogen diffusion (steady‐state hydrogen flux 3.21 x 10−8 mol/m2·s) by a factor of 20 compared to pure iron, at room temperature. This reduction is achieved by creating energetically unfavorable states due to stronger hydrogen‐binding at the surface and high energy barriers for diffusion. The findings demonstrate the potential of γ’‐Fe4N as a cost‐efficient and easy‐to‐process solution to protect metallic materials exposed to hydrogen at low temperatures, with great advantages for large‐scale applications. This study demonstrates the efficacy of γ’‐Fe4N nitride layers, formed via gas nitriding, as hydrogen permeation barriers. Advanced characterization, hydrogen permeation analysis, and DFT calculations reveal a 20 fold reduction in hydrogen diffusion at room temperature. The findings highlight γ’‐Fe4N's potential as a cost‐efficient solution for protecting metals against hydrogen embrittlement.

As the only commercialized thermoelectric for low-grade waste heat recovery applications, Bi 2 Te 3 -based devices commonly use nickel as the electrode. The long-term chemical stability of the Bi 2 Te 3 /Ni junction, particularly for the hot side, is one of the major concerns for Bi 2 Te 3 -based and other thermoelectrics because of the formation of Ni-Te intermediate compounds. The utilization of diffusion barrier layers has been proven to be an effective solution and the barriers should have both a good chemical inertness and a slow diffusion. In this work, Ti was screened out from 13 metals in total as an effective barrier material between p-type Bi 0.5 Sb 1.5 -Te 3 thermoelectric materials and Ni electrodes, because of its low diffusion coefficient and long-term interfacial stability. The fabricated p-type Bi 0.5 Sb 1.5 Te 3 /Ti/Ni single-leg devices show a conversion efficiency over 6%, at a temperature difference of 200 K, without observable degradation for 1860 cycles of measurements lasting for 10 days. This study offers a useful strategy for making efficient and durable thermoelectric devices.

Owing to the high theoretical capacity, metal sulfides have emerged as promising anode materials for potassium-ion batteries (PIBs). However, sluggish kinetics, drastic volume expansion, and polysulfide dissolution during charge/discharge result in unsatisfactory electrochemical performance. Herein, we design a core-shell structure consisting of an active bismuth sulfide core and a highly conductive sulfur-doped carbon shell (Bi 2 S 3 @SC) as a novel anode material for PIBs. Benefiting from its unique core-shell structure, this Bi 2 S 3 @SC is endowed with outstanding potassium storage performance with high specific capacity (626 mAh·g −1 under 50 mA·g −1 ) and excellent rate capability (268.9 mAh·g −1 at 1 A·g −1 ). More importantly, a Bi 2 S 3 @SC//KFe[Fe(CN) 6 ] full cell is successfully fabricated, which achieves a high reversible capacity of 257 mAh·g −1 at 50 mA·g −1 over 50 cycles, holding great potentials in practical applications. Density functional theory (DFT) calculations reveal that potassium ions have a low diffusion barrier of 0.54 eV in Bi 2 S 3 due to the weak van der Waals interactions between layers. This work heralds a promising strategy in the structural design of high-performance anode materials for PIBs.