Abstract: Garnet-type solid electrolytes are suitable for solid-state batteries with a lithium metal anode, but it is challenging to fabricate garnet-based lithium metal batteries with a long cycle life at high rates. This study demonstrates that a mosaic Li7Sn3/LiF interface layer formed in situ on the surface of garnet-type Li6.75La3Zr1.75Ta0.25O12 (LLZT) through the reaction between a SnF2 coating layer and a lithium metal enables stable, high-rate cycling for LLZT-based batteries. The interface layer possesses a nanomosaic structure of Li7Sn3 nanoparticles and surrounding LiF, enabling fast lithium-ion conduction. Meanwhile, ion insulating Li2CO3 on the surface of LLZT pellets is completely removed by SnF2 during the formation of the interface layer, which reduces the ion diffusion barrier from LLZT to the lithium anode. Benefiting from the advantageous interface layer, LiFePO4∥SnF2-LLZT∥Li cells show superior cycle performance over 200 cycles at 1 C (272 μA cm-2) with a capacity of 140.6 mAh g-1 (94.6% retention) at 30 °C. Even at 2 C, a capacity of 102.9 mAh g-1 remains after 200 cycles. This work provides an optimal interfacial structure to enhance lithium-ion migration between garnet electrolytes and a lithium metal and paves the way for developing high-performance solid-state batteries.

Abstract: The focus of this paper is how to efficiently enhance the thermal conductance of gallium-based thermal interface materials (TIMs) and greatly avoid the excessive consumption of liquid metal during its application. Highly heat-conducting diamond particles are selected as the reinforced additives for pure gallium on account of their mature technology of surface metallization. To improve the interface combination status between those inorganic fillers and liquid metal matrix, chromium transition layer is deposited on the surfaces of diamond particles by magnetron sputtering method. The phase composition of cladding layer on diamond particles is analyzed by transmission electron microscopy combined with focused ion beam technology. To measure the thermal conductivity of gallium-based TIM filled with chromium-coated diamond particles, a specific three-layer structure sample is made for laser flash analysis and the corresponding theoretical fitting model is deduced subsequently. After performing iterative solution through programming, our results present that 47 wt% addition of chromium-coated diamond particles can dramatically increase the thermal conductivity of pure gallium from 29.3 to 112.5 W/(m·K) at room temperature. And fortunately, it has not yet been observed that the chromium coating is over consumed by liquid metal or the thermal conductivity of composite seriously degrades after thermal aging treatment at 80 °C for 192 h, strongly indicating that chromium could be used as the diffusion barrier layer for heat-conducting particles and the metal substrates to maintain long-term reliable service of gallium-based TIMs.

Abstract: The interconnect half-pitch size will reach ≈20 nm in the coming sub-5 nm technology node. Meanwhile, the TaN/Ta (barrier/liner) bilayer stack has to be >4 nm to ensure acceptable liner and diffusion barrier properties. Since TaN/Ta occupy a significant portion of the interconnect cross-section and they are much more resistive than Cu, the effective conductance of an ultrascaled interconnect will be compromised by the thick bilayer. Therefore, 2D layered materials have been explored as diffusion barrier alternatives. However, many of the proposed 2D barriers are prepared at too high temperatures to be compatible with the back-end-of-line (BEOL) technology. In addition, as important as the diffusion barrier properties, the liner properties of 2D materials must be evaluated, which has not yet been pursued. Here, a 2D layered tantalum sulfide (TaSx ) with ≈1.5 nm thickness is developed to replace the conventional TaN/Ta bilayer. The TaSx ultrathin film is industry-friendly, BEOL-compatible, and can be directly prepared on dielectrics. The results show superior barrier/liner properties of TaSx compared to the TaN/Ta bilayer. This single-stack material, serving as both a liner and a barrier, will enable continued scaling of interconnects beyond 5 nm node.

Abstract: The influence of Na diffusion from various glass substrates during a high-temperature slenization process on the microstructure and morphology of two-step formed CIGS absorber layers is investigated. In order to minimise the CIGS absorber formation time, elemental Se vapour is used to prepare the CIGS absorber. The grain sizes of the CIGS films are found to increase with increasing sodium in the glass substrates (extra clear glass, soda-lime glass, borosilicate glass). TiN and SiN thin films are used as diffusion barrier layers inserted between the glass substrate and the Mo rear conatct to tune the Na diffusion from the soda-lime glass. The interdiffusion between the In-rich CuInSe2 surface layer and the Ga-rich CuGaSe2 layer is promoted by the barrier layer, leading to larger CIGS grains. Efforts are also taken to understand the differences in Na diffusion (from the glass substrates) and their effects on the MoSe2 intermediate layer formation during the high-temperature CIGS absorber formation processes. We find that excess amounts of Na and Se are essential for the MoSe2 growth. The excessive Na in the form of Na2Sex at the CIGS/Mo interface works as a Se source and catalyses the MoSe2 formation. The Se flow in the two-step CIGS formation process must be sufficiently high to obtain high-efficiency CIGS solar cells.

Abstract: Graphene/metal oxides (G/MO) composite materials have attracted much attention as the anode of sodium ion batteries (SIBs), because of the high theoretical capacity. However, most metal oxides operate based on the conversion mechanism and the alloying mechanism has changed to Na2O after the first cycle. The influence of G/Na2O (G/N) on the subsequent sodiation process has never been clearly elucidated. In this work, we report a systematic investigation on the G/N interface from both aspects of theoretical simulation and experiment characterization. By applied first-principles simulations, we find that the sluggish kinetics in the G/MO materials is mainly caused by the high diffusion barrier (0.51 eV) inside the Na2O bulk, while the G/N interface shows a much faster transport kinetics (0.25 eV) via unique double-interstitialcy mechanism. G/N interface possesses an interfacial storage of Na atom through the charge separation mechanism. The experimental evidence confirms that high interfacial ratio structure of G/N greatly improves the rate performance and endows G/MO materials the interfacial storage. Furthermore, the experimental investigation finds that the high interfacial ratio structure of G/N also benefits from the reversible reaction between SnO2 and Sn during cycling. Lastly, the effects of (N, O, S) doping in graphene systems at the G/N interface were also explored. This work provides a fundamental comprehension on the G/MO interface structure during the sodiation process, which is helpful to design energy storage materials with high rate performance and large capacity.

Abstract: Stainless steel (SS) foil is made of abundant materials and is a durable and flexible substrate, but the efficiency of a solar cell on SS foil deteriorates via the diffusion of impurities from the SS substrate into a Cu2ZnSn(S,Se)4 (CZTSSe) absorber layer. In this work, the properties of the diffusion barrier for CZTSSe solar cells is investigated by X-ray diffraction (XRD), secondary ion mass spectrometry (SIMS), and scanning electron microscopy (SEM). The industrially relevant oxide materials ZnO and SiO2 are used as diffusion barriers against impurities. The formation of a ZnSe reaction with Se degrades the barrier properties of the ZnO barrier layer. As a result, ZnO fails to act as a diffusion barrier, and Fe is observed in the absorber layer. On the other hand, the intrinsic diffusion barrier properties of SiO2 are superior to those of ZnO, and SiO2 is a stable diffusion barrier even after selenization. Therefore, SiO2 was applied to flexible solar cells, and a power conversion efficiency of 10.30%, the highest efficiency for CZTSSe on SS foil, was obtained.

Abstract: Delamination and high series resistance due to excessively thick MoSe2 are commonly found in solution-processed CIGS solar cells. This work shows the effective functionality of Mo–N as a back contact barrier against selenium diffusion during high temperature selenization. Mo–N barrier layers are deposited by reactive D.C. magnetron sputtering. The Mo–N barrier layer significantly reduces MoSe2 formation at the Mo/CIGS interface and consequently improves adhesion properties and enhances crystallinity of the CIGS absorber. The power conversion efficiency (PCE) of a spray-coated diamine–dithiol based CIGS solar cell improved from our previously published 9.8% to 12.0% after application of the Mo–N back contact barrier layer.

Abstract: Intermetallics form a versatile group of materials that possess unique properties ranging from superconductivity to giant magnetoresistance. The intermetallic Co–Sn and Ni–Sn compounds are promising materials for magnetic applications as well as for anodes in lithium‐ and sodium‐ion batteries. Herein, a method is presented for the preparation of Co3Sn2 and Ni3Sn2 thin films using diamine adducts of cobalt(II) and nickel(II) chlorides, CoCl2(TMEDA) and NiCl2(TMPDA) (TMEDA = N,N,N′,N′‐tetramethylethylenediamine, TMPDA = N,N,N′,N′‐tetramethyl‐1,3‐propanediamine) combined with tributyltin hydride. The films are grown by atomic layer deposition (ALD), a technique that enables conformal film deposition with sub‐nanometer thickness control. The Co3Sn2 process fulfills the typical ALD qualifications, such as self‐limiting growth, excellent film uniformity, and conformal coverage of a trench structure. X‐ray diffraction (XRD) shows reflections characteristic to the hexagonal Co3Sn2 phase, which confirms that the films are, indeed, intermetallic instead of being mere alloys of Co and Sn. The films are extremely pure with impurity levels each below 1.0 at.%. Ni3Sn2 films similarly exhibit the expected XRD reflections for the intermetallic phase and are of high purity. The Co3Sn2 film show magnetic hysteresis with high coercivity values exceeding 500 Oe, indicating great potential in terms of applicability of the films.

Abstract: CexZr1-xO2 (x = 0.25, 0.5 and 0.75) was synthesized by solid phase chemical reaction synthesis and characterized by X-ray diffraction (XRD), thermal expansion, Hebb-Wagner method and DC van der Pauw method. ZrO2 has a high melting point and CeO2 has a variable valence state, which can make the CexZr1-xO2 material have mixed ionic-electronic conductivity and stability. The synthesis method has the advantages of having a lower synthesis temperature and no waste liquid discharge, which is beneficial to energy conservation and environmental protection. A limiting current oxygen sensor was prepared with Ce0.75Zr0.25O2 dense diffusion barrier and ZrO2 stabilized by 9 mol% Y2O3 (9YSZ) solid electrolyte by Pt sintered-paste method. Limiting current plateau of the oxygen sensor was obtained and the effects of operate temperature (T), oxygen concentration (x(O2)) and water vapor pressure (p(H2O)) on the limiting current was studied, respectively. The results show that the Ce0.75Zr0.25O2 material has maximum electronic and total conductivity at 800 oC and is the most suitable ceramic material to be a dense diffusion barrier of limiting current oxygen sensor. The oxygen sensor exhibits good sensing characteristics under different research conditions, including different T, x(O2) and p(H2O). The limiting current is related to various research factors, for example, log(IL·T) depends linearly on 1000/T, IL depends linearly on x(O2) and IL is not influenced obviously by p(H2O). The experiment supplements the application of mixed conductor material CexZr1-xO2 (x = 0.25, 0.5 and 0.75) as a dense diffusion barrier in limiting current oxygen sensor.

Abstract: We investigated the diffusion properties of metal atoms in van der Waals layered materials using first-principles calculations combined with group theory analysis. We found that there is an abnormal diffusion behavior of Cu in MoS2, which originated from the competition of the electronic and strain energies. Although the atom diffusing in bulk MoS2 constantly changes the symmetry of the system with reduced electronic energy due to p–d coupling between occupied Cu d and unoccupied anion p states, the strain energy is dominant. As a result, the energy barrier of metal atoms is mainly determined by their size, making the diffusion rate of Cu faster than those of other metal atoms. Nevertheless, in the monolayer MoS2, the strain energy is negligible and the electronic coupling is significant, so that the strong d–d coupling between occupied Cu d and unoccupied cation d states leads to the highest diffusion barrier of Cu atoms.

Abstract: The stability and control of copper (Cu) electrode application in oxide semiconductor indium gallium zinc oxide (IGZO) can improve the resistance–capacitance (RC) delay, which is greatly critical f...

Abstract: Compared with nanosized materials, the long-pathway isolation of the interior part from the electrolyte for bulk electrode materials may result in high ionic diffusion barrier, leading to the poor

Abstract: The concept of a core–shell metallic structures, with a few atomic layers of the “shell” metal delineated from the “core” metal with atomic sharpness opens the door to a multitude of surface-driven materials properties that can be tuned. However, in practice, such architectures are difficult to retain due to the entropic cost of a segregated near-surface architecture, and the core and surface atoms inevitably mix through interdiffusion over time. We present here a systematic study of interdiffusion in a Pt on Au core–shell architecture and the role of an interrupting single layer of graphene sandwiched between them. The physical and chemical structure of the (near)surface is probed via mean-free-path tuned X-ray photoelectron spectroscopy, high-resolution transmission electron microscopy (HRTEM), and electrochemistry (the oxygen reduction reaction, ORR). We find that at operating temperatures above 100 °C, there is potential for interdiffusion to occur between the primary and support metals of the core–sh...

Abstract: In this study, electroless-plating of a nickel-phosphor (Ni–P) thin film on surface-controlled thermoelectric elements was developed to significantly increase the bonding strength between Bi–Te materials and copper (Cu) electrodes in thermoelectric modules. Without electroless Ni–P plating, the effect of surface roughness on the bonding strength was negligible. Brittle SnTe intermetallic compounds were formed at the bonding interface of the thermoelectric elements and defects such as pores were generated at the bonding interface owing to poor wettability with the solder. However, defects were not present at the bonding interface of the specimen subjected to electroless Ni–P plating, and the electroless Ni–P plating layer acted as a diffusion barrier toward Sn and Te. The bonding strength was higher when the specimen was subjected to Ni–P plating compared with that without Ni–P plating, and it improved with increasing surface roughness. As electroless Ni–P plating improved the wettability with molten solder, the increase in bonding strength was attributed to the formation of a thicker solder reaction layer below the bonding interface owing to an increase in the bonding interface with the solder at higher surface roughness.

Abstract: It is demonstrated that the electric dipole layer due to the overlapping of electron wave functions at the metal/graphene contact results in a negative Fermi-level pinning effect on the region of the GaAs surface with low interface-trap density in the metal/graphene/n-GaAs(001) junction. The graphene interlayer plays the role of a diffusion barrier, preventing the atomic intermixing at the interface and preserving the low interface-trap density region. The negative Fermi-level pinning effect is supported by the decrease of the Schottky barrier with the increase of the metal work function. Our work shows that the graphene interlayer can invert the effective work function of the metal between high and low, making it possible to form both Schottky and Ohmic-like contacts with identical (particularly high work function) metal electrodes on a semiconductor substrate possessing low surface-state density.