Abstract: Abstract Unsatisfied electrode bonding in half-Heusler devices renders thermal damage and large efficiency loss, which limits their practical service at high temperatures. Here, we develop a thermodynamic strategy to screen barrier layer elements. Theoretically, we found that the interface between VIIB elements and half-Heuslers possesses near-zero interfacial reaction energy and large atomic diffusion barrier. Experimentally, such an interphase proves to be the atomic direct bonding and has high thermal stability at 1073 K, leading to ideal ohmic contact. Such thermally inert and ohmic contact interface enable modules stably to work at elevated temperature up to 1100 K, which releases the peak performance of half-Heuslers and in turn boosts the energy conversion efficiencies to the records of 11.1% and 13.3% for half-Heusler single-stage and half-Heusler/Bi 2 Te 3 segmented modules. This design strategy provides a feasible solution for the high-temperature half-Heusler generators and gives enlightenment for other package interconnection design of electronic devices.

Abstract: Realizing high‐temperature thermal stability in thermoelectric (TE) generators is a critical challenge. In this study, a synergistic interface and surface optimization strategy is implemented to enhance Mg3Sb1.5Bi0.5 TE generator performance by employing FeCrTiMnMg thermoelectric interface materials and the MgMn‐based alloy protective coating. The competitive output power density (ω) of 1.7 W cm−2 and a conversion efficiency (η) of 13% for the single‐leg device are achieved at hot‐side temperature (Th) and cold‐side temperature (Tc) of 500 and 5 °C, respectively. An ω of 0.8 W cm−2 and η of 6% for the two‐couple TE devices with p‐type commercial Bi2Te3 are also realized, values that are competitive with the commercial Bi2Te3 device. Additionally, the single‐leg device shows a high stable η for over 100 h when the Th and Tc are 400 and 5 °C, respectively, with an change rate (Δηmax/ηmax,o) of <3%. In situ transmission electron microscopy analysis further reveals that the high stability results from the effectively sluggish interdiffusion and reduced Mg evaporation that decrease the chemical potential gradient, reduce the saturated vapor pressure, and increase the diffusion activation energy barrier. This study provides a general technique route for boosting the high‐temperature thermal stability of TE generator.

Abstract: Atomic layer deposition (ALD) is a suitable technology for conformally depositing thin films on nanometer‐scale 3D structures. RuO2 is a promising diffusion barrier for Ru interconnects owing to its compatibility with Ru ALD and its remarkable diffusion barrier properties. Herein, a RuO2 diffusion barrier using an ALD process is developed. The highly reactive Ru precursor [tricarbonyl(trimethylenemethane)ruthenium] and improved O2 supply enable RuO2 deposition. The optimal process conditions [pulsing time ratio (tO2/tRu): 10, process pressure: 1 Torr, temperature: 180 °C] are established for the RuO2 growth. Growth parameters, such as the growth rate (0.56 Å cycle–1), nucleation delay (incubation period: 6 cycles), and conformality (step coverage: 100%), are also confirmed on the SiO2 substrate. The structural and electrical properties of the Ru/RuO2/Si multilayer are investigated to explore the diffusion barrier performance of the ALD‐RuO2 film. The formation of Ru silicide does not occur without the conductivity degradation of the Ru/RuO2/Si multilayer with an increase in the annealing temperature up to 850 °C, thus demonstrating that interdiffusion of Ru and Si is completely suppressed by a thin (5 nm) ALD‐RuO2 film. Consequently, the practical growth behavior and diffusion barrier performance of RuO2 can serve as a potential diffusion barrier for Ru interconnects.

Abstract: Two-dimensional (2D) materials with a penta-atomic-configuration, such as penta-graphene and penta-B2C, have received great attention as anodes in Li-ion batteries (LIBs). Recently, penta-BCN has been demonstrated to exhibit the highest theoretical capacity to date of 2183 mA h g-1, corresponding to the composition Li3BCN. Herein, we study the layer-by-layer Li adsorption on penta-BCN by explicitly and comprehensively considering its structure. We discover a new, more energetically favorable Li adsorption site that is distinct from the latest report by Chen et al. (Phys. Chem. Chem. Phys., 2021, 23, 17693). The possible migration pathway and the accompanying activation energy are also investigated. Full lithium adsorption leads to the formula Li2BCN and the reduced theoretical capacity of 1455 mA h g-1. Still, penta-BCN exhibits metallic conductivity during Li adsorption, and has a low open-circuit voltage, and a low ion-diffusion barrier, all being beneficial for anode materials. These observations imply that penta-BCN remains one of the most effective anode materials for LIBs with a quick charge/discharge rate.

Abstract: To promote the application of two-dimensional transition metal MXenes in Na-ion batteries, it is essential to expand the MXene family and figure out the mechanism. Density functional theory is employed to predict the performance of different subgroups of transition metal Ti-based MXenes Ti2MC2O2 and M2TiC2O2 (M represents early transition metals from the IIIB–VIB group including V, Cr, Y, Zr, and Nb) as anode materials of Na-ion batteries. Among them, we focused on eight stable MXenes, including Ti2VC2O2, Ti2YC2O2, Ti2ZrC2O2, Ti2NbC2O2, V2TiC2O2, Cr2TiC2O2, Zr2TiC2O2, and Nb2TiC2O2 compared with common Ti3C2 MXene. Ti2ZrC2O2, Zr2TiC2O2, and Nb2TiC2O2 bimetallic MXenes possess a stronger ability to adsorb Na and lower Na diffusion barriers than Ti3C2 MXene. Moreover, the OCV values of Ti2ZrC2O2 and Zr2TiC2O2 MXenes are unique: the value decreases as the number of Na decreases at low Na coverage during discharge, implying that the assembled batteries have a higher energy density than those from Ti3C2 MXene. Furthermore, Zr in Zr2TiC2O2 has a stronger adsorption capacity for Na, and the interaction of Zr atoms with O is also beneficial. Zr2TiC2Tx MXene is expected to be prepared through experiments accompanying a larger capacity (Zr2TiC2O2Na4), better rate performance (diffusion barrier with 0.101 eV), and lower OCV (about 1 V). This finding can provide a reference for future theoretical studies and material selection in experiments on bimetallic MXenes used for Na-ion batteries.

Abstract: A reliable method for preparing a conformal amorphous carbon (a‐C) layer with a thickness of 1‐nm‐level, is tested as a possible Cu diffusion barrier layer for next‐generation ultrahigh‐density semiconductor device miniaturization. A polystyrene brush of uniform thickness is grafted onto 4‐inch SiO2/Si wafer substrates with “self‐limiting” chemistry favoring such a uniform layer. UV crosslinking and subsequent carbonization transforms this polymer film into an ultrathin a‐C layer without pinholes or hillocks. The uniform coating of nonplanar regions or surfaces is also possible. The Cu diffusion “blocking ability” is evaluated by time‐dependent dielectric breakdown (TDDB) tests using a metal−oxide−semiconductor (MOS) capacitor structure. A 0.82 nm‐thick a‐C barrier gives TDDB lifetimes 3.3× longer than that obtained using the conventional 1.0 nm‐thick TaNx diffusion barrier. In addition, this exceptionally uniform ultrathin polymer and a‐C film layers hold promise for selective ion permeable membranes, electrically and thermally insulating films in electronics, slits of angstrom‐scale thickness, and, when appropriately functionalized, as a robust ultrathin coating with many other potential applications.

Abstract: Layer-by-layer graphene growth is demonstrated by repeating CVD growth cycles directly on sapphire substrates. Improved field-effect mobility values are observed for the bottom-gate transistors fabricated by using the bilayer graphene channel, which indicates an improved crystallinity is obtained after the second CVD growth cycle. Despite the poor wettability of copper on graphene surfaces, graphene may act as a thin and effective diffusion barrier for copper atoms. The low resistivity values of thin copper films deposited on thin monolayer MoS2/monolayer graphene heterostructures have demonstrated its potential to replace current thick liner/barrier stacks in back-end interconnects. The unique van der Waals epitaxy growth mode will be helpful for both homo- and heteroepitaxy on 2D material surfaces.

Abstract: Thin Copper (Cu) films (15 nm) are deposited on different 2D material surfaces through e-beam deposition. With the assist of van der Waals epitaxy growth mode on 2D material surfaces, preferential planar growth is observed for Cu films on both MoS2 and WSe2 surfaces at room temperature, which will induce a polycrystalline and continuous Cu film formation. Relative low resistivity values 6.07 (MoS2) and 6.66 (WSe2) μΩ-cm are observed for the thin Cu films. At higher growth temperature 200 °C, Cu diffusion into the MoS2 layers is observed while the non-sulfur 2D material WSe2 can prevent Cu diffusion at the same growth temperature. By further increasing the deposition rates, a record-low resistivity value 4.62 μΩ-cm for thin Cu films is observed for the sample grown on the WSe2 surface. The low resistivity values and the continuous Cu films suggest a good wettability of Cu films on 2D material surfaces. The thin body nature, the capability to prevent Cu diffusion and the unique van der Waals epitaxy growth mode of 2D materials will make non-sulfur 2D materials such as WSe2 a promising candidate to replace the liner/barrier stack in interconnects with reducing linewidths.