Abstract: Density functional theory (DFT) calculations were employed to probe the feasibility of 2D α-CM (M = N, P) as an anode material for Li-ion batteries (LIBs). Our findings demonstrate the dynamical, mechanical and thermal stability of 2D α-CM. In particular, for the 2D α-CP adsorbed with Li atom, binding energy (EB) of −2.00 eV ensures favourable adsorption. In contrast to 2D α-CP, the EB of adsorbed Li atom over α-CN is lower than the cohesive energy of lithium metal, this eliminates the accessibility of 2D α-CN as an anode in LIBs. The Li atom adsorption changes the nature of the 2D α-CP from semiconducting to metallic, ensuring high electronic conductivity. Both partial density of states and Lo¨wdin charge analysis indicate substantial charge transfer from Li atom to 2D α-CP after adsorption. The multilayer adsorption on both sides of 2D α-CP yields Li5.0CP monolayer with remarkably high specific storage capacity (1108.91 mAhg−1). The obtained average open circuit voltage is suitable for extensive battery application. Diffusion barrier of 0.11 eV shows ultrahigh ionic mobility over the 2D α-CP and thus facilitates charging/discharging process. As a result, high specific storage capacity, lower diffusion barrier, negligible volume change and excellent electronic conductivity imply the promising utility of 2D α-CP as anodic material in LIBs.

Abstract: To develop quick‐charge sodium‐ion battery, it is significant to optimize insertion‐type anode to afford fast Na+ diffusion rate and excellent electron conductivity. First‐principles calculations reveal the TiO subcompound superiority for Na+ diffusion following Ti(II)O > Ti(III)O > Ti(IV)O. Hence, in situ growth of amorphous TiO subcompounds with rich oxygen defects based on Ti3C2Tx‐MXene is developed. Meanwhile, the composite presents expanded MXene interlayer spacing and much enhanced conductivity. The synergistic effect of enhanced electron/ion conduction gives a high capacity of 107 mAh g−1 at 50 A g−1, which gives 50% and 150% increasements compared with one counterpart without valence adjustment and another one without MXene expansion. It only needs 20 s (at 30 A g−1) to complete the discharge/charge process and obtains a capacity of 144.5 mAh g−1, which also shows a long‐term cycling stability at quick‐charge mode (121 mAh g−1 after 10000 cycles at 10 A g−1). The enhanced performance comes from fast electron transfer among TiO subcompounds contributed by rich‐defect amorphous TiO2–x, and a reversible change of elastic MXene with interlayer spacing between 1.4 and 1.9 nm during Na+ insertion/extraction process. This study provides a feasible route to boost the kinetics and develop quick‐charge sodium‐ion battery.

Abstract: Electrode contact interfaces for practical thermoelectric (TE) devices require high bonding strength, low specific contact resistivity, and superb stability. Herein, the state-of-the-art Cu2MgFe/Mg2Sn0.75Ge0.25 interface is designed for Mg2Sn0.75Ge0.25-based TE devices, adhering to the general strategy of high bonding propensity, thermal expansion matching, diffusion passivation, and dopant inactivation. The interfacial stability is verified by the in situ transmission electron microscopy analysis, thereby confirming the contributions from decreasing the chemical potential gradient and increasing the diffusion activation energy barrier. The single-leg device exhibits a high power density (ωmax) of 2.6 W cm−2 and conversion efficiency (ηmax) of 8% under a temperature difference (ΔT) of 370 °C, which is the record-breaking value in comparison to other Mg2(Si, Ge, Sn)-based TE devices. Additionally, a two-couple device with p-type Bi2Te3 shows an excellent ωmax of 1.3 W cm−2 and ηmax of 5.4% under a ΔT of 270 °C, comparable to commercial Bi2Te3 devices. The proposed interface design strategy provides a general technique for constructing high-performance devices using cutting-edge TE materials.

Abstract: The cyclic and early isothermal oxidation behaviors at 1050 °C of the NiCoCrAlY, Pt-modified NiCoCrAlY and Pt-modified NiCoCrAlY with Re-based diffusion barrier (DB) have been evaluated. The atomic immigration and electron location function (ELF) at the Ni-Re interface were simulated by density function theory (DFT) calculations. After isothermal oxidation for 1 h, island NiCoCrAlY particles with extremely poor Al were observed in the oxide scale of normal NiCoCrAlY coating, and then the oxide scale transformed into a double-layer structure after oxidation for 20 h. The initial “island-oxide” scale model was proposed to illustrate the oxidation mechanisms for normal NiCoCrAlY coating. The oxide scale of Pt-modified NiCoCrAlY coating was single-layer Al2O3 with rapid coverage at the surface, because the modification of Pt changed the initial oxidation mechanism by promoting the uphill diffusion of Al. The Re-based DB reduced the thickness of the secondary reaction zone (SRZ) by inhibiting the element interdiffusion between the NiCoCrAlY coating and the substrate, thus the Pt-modified NiCoCrAlY with Re-based DB exhibited the lowest interdiffusion extent. Interestingly, the thermal stability of Re-based DB in NiCoCrAlY coating system was poorer than that in NiCrAlY system. The DFT simulation shows that the incorporation of Co made the energy difference more negative, which confirmed that Co promoted the diffusion of Re in the NiCoCrAlY coating, thus accelerating the degradation of Re-based DB.

Abstract: Beta gallium oxide (β-Ga2O3) shows significant promise in high-temperature, high-power, and sensing electronics applications. However, long-term stable metallization layers for Ohmic contacts at high temperatures present unique thermodynamic challenges. The current most common Ohmic contact design based on 20 nm of Ti has been repeatedly demonstrated to fail at even moderately elevated temperatures (300–400 °C) due to a combination of nonstoichiometric Ti/Ga2O3 interfacial reactions and kinetically favored Ti diffusion processes. Here, we demonstrate stable Ohmic contacts for Ga2O3 devices operating up to 500–600 °C using ultrathin Ti layers with a self-limiting interfacial reaction. The ultrathin Ti layer in the 5 nm Ti/100 nm Au contact stack is designed to fully oxidize while forming an Ohmic contact, thereby limiting both thermodynamic and kinetic instability. This novel contact design strategy results in an epitaxial conductive anatase titanium oxide interface layer that enables low-resistance Ohmic contacts that are stable both under long-term continuous operation (>500 h) at 600 °C in vacuum (≤10−4 Torr), as well as after repeated thermal cycling (15 times) between room temperature and 550 °C in flowing N2. This stable Ohmic contact design will accelerate the development of high-temperature devices by enabling research focus to shift toward rectifying interfaces and other interfacial layers.

Abstract: In this work, the deposition of titanium nitride (TiN) thin film using direct current (DC) sputtering technique and its application as diffusion barriers against copper interconnect was presented. The deposited film was analyzed by using X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), and X-ray photoelectron spectroscopy (XPS) techniques. XRD patterns showed the face-centered cubic (FCC) structure for the TiN/SiO2/Si film, having (111) and (200) peaks and TiN (111), Cu(111), and Cu(200) peaks for Cu/TiN/SiO2/Si film. FESEM images revealed that the grains were homogeneously dispersed on the surface of the TiN film, having a finite size. XPS study showed that Ti2p doublet with peaks centered at 455.1 eV and 461.0 eV for TiN film was observed. Furthermore, the stoichiometry of the deposited TiN film was found to be 0.98. The sheet resistance of the TiN film was analyzed by using a four-point probe method, and the resistivity was calculated to be 11 μΩ cm. For the utilization, TiN film were tested for diffusion barrier performance against Cu interconnect. The results exhibited that TiN film has excellent performance in diffusion barrier for copper metallization up to a temperature of 700 °C. However, at a higher annealing temperature of 800 °C, the formation of Cu3Si and TiSi2 compounds were evident. Thus, stoichiometric TiN film with high thermal stability and low resistivity produced in this study could be applied for the fabrication of microelectronic devices.

Abstract: Lead-free inorganic copper-silver-bismuth-halide materials have attracted more and more attention due to their environmental friendliness, high element abundance, and low cost. Here, we developed a strategy of one-step gas-solid-phase diffusion-induced reaction to fabricate a series of bandgap-tunable CuaAgm1Bim2In/CuI bilayer films due to the atomic diffusion effect for the first time. By designing and regulating the sputtered Cu/Ag/Bi metal film thickness, the bandgap of CuaAgm1Bim2In could be reduced from 2.06 to 1.78 eV. Solar cells with the structure of FTO/TiO2/CuaAgm1Bim2In/CuI/carbon were constructed, yielding a champion power conversion efficiency of 2.76%, which is the highest reported for this class of materials owing to the bandgap reduction and the peculiar bilayer structure. The current work provides a practical path for developing the next generation of efficient, stable, and environmentally friendly photovoltaic materials.

Abstract: Na-ion batteries (NIBs) have attracted a great deal of attention for large-scale electric energy storage due to their inherent safety, natural abundant resources, and low cost. The exploration of suitable anode materials is the major challenge in advancing NIB technology. On the basis of first-principles calculations, we systematically explore the potential performance of two-dimensional (2D) TiCl2 as an electrode material for NIBs. Monolayer TiCl2 can be easily exfoliated from the bulk structure with a small exfoliation energy of 0.64 J m-2. It shows good stability, as demonstrated by its high cohesive energy, positive phonon modes, and high thermal stability. Monolayer TiCl2 has high storage capacity (451.3 mA h g-1), low diffusion energy barrier (0.02-0.14 eV), moderate average open-circuit voltage (0.81 V), and small lattice change (2.37%). Moreover, bilayer TiCl2 can significantly enhance the Na adsorption strength but reduce the Na-ion diffusion ability. These results suggest that TiCl2 is a promising anode candidate for NIBs.

Abstract: This study suggests a Ru/ZnO bilayer grown using area-selective atomic layer deposition (AS-ALD) as a multifunctional layer for advanced Cu metallization. As a diffusion barrier and glue layer, ZnO is selectively grown on SiO2 , excluding Cu, where Ru, as a liner and seed layer, is grown on both surfaces. Dodecanethiol (DDT) is used as an inhibitor for the AS-ALD of ZnO using diethylzinc and H2 O at 120 °C. H2 plasma treatment removes the DDT adsorbed on Cu, forming inhibitor-free surfaces. The ALD-Ru film is then successfully deposited at 220 °C using tricarbonyl(trimethylenemethane)ruthenium and O2 . The Cu/bilayer/Si structural and electrical properties are investigated to determine the diffusion barrier performance of the bilayer film. Copper silicide is not formed without the conductivity degradation of the Cu/bilayer/Si structure, even after annealing at 700 °C. The effect of ZnO on the Ru/SiO2 structure interfacial adhesion energy is investigated using a double-cantilever-beam test and is found to increase with ZnO between Ru and SiO2 . Consequently, the Ru/ZnO bilayer can be a multifunctional layer for advanced Cu interconnects. Additionally, the formation of a bottomless barrier by eliminating ZnO on the via bottom, or Cu, is expected to decrease the via resistance for the ever-shrinking Cu lines.

Abstract: The optical performance of low-bilayer-thickness metallic multilayers (ML) can be improved significantly by limiting the intermixing of consecutive layers at the interfaces. Barrier layers are supposed to exhibit a decisive role in controlling diffusion across the interfaces. The element-specific grazing incidence extended X-ray absorption fine structure technique using synchrotron radiation has been used in conjunction with grazing incidence X-ray reflectivity and diffuse X-ray scattering measurements to study the impact of the two most common barrier layers, viz., C and B4C, at the interfaces of Cr/Sc MLs. The diffusion propagation is reduced by both the barrier layers; however, it is found that the improvement is more significant with the B4C barrier layer. It is seen that C forms an intermixed layer with Sc and leads to carbide formation at the interface, which then acts as shielding and prevents further interdiffusion, while B4C hardly penetrates into Sc and stops the overlap between Sc and Cr directly by wetting the corresponding interface. Thus, the above measurements reveal crucial and precise information regarding the elemental diffusion kinetics at the interfaces of Cr/Sc MLs in a non-destructive way, which is very important for technological applications of these MLs as X-ray optical devices.