Interfacial Conductance Research Articles

Structure and magnetic properties of an amine-templated one-dimensional cobalt-fluoro-sulfate containing Co4F4 cubane and hydrogen evolution reaction (HER) performance of its derived carbon-wrapped CoSe2 nanorods.

Amine-templated 1D cobalt fluoro sulfate of the composition [(CH3)2NH2]2[Co4F4(SO4)3(C3N2H4)4], consisting of Co4F4 cubane-type secondary building unit, has been synthesized under solvothermal condition. The magnetic properties of the Co4F4 cubane chain exhibited a low-temperature magnetic ordering below 17 K (Tc) attributed to intra-cluster ferromagnetic coupling and did not show spin-glass freezing. The selenylation of the Co4F4 cubane chain leads to the formation of sphere-like CoSe2 in the hydrothermal route (CoSe2@HT). At the same time, nanorods of CoSe2 encapsulated with carbon matrix were obtained in a sealed tube method (CoSe2@ST). Moreover, CoSe2@ST exhibited a higher hydrogen evolution reaction (HER) activity than CoSe2@HT in an acidic medium with 177 mV overpotential to achieve the benchmark current density of 10 mA cm-2. The promising HER performance of derived CoSe2@ST could be attributed to an increase in the geometrical and specific activity due to the encapsulation of N-doped carbon matrix over the CoSe2 nanorods that facilitate faster charge transfer at the electrode-electrolyte interface and higher electrochemical conductivity than the derived CoSe2@HT. This work demonstrates a low-temperature, solvent- and reducing agent-free new synthetic approach for synthesizing framework-derived materials.

Alleviation of Self-Heating Effect in Top-Gated Ultrathin In2O3 FETs Using a Thermal Adhesion Layer

In this work, a thin layer of hexagonal boron nitride (h-BN) or HfO2 serves as an adhesion layer between the ultrathin atomic-layer-deposited (ALD) indium oxide (In2O3) channel and a sapphire substrate to enhance the thermal interfacial conductance. A thermo-reflectance (TR) measurement system with high spatial resolution is introduced to experimentally demonstrates the improvement. With the thin h-BN or HfO2 interlayer, the temperature elevation ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\Delta {T}$ </tex-math></inline-formula> ) induced by self-heating effect (SHE) is decreased by roughly 9% or 27%, respectively. To quantify the improvement of the interfacial heat transfer, a steady-state thermal diffusion model with a finite-element method is combined with the experimental TR observation to extract the effective thermal boundary conductance (TBC) values in each case. It is shown that the effective TBC is ameliorated by a factor of 2 or 7 with the h-BN or HfO2 interlayer, which is responsible for the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\Delta {T}$ </tex-math></inline-formula> reduction. Furthermore, phonon density of states (PDOS) distribution mismatch implies that the intersection over union (IOU) ratio in the acoustic phonon region of In2O3 with h-BN or HfO2 is roughly 3 or 11 times higher than that directly with sapphire, which is responsible for the profound TBC enhancement. Based on this, ultrahigh maximum drain current of 2.4 mA/ <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu \text{m}$ </tex-math></inline-formula> is achieved with 2.1-nm-thick In2O3 channel on a sapphire substrate with an HfO2 interlayer in between due to the alleviated SHE.

Droplets Patterning of Structurally Integrated 3D Conductive Networks-Based Flexible Strain Sensors for Healthcare Monitoring.

Flexible strain sensors with significant extensibility, stability, and durability are essential for public healthcare due to their ability to monitor vital health signals noninvasively. However, thus far, the conductive networks have been plagued by the inconsistent interface states of the conductive components, which hampered the ultimate sensitivity performance. Here, we demonstrate structurally integrated 3D conductive networks-based flexible strain sensors of hybrid Ag nanorods/nanoparticles(AgNRs/NPs) by combining a droplet-based aerosol jet printing(AJP) process and a feasible transfer process. Structurally integrated 3D conductive networks have been intentionally developed by tweaking droplets deposition behaviors at multi-scale for efficient hybridization and ordered assembly of AgNRs/NPs. The hybrid AgNRs/NPs enhance interfacial conduction and mechanical properties during stretching. In a strain range of 25%, the developed sensor demonstrates an ideal gauge factor of 23.18. When real-time monitoring of finger bending, arm bending, squatting, and vocalization, the fabricated sensors revealed effective responses to human movements. Our findings demonstrate the efficient droplet-based AJP process is particularly capable of developing advanced flexible devices for optoelectronics and wearable electronics applications.

Hybrid Electrolyte of Li1.3Al0.3Ti1.7(PO4)3 Nanofibers and Cross-linked Gel Electrolyte for Li Metal Batteries

Hybrid solid electrolytes (HSEs) based on oxide-based inorganic electrolytes in combination with polymer electrolytes or gel electrolytes are promising options for lithium batteries. Utilizing the synergistic combination of the two materials, HSEs offer great potential to achieve high ionic conductivity, reduced interfacial resistance, mechanical integrity, and high processability. Despite the enhanced performances by the hybrid designs, the reason for the enhancement has not been fully understood. Herein, we report an HSE consisting of a three-dimensional (3D) network of Li1.3Al0.3Ti1.7(PO4)3(LATP) nanofibers and a UV-cured gel electrolyte in comparison with an LATP powder-dispersed and an LATP-free UV-curved gel electrolyte to elucidate the role of the 3D LATP network in enhancing the performance of lithium metal batteries. The LATP fiber was prepared by electrospinning LATP powder and polyacrylonitrile without calcination. The incorporation of the LATP fiber network to the gel electrolyte increases the ionic conductivity and Li+ transference number due to the interfacial Li+ conduction between the fibers and the gel electrolyte. The LATP fiber and powder-dispersed gel electrolytes show a change in the SEI structure; however, the former exhibits a more uniform Li deposition morphology, longer cycling stability, and higher rate capability, demonstrating the critical role of the interfacial conduction.

Role of Cu2O surface terminations on interface conductivity with graphene

Two-dimensional materials and their interfaces with functional oxides have increasing applications in optoelectronic devices. Cu2O is an important functional oxide and efficient charge transport across the Cu2O/contact material interface is a significant bottleneck in the development of efficient optoelectronic devices. Here, we investigate the electronic properties of graphene, a transparent contact material, interface with intrinsic (100) Cu2O thin films using first principles calculations. From the graphene-Cu2O heterojunction interface, we observe that despite the Cu2O surface termination and electronegativity order of the atoms involved, the physisorbed graphene layer is always electron depleted. The graphene heterojunction with the reconstructed Copper terminated surface shows a covalent character, a smaller tunnel barrier and blocking Schottky potential of 0.19 eV for holes. In contrast, the reconstructed oxygen terminated structure shows an ionic character, a significantly taller tunnel barrier and a transparent ohmic contact for holes. These results show that graphene is an attractive transparent contact material for Cu2O based hole transport layers in photovoltaics, chemical and photon sensing, and energy storage.

Asymmetric potential barrier lowering promotes photocatalytic nonoxidative dehydrogenation of anhydrous methanol

Photocatalytic nonoxidative dehydrogenation of anhydrous methanol can be a promising approach to producing formaldehyde and hydrogen as it can avoid catalyst degradation occurred at high temperature in conventional catalysis. To facilitate the rate-determining step, we propose to lower the barrier height for semiconductor-cocatalyst interfacial electron transfer by solution acidity modulating, which shifts electroreduction potential and inherently lowers the interface conduction band position. Since this measure does not change the surface conduction band position, the increase in protons does not aggravate leakage of electron from semiconductor. The resulted asymmetric potential barrier lowering endows photocatalyst with larger driving force for enhancing utilization of photogenerated charge carriers. In our demonstrated reaction, a quantum yield of 89.9 % with formaldehyde selectivity of 95.5 % can be realized.

Designing High Interfacial Conduction beyond Bulk via Engineering the Semiconductor-Ionic Heterostructure CeO2-δ/BaZr0.8Y0.2O3 for Superior Proton Conductive Fuel Cell and Water Electrolysis Applications.

Proton ceramic fuel cells (PCFCs) are an emerging clean energy technology; however, a key challenge persists in improving the electrolyte proton conductivity, e.g., around 10-3-10-2 S cm-1 at 600 °C for the well-known BaZr0.8Y0.2O3 (BZY), that is far below the required 0.1 S cm-1. Herein, we report an approach for tuning BZY from low bulk to high interfacial conduction by introducing a semiconductor CeO2-δ forming a semiconductor-ionic heterostructure CeO2-δ/BZY. The interfacial conduction was identified by a significantly higher conductivity obtained from the BZY grain boundary than that of the bulk and a further improvement from the CeO2-δ/BZY which achieved a remarkably high proton conductivity of 0.23 S cm-1. This enabled a high peak power of 845 mW cm-2 at 520 °C from a PCFC using the CeO2-δ/BZY as the electrolyte, in strong contrast to the BZY bulk conduction electrolyte with only 229 mW cm-2. Furthermore, the CeO2-δ/BZY fuel cell was operated under water electrolysis mode, exhibiting a very high current density output of 3.2 A cm-2 corresponding to a high H2 production rate, under 2.0 V at 520 °C. The band structure and a built-in-field-assisted proton transport mechanism have been proposed and explained. This work demonstrates an efficient way of tuning the electrolyte from low bulk to high interfacial proton conduction to attain sufficient conductivity required for PCFCs, electrolyzers, and other advanced electrochemical energy technologies.

Reactive MnO2 template-assisted synthesis of double-shelled PPy hollow nanotubes to boost microwave absorption

Microwave absorbing materials (MAMs) with wide effective absorption bandwidth (EAB) and low filling ratio are highly desirable for practical applications. Rational design in components and structures is one of the effective strategies to achieve MAMs with high performance. Herein, double-shelled hollow (DSH) polypyrrole (PPy) nanotubes were synthesized with hydrochloric acid (HCl) and sodium p-styrene sulfonate (SS) co-doping polymerization process using manganese dioxide (MnO2) nanorods as a self-sacrifice template. With the increase of HCl concentration, the 1D MnO2 core diminishes gradually to form the MnO2@PPy coaxial nanostructures and finally the DSH PPy nanotube, which tunes the microwave absorption performance. Importantly, the DSH PPy nanotubes exhibit excellent microwave absorption of an optimal reflection loss of –50.4 dB and a wide EAB of 7.7 GHz with a low filling ratio of 5 wt% in a paraffin wax matrix. The excellent microwave absorption is believed to be mainly attributed to the enhanced synergistic effects of interfacial polarization and conduction loss arising from the unique DSH structure and the co-doping polymerization.

Charge-transfer interface of insulating metal-organic frameworks with metallic conduction

Downsizing materials into hetero-structured thin film configurations is an important avenue to capture various interfacial phenomena. Metallic conduction at the interfaces of insulating transition metal oxides and organic molecules are notable examples, though, it remained elusive in the domain of coordination polymers including metal-organic frameworks (MOFs). MOFs are comprised of metal centers connected to organic linkers with an extended coordination geometry and potential void space. Poor orbitals overlap often makes these crystalline solids electrical insulators. Herein, we have fabricated hetero-structured thin film of a Mott and a band insulating MOFs via layer-by-layer method. Electrical transport measurements across the thin film evidenced an interfacial metallic conduction. The origin of such an unusual observation was understood by the first-principles density functional theory calculations; specifically, Bader charge analysis revealed significant accumulation and percolation of charge across the interface. We anticipate similar interfacial effects in other rationally designed hetero-structured thin films of MOFs.

Properties of NbC/а‐C:H films on titanium bipolar plates for proton exchange membrane fuel cells

AbstractSurface modification of metallic bipolar plates is a crucial subject for the performance elevation of proton exchange membrane fuel cells (PEMFCs). In this work, a series of NbC/а‐C:H films with different Nb/C ratios are prepared by arc ion plating. Film microstructure, composition, mechanical properties, hydrophobility, interfacial contact resistance (ICR), and corrosion resistance in the simulated cathode environment of PEMFCs are systematically studied. The results show that within the experiment conditions, higher NbC content helps to promote the film hardness and adhesion strength as well as the interfacial conductivity. While higher а‐C:H content attributes to a more compact microstructure thus improving the anti‐corrosion performance. The best corrosion resistance and conductivity come with the lowest corrosion current density of 0.09 µA/cm2 and ICR of 0.77 mΩ cm2, respectively. Based on the result of this research, to further improve the comprehensive performance of NbC/а‐C:H film, strategies for increasing the metal carbide content and preventing surface metal oxidation while keeping a dense and fine microstructure need to be considered.

Ni nanospheres coated with tunable carbon shells for dielectric-controlled superior electromagnetic wave absorbing

To obtain high-efficiency electromagnetic wave absorbing (EMA) material with strong reflection loss ( RL ) and wide effective absorbing bandwidth (EAB), Ni particles are successfully prepared in this work by a liquid phase reduction approach, and Ni@C is subsequently designed and fabricated through combined polymerization and carbonization process. The pristine Ni exhibits outstanding EMA performances in middle- and high-frequency with a maximum RL ( RL max ) of 62.3 dB (2.3 mm) at K u band and an EAB of 10.9 GHz (5.6–16.5 GHz) at 3.0 mm, covering 75% K u (12–18 GHz), 100% X (8–12 GHz) and 60% C (4–8 GHz) band. Such a superior property is attributed to the dielectric losses derived from interface polarization, dipole polarization and conduction loss, along with magnetic losses comes from natural and exchange resonance. An introducing of carbon shell with manipulated thicknesses induces positive enhancement in dielectric losses. Meanwhile, core-shell structures enable multiple scattering and reflection of microwaves. Thus, Ni@C spheres exhibit significantly enhanced EMA performances in low-frequency covering S (2–4 GHz) and C band with an RL max at 4.4 GHz reaching 64.4 dB (Ni@C-0.4) and an RL max at 2.6 GHz reaching 59.3 dB (Ni@C-0.6). Therefore, Ni and Ni@C demonstrate a unique blend of favorable EMA performances, which are promising for next-generation intelligent EMA systems.

Atomistic insights into the heat conductance across the interfaces between erythritol and different metals: A non-equilibrium molecular dynamics study

The heat conductance across the interface between a phase change material (PCM) and the metal shell is important for thermal design of latent heat storage systems. Non-equilibrium molecular dynamics simulations were carried out in this work to unravel, at the atomistic level, the interfacial heat conductance mechanisms between erythritol (the most promising medium-temperature polyol PCM) and two different metals (i.e., copper and aluminum). The interfacial contact ratio was introduced as a parameter to represent different contact conditions at the interfaces, for example, different surface roughness levels of the metals. It was found that with the increase of interfacial contact ratio, the temperature difference between the erythritol/metal interfaces decreases, whereas the interfacial heat transfer coefficient increases gradually. At the perfect contact condition, i.e., the interfacial contact ratio reaches 100%, the interfacial heat transfer coefficients across the erythritol/Cu and erythritol/Al interfaces were predicted to be 398 ± 26 MW/m2K and 544 ± 11 MW/m2K, respectively. The interfacial heat conductance of erythritol/Al is better than that of erythritol/Cu. The mismatch of atomic spectral density across the interfaces between erythritol and the two metals was analyzed and distinguished. These results could guide the selection of packaging materials and the thermal design of erythritol-based latent heat storage systems.

Surface and interfacial conduction using gadolinium-doped ceria electrolyte for advanced low temperature 400–500 °C fuel cell

Lowering the operating temperature with enhanced performance and better efficiency is considered a universal R&D bottleneck for the progress of low-temperature (<520 °C) solid oxide fuel cells (SOFCs) or ceramic fuel cells (CFCs) to avail the opportunities of commercialization. Bulk doping is the primary ionic conduction mechanism in traditional electrolyte materials for CFC, mainly influenced by the operating temperature and bulk density, thus resulting in high operational temperature. Herein, we proposed a new mechanism for tunning Ce0.9Gd0.1O2-δ (GDC) electrolyte based on a nanocrystalline structure from surface or grain boundary conduction to interfacial conduction by introducing the carbonates to form the heterostructure, exhibiting an extremely high ionic conductivity of (0.2 S·cm−1) at 520 °C. At first, we noticed that the grain boundary conduction of GDC is causing to enhance the charge carrier leading to establishing surface conduction. We further modify the GDC with carbonates to form the core–shell heterostructure to boost ionic conduction. The constructed cell with core–shell heterostructure has exhibited a remarkable performance of 968 mW/cm2.In contrast, 578 mW/cm2 was achieved from the surface conduction of GDC, and at the same time, we observed immensely low grain-boundary resistance from the impedance analysis. The mechanism of core–shell structure formation has been discussed in detail, and the ionic conduction at the surface and interfaces can be considered the dominant conduction mechanism for GDC electrolytes. This work has explored a new approach by tuning the ionic property from surface to interface to develop advanced CFCs, significantly improving the state-of-art GDC electrolyte via enhancing surface/interface conductions. This may be developed as a more functional approach for advanced energy materials, e.g., battery and electrolysis devices.

Improving the interfacial stability, conductivity, and electrochemical performance of Li2MoO3@g-C3N4 composite as a promising cathode for lithium-ion battery

Li-rich layered Li2MoO3 (LMO) materials are one promising cathode materials for Li-ion batteries due to their high theoretical capacity and without oxygen evolution. However, the poor electrical conductivity and air instability have limited its application as a cathode material for lithium-ion battery. To solve these problems, Li2MoO3/g-C3N4 composites were successfully constructed by combining the molten salt and ball milling methods. Carbon nitride (g-C3N4) with an abundant nitrogen-containing carbon framework contains a large number of “hole” defects and double-bonded nitrogen vacancy edges, which are favorable for the adsorption and diffusion of Li ions. In addition, density functional theory (DFT) calculations revealed that a stable interface can be formed between g-C3N4 and LMO, which also leads to the improvement of the electronic conductivity and the reduction of interfacial impedance of the composite. Therefore, the electrochemical performance of the composite material is significantly improved. The discharge capacity of GLMO-5 at a current density of 1700 mA g−1 is 64.6 mAh/g, which is much greater than the value (29.9 mAh/g) of the original LMO sample under the same conditions. EIS further shows that GLMO-5 has the highest discharge capacity with a DLi+ value of 1.94 × 10−14 cm2 s−1. These results indicate that constructing LMO-based composites with a highly stable layered material containing unsaturated functional groups should be an effective strategy to enhance the interfacial stability, electronic conductivity, and thus the electrochemical performances of the cathode materials.

Highly Improved Efficiency and Stability of 2D Perovskite Solar Cells via Bifunctional Inorganic Salt KPF6 Modified NiOx Hole Transport Layer

In general, improving the electrical conductivity of bare NiO x film and alleviating the undesired energy level mismatch by interface engineering are operative to enhance the property of 2D perovskite solar cells (2D PSCs) based on NiO x . Herein, the NiO x /2D perovskite interface is modified by inorganic salt KPF6 to improve the interfacial contact and conductivity of NiO x . It is revealed that KPF6 not only improves the conductivity of NiO x through the formation of NiF coordination bond with NiO x by PF6‐ but also promotes the energy level matching between NiO x and the 2D perovskite layer. Thus, KPF6‐modified NiO x greatly enhances the extraction ability of hole carriers in 2D perovskite layers and improves the crystallinity of 2D perovskite films. Accordingly, the NiO x /KPF6‐based 2D PSCs attain an optimal power conversion efficiency (PCE) of 14.34%. Meanwhile, the KPF6 modified device without sealed maintains 93% of its original PCE for 600 h on a 60 °C hot plate filled with nitrogen and 72% after aging for 600 h with a humidity of 35 ± 10% in the atmosphere, respectively. This study demonstrates the effectiveness of using inorganic salts to modify NiO x hole transport layers to augment the optoelectronic properties and stability of 2D PSCs.

Self-sacrificial growth of hierarchical P(Ni, Co, Fe) for enhanced asymmetric supercapacitors and oxygen evolution reactions

Highly efficient and environmentally friendly multifunctional electrode materials for application in supercapacitors to electrocatalysis are important for advances in the future of electrical energy storage and green hydrogen production. This work reports a simple growth strategy to obtain hierarchical P(Ni, Co, Fe) modified electrodes by phosphating a core/shell composite of nickel-cobalt (NiCo) Prussian blue analogues fabricated through an in situ self-sacrificial growth process. Due to the unique microstructure, abundant surface-active sites, and enhanced interfacial conductivity, the hybrid electrode exhibits specific capacitance as high as 1125.8 F g −1 (3.7 F cm−2) at 2 mA cm−2, excellent rate capability and improved cycling stability (97.1% retention capacitance after 5000 cycles at 50 mA cm−2 and 89.9% after continuous 5000 cycles at 100 mA cm−2). Furthermore, the hybrid structure shows excellent oxygen evolution reaction performance with an overpotential of 252 mV at 100 mA cm−2 and 283 mV at 300 mA cm−2, with a low Tafel slope of 68 mV dec−1, and overall water splitting abilities with a cell voltage of 1.55 V at 100 mA cm−2. This work provides insights into the design of next-generation high-performance multifunctional electrode materials by controlling the surface/interface of multicomponent structures for enhancing their properties.

In-situ polymerized electrolyte modified with oligomeric cyclotetrasiloxane for all-solid-state lithium metal batteries

High energy density and high-safety is expected for the ongoing revolution of lithium-ion batteries (LIBs). All-solid-state lithium metal batteries (ASSLMBs) are promising to break through the bottleneck of traditional liquid LIBs. However, the huge interfacial resistance between solid electrolytes and cathode is a hinder to the develop ASSLMBs. Herein, we report an in-situ polymerized solid-state electrolytes (SPE) based on oligomeric cyclotetrasiloxane (CTS) and polyethylene glycol diglycidyl ether (PEGDE) to solve this problem. CTS can provide a three-dimensional skeleton for the cross-linked SPE, which can effectively improve the properties of SPE. When the CTS content is 10 wt%, SPE exhibits a high ionic conductivity at 28 °C (0.37 mS cm−1) and a wide electrochemical stable window of 5.02 V (vs Li/Li+). Benefiting from the in-situ polymerization properties, ionic transportation at the cathode/electrolyte interface can be enhanced. Especially, the in-situ SPE exhibits outstanding compatibility against lithium metal over 600 h at a current density of 0.2 mA cm−2, the Li/SPE/LiCoO2 can deliver a capacity of 120.5 mAh g−1 at 0.05 C after 100 cycles. Our study, therefore, provides a new type of SPE to meet both interfacial and bulk conductivity requirements for ASSLMBs.

Enable high reversibility of Fe/Cu based fluoride conversion batteries via interfacial gas release and detergency of garnet electrolytes

Garnet-type Ta-doped Li7La3Zr2O12 (LLZTO) electrolyte suffers from unstable chemical passivation under air exposure, responsible for the poor interfacial wettability and conductivity with Li metal. Instead of conventional methods to remove surface contaminants by mechanical polishing, acid etching and high temperature reduction, herein we propose a simple strategy of interfacial gas release and detergency to smartly convert Li2CO3 passivation layer into ion-conductive Li3PO4 domains at mild temperature (∼200 ℃). The in-situ formation of PH3 vapor and its phosphorization enables a dramatic decrease of Li/garnet interfacial resistance down to 2 Ω cm2 at room temperature (RT). The improved interfacial wettability and conductivity endow the symmetric cells with ultra-stable galvanostatic cycling over 1500 h and high critical current density of 2.6 mA/cm2. The high coulombic efficiency of Li plating enables a high reversibility of solid-state NCM811/Li cells even under a low N/P ratio (∼4) and high cut-off voltage of 4.5 V at RT. The prototype of fluoride-garnet solid-state batteries are successfully driven as rechargeable system (rather than widely known primary battery) with high conversion capacity (400 ∼ 500 mAh/g) and high-rate performance (251.2 mAh/g at 3 C). This interface infiltration-detergency approach provides a practical solution to the achievement of high-energy solid-state Li metal batteries.

Effective spin dynamic control of CoFeB/Nd heterostructure by matched resistivity

The spin dynamics modulation has attracted extensive attention in the past decades. Rare-earth (RE) metals are essential participants in this context due to the large spin–orbit coupling. Here, with neodymium (Nd) capping, we achieve the enhancement on spin dynamic damping of Co40Fe40B20 (CFB) films by three times larger than that of CFB single layer. Based on the spin pumping theory, the interfacial spin mixing conductance Geff↑↓ is calculated as 7.3 × 1015 cm−2, which is one order larger than that of CFB/Pt. It leads to the large spin current transparency at CFB/Nd interface. By comparing of the resistivity of each layer, we found that the matched resistivity at two sides of the CFB/Nd interface plays an important role in the enhancement of Geff↑↓. As a consequence, a high spin transparency of the CFB/Nd interface is obtained as 82%. In addition, damping enhancement of CFB is not changed promptly by inserting 1–2 nm Cu layer, but it is suppressed when the Cu layer is thicker than 3 nm, which is related to the thickness dependence of the Cu resistivity. Our study broadens the horizon for the application of rare-earth (RE) in spintronics.

Influence of interfacial configuration on bonding properties and thermal conductivity of heterogeneous interface in Al/Graphite composite used for electronic packaging

With the purpose of improving the service performance of aluminum(Al)/graphite(Gr) composites used for electronic packaging, the density functional theory (DFT) calculations were employed to investigate the influence of the interfacial configuration on the bonding properties and thermal conductivity of Al/Gr heterogeneous interface. The Al(111)/Gr(0001) interfaces with the low mismatch (0.569%) were first constructed by lattice transformation, and two different interfacial configurations of Top and Bridge were determined. The calculated results indicate that, the interfacial bonding properties of Al(111)/Gr(0001) interfaces are determined by interfacial Al–C bonding behavior. Although the covalent characteristics of Al–C bonds are similar for the two configurations, the ionic characteristics for Top configuration are significantly stronger than Bridge configuration. Therefore, the Top configuration has not only a greater bonding strength than Bridge configuration manifested as the larger interfacial work of adhesion for 0.323 J/m2 and ideal tensile strength of 1.47Gpa, but also the better plasticity with the sustainable maximum strain of 10.46%. Moreover, the thermal conductivity of Top configuration is higher than that of Bridge configuration and the maximum values of the two configurations are 4.90 and 3.75×10−2·W·m−1·k−1, respectively. The mechanism for the favorable thermal transport properties of Top configuration compared to Bridge configuration lies in the high electron density and the large degree of electron delocalization at the interface. Therefore, the Top configuration is the promising Al(111)/Gr(0001) interfacial configuration, which can significantly improve the bonding properties and thermal conductivity of the Al/Gr composite.