Interfacial Layer Research Articles

Rubbing-induced site-selective deposition of 2D material patterns on nanomembranes

2D-layered materials (e.g., graphene and transition metal dichalcogenides) have attracted huge attention due to their unique mechanical and electrical properties. Emerging research efforts, which seek to combine device characterization and high-resolution electron micrography analysis for 2D-layered device features, demand nano/microlithographic techniques capable of producing ordered 2D material patterns on ultrathin membranes with nanoscale thicknesses. However, such membranes are so fragile that most conventional lithographic techniques can be hardly performed on them to generate 2D material patterns. Our previous works have demonstrated that the rubbing-induced site-selective (RISS) deposition method can produce arbitrary 2D semiconductor (e.g., MoS2 and Bi2Se3) patterns on regular device substrates. This fabrication route prevents the vulnerable 2D-layered structures from the detrimental damage introduced by plasma etching and resist-based lithography processes. In this work, we explore the applicability of RISS for directly producing 2D material patterns on nanomembranes. Specifically, this work shows that a polymeric interfacing layer on the rubbing template features, which can effectively prevent stress concentration during the rubbing process, is crucial to successful implementation of RISS processes on nanomembranes. Furthermore, we carried out the mechanics simulation of the Von Mises stress and pressure distribution on the RISS-processed membrane to identify the optimal rubbing load, which can generate sufficient triboelectric charge for material deposition but no damage to the membrane. Using this approach, we have successfully demonstrated the deposition of Bi2Se3 patterns on 25 nm SiOx nanomembranes and high-resolution transmission electron micrography characterization of the crystallographic structures.

Integrating Prelithiation and Interface Protection to Achieve High‐Energy All‐Solid‐State Batteries

All‐solid‐state batteries (ASSBs), particularly those with Li‐free anodes or even anode‐free configurations, have attracted extensive attention due to high safety and energy density. However, chemical‐mechanical degradation typically deteriorates the cycle life and energy of Li‐free anode ASSBs with the absence of Li inventory. Here, the prelithiation agent Li5FeO4 (LFO) coated Ni‐rich layered oxide is developed as the cathode for Li‐free anode ASSBs. The coated LFO acts as an interfacial protective layer to prevent the highly oxidizing Ni‐rich cathode from reacting with sulfide solid‐state electrolytes (SSEs), mitigating the structural degradation of Ni‐rich cathodes and the decomposition of SSE, resulting in excellent cycle life. Beneficial from the coated LFO in the cathode of the Li‐free anode ASSBs, the reversible capacity improves from 174.7 mAh g−1 to 199.7 mAh g−1, and the capacity retention is enhanced from 33.8% to 84.8% after 100 cycles. Additionally, an ultrahigh energy density of 440 Wh kg−1, based on the mass of the composite cathode, Li‐free anode, and SSE, is obtained in a Li‐free anode all‐solid‐state pouch cell equipped with the LFO‐coated cathode.

Integrating Prelithiation and Interface Protection to Achieve High-Energy All-Solid-State Batteries.

All-solid-state batteries (ASSBs), particularly those with Li-free anodes or even anode-free configurations, have attracted extensive attention due to high safety and energy density. However, chemical-mechanical degradation typically deteriorates the cycle life and energy of Li-free anode ASSBs with the absence of Li inventory. Here, the prelithiation agent Li5FeO4 (LFO) coated Ni-rich layered oxide is developed as the cathode for Li-free anode ASSBs. The coated LFO acts as an interfacial protective layer to prevent the highly oxidizing Ni-rich cathode from reacting with sulfide solid-state electrolytes (SSEs), mitigating the structural degradation of Ni-rich cathodes and the decomposition of SSE, resulting in excellent cycle life. Beneficial from the coated LFO in the cathode of the Li-free anode ASSBs, the reversible capacity improves from 174.7 mAh g-1 to 199.7 mAh g-1, and the capacity retention is enhanced from 33.8% to 84.8% after 100 cycles. Additionally, an ultrahigh energy density of 440 Wh kg-1, based on the mass of the composite cathode, Li-free anode, and SSE, is obtained in a Li-free anode all-solid-state pouch cell equipped with the LFO-coated cathode.

Competitive correlation between the interface layers determines the shear strength in Kovar/AgCuTi/Si3N4 joints

AbstractAs a promising high‐thermal‐conductivity ceramics, the direct bonding of Si3N4 with metals remains challenging. Here, we employed active metal brazing of Si3N4 ceramics and Kovar alloys using AgCuTi metal filler, and found that the shear strength in the prepared Kovar/AgCuTi/Si3N4 joints depends on the competitive correlation between the interface layers. The competitive consumption for active element Ti by Kovar/AgCuTi interfacial reactions reduced AgCuTi/Si3N4 interface layer thickness and deteriorated final shear strength, even when using a high‐Ti‐content filler. Surface analysis indicated that interfacial fracture between Ag‐based solid solution and Ti5Si3 was the primary cause of failure. Density functional theory (DFT) revealed that Ag (111)/Fe2Ti (001) interface had higher ideal work of adhesion (Wad) than Ag (111)/Ti5Si3 (001) interface, confirming the importance of AgCuTi/Si3N4 interface layer. Ultimately, by adjusting interface reaction layer thickness, the joints reached a high shear strength of 154.3 MPa.

Effect of post-deposition annealing on crystal structure of RF magnetron sputtered germanium dioxide thin films

In this work, we demonstrate the growth and phase stabilization of ultrawide bandgap polycrystalline rutile germanium dioxide (GeO2) thin films. GeO2 thin films were deposited using RF magnetron sputtering on r-plane sapphire (Al2O3) substrates. As-deposited films were x-ray amorphous. Postdeposition annealing was performed at temperatures between 650 and 950 °C in an oxygen or nitrogen ambient. Annealing at temperatures from 750 to 950 °C resulted in mixed-phase polycrystalline films containing tetragonal (rutile) GeO2, hexagonal (α-quartz) GeO2, and/or cubic (diamond) germanium (Ge). When nitrogen was used as the anneal ambient, mixed GeO2 phases were observed. In contrast, annealing in oxygen promoted stabilization of the r-GeO2 phase. Grazing angle x-ray diffraction showed a preferred orientation of (220) r-GeO2 for all crystallized films. The combination of O2 annealing and O2 flux during growth resulted in r-GeO2 films with highly preferential alignment. Using electron microscopy, we observed an interfacial layer of hexagonal-oriented GeO2 with epitaxial alignment to the (11¯02) Al2O3 substrate, which may help stabilize the top polycrystalline r-GeO2 film.

Highly Efficient Organic/Silicon Hybrid Solar Cells with a MoO3 Capping Layer.

Organic/Si hybrid solar cells have attracted considerable attention for their uncomplicated fabrication process and superior device efficiency, making them a promising candidate for sustainable energy applications. However, the efficient collection and separation of charge carriers at the organic/Si heterojunction interface are primarily hindered by the inadequate work function of poly (3,4-ethylenedioxythiophene): poly (styrenesulfonate) (PEDOT:PSS). Here, the application of a high-work-function MoO3 film onto the n-Si/PEDOT:PSS surface leads to a notable enhancement in the device's built-in potential. This enhancement results in the creation of an inversion layer near the n-Si surface and facilitates charge separation at the interface. Simultaneously, it inhibits charge recombination at the heterojunction interface. As a result, the champion PEDOT:PSS/Si solar cell, which incorporates a MoO3 interface layer, demonstrates an efficiency of 16.0% and achieves a high fill factor of 80.8%. These findings provide a straightforward and promising strategy for promoting the collection and transmission of charge carriers at the interface of photovoltaic devices.

Bifunctional modulation of Li-rich layered oxide cathode material via W-modification for improved electrochemical performance

Lithium-rich layered oxides (LRLOs) have raised the greatest attention to the high-energy-density Li-ion batteries. Nevertheless, the undesirable interfacial side reactions and the structure transformation cause fast voltage fading and poor capacity retention of LRLO cathodes, which extremely prevent their practical application. Surface coating or lattice doping has been an effective strategy to improve its electrochemical properties. However, the general performance of the material can only be limitedly promoted. Herein, we proposed a bifunctional modulation of LRLO cathodes coupled by bulk-phase W-doping and surficial Li2WO4 nanocoating of LRLOs using a facile synchronous lithiation strategy under a high-temperature solid-state treatment. The modified material (2 mol% W6+ modified) showed a distinguished discharge capability of 260.5 mAh/g at 0.1 C after 50 cycles. Meanwhile, a competitive capacity retention of 95.38% at 1 C after 100 cycles was achieved. The splendid electrochemical performance can be the result of the increased interlayer spacing for enhancing Li+ diffusion kinetics and the stronger W–O bond for alleviating oxygen release after W-doping and Li2WO4 nanocoating, which not only accelerates the Li+ transfer rate as its fast Li+ transfer channels but also act as a transitional interface layer to restrain the interfacial adverse reactions.

Crack monitoring and repair model of SMA composite material based on strain transfer

In the process of using composite materials, crack damage is unavoidable. These cracks may cause a decrease in the structural performance of the material and may even pose a threat to the safety of the entire structure. In this paper, the shape memory alloy (SMA) is embedded into the composite material, and the strain transfer effect of the interface layer is considered. The crack monitoring and repair model of SMA composite material based on strain transfer are established using SMA resistance-sensing characteristics and SMA constitutive model. Based on this monitoring and repair model, the crack monitoring behavior of SMA under different initial states and temperature conditions is discussed, and the crack repair behavior of SMA under specific initial states and temperature conditions is also discussed. The research results show that the change in SMA resistance and the strain of the composite material crack are linearly segmented, and as the temperature increases, the composite material crack is gradually repaired. This study can provide theoretical guidance for the further engineering application of SMA composite material crack monitoring and repair theory.

Thermal stresses in bimetallic plate under induction heating by nonstationary electromagnetic field

A thermomechanical problem is formulated for a bimetallic plate subjected to induction heating by a nonstationary electromagnetic field. As the object of the study, a plate with layers made of stainless steel and copper is selected. The stress intensities in the constituent layers of the plate are numerically analyzed on its external surfaces and at the contact interface of the constituent layers. The analysis is conducted based on the amplitude-frequency characteristics and the duration of the nonstationary electromagnetic action. The research is carried out for two cases of electromagnetic carrier wave frequencies including those equal to the first resonance frequency and those extending outside the resonance frequency range of the electromagnetic field.

Joint formation mechanism and mechanical properties of laser brazed Zn coated steel under different defocusing conditions

Laser brazing, producing a class-A joint surface in automotive, relies on the defocus control to manage laser heating mode and braze performance. This work demonstrates that the laser interaction mechanism transitioned from keyhole welding to conduction brazing as defocus distances increased from −20 to ≥18 mm while keeping other parameters consistent. Uniform brazed joints were achieved at defocuses of +22, +25 and + 30 mm. Increased defocus distance resulted in a wider bead, with a larger laser irradiation area and expanded heat affected zone (HAZ), leading to increased steel melting and more Fe-rich precipitates within the Cu braze. The interfacial reaction layers remained Fe(Si) with increasing thickness as defocus changed from +22 to +30 mm, and two distinct Fe(Si) phases were initially identified. The steel Zn coating evaporated upon direct laser irradiation at upper two regions while participated in interfacial reactions at the weld root. At the weld root, a dramatic phase transition from Zn–Cu to Cu was observed, with liquid Zn(Cu) phases particularly forming in joints with a +30 mm defocus, led to solidification cracks that acted as failure initiation sites during tensile testing. Cracks propagated along the interfacial reaction layer/bead interface, or along large Fe-rich precipitates within the bead. A +30 mm defocus produced a lower hardness HAZ than with a +22 mm defocus, due to the higher content of bainite and tempered martensite resulting from a slower cooling rate. This work provides insights into optimizing laser brazing parameters for Zn-coated steel.

Polyoxometalate Reinforced Perovskite Phase for High-Performance Perovskite Photovoltaics.

Ionic hybrid perovskites face challenges in maintaining their structural stability against non-equilibrium phase degradation, therefore, it is essential to develop effective ways to reinforce their corner-shared [PbI6]4- octahedral units. To strengthen structural stability, redox-active functional polyoxometalates (POMs) are developed and incorporated into perovskite solar cells (PSCs) to form a robust polyoxometalates/perovskite interlayer for stabilizing the perovskite phase. This approach offers several advantages: 1) promotes the formation of an interfacial connecting layer to passivate interfacial defects in addition to stabilize the [PbI6]4- units through exchanged ammonium cations in POMs with perovskites; 2) facilitates continuous structural repairing of Pb0- and I0-rich defects in the [PbI6]4- unit through redox electron shuttling of the electroactive metal ions in POMs; 3) provides guidance for selecting suitable redox mediators based on the kinetic studies of POM's effectiveness in reacting with targeted defects. The POM-reinforced device maintains 97.2% of its initial PCE after 1500 h of shelf-life test at 65°C, while also enhancing the long-term operational stability. Additionally, this approach can be generally applicable across scalable sizes and various bandgap perovskites in devices, showing the promise of using functional POMs to enhance perovskite photovoltaic performance.

Evaluation of imidazole blocking layers for perovskite stability

The prevention of AgI formation is critical for ensuring long term stability of perovskite solar cells. While sputtered metal oxide films are known for uniform dense film formation, solution phase nanoparticle coatings of metal oxides are prone to pinholes through which free iodide can migrate leading to AgI formation at the back contact. Iodide migration can be prevented through the addition of passivator or blocking layers at the perovskite/charge transport or charge transport/Ag interfaces. In this paper we evaluated a series of imidazoles as interfacial layers to prevent iodide migration from the perovskite to the Ag back contact through solution phase deposited Y:SnO2. We identified structural features of the imidazoles that contribute to an effective blocking layer. Specifically, it was found that imidazoles with conjugated planer systems and hydrogen bonding heteroatoms were able to prevent ion migration while retaining device performance. Of the materials evaluated 4-(Imidazol-1-yl)phenol had the best performance with a 60 % increase in stability verse the control under illumination at short circuit conditions.

Record-Low thermal boundary resistance at bonded GaN/diamond interface by controlling ultrathin heterogeneous amorphous layer

Thermal boundary resistance (TBR) in semiconductor-on-diamond structure bottlenecks efficient heat dissipation in electronic devices. In this study, to reduce the TBR between GaN and diamond, surface-activated bonding with a hybrid SiOx-Ar ion source was initially applied to achieve an ultrathin interfacial layer. The simultaneous surface activation and slow deposition of the SiOx binder layer enabled precise control over layer thickness (2.5–5.3 nm) and formation of an amorphous heterogeneous nanostructure comprising a SiOx region between two inter-diffusion regions. Crucially, the 2.5-nm-thick interfacial layer achieved a TBR of 8.3 m2⋅K/GW, a record low for direct-bonded GaN/diamond interface. A remarkable feature is that the TBR is extremely sensitive to the interfacial thickness; Varying from 8.3 m2⋅K/GW to 34 m2⋅K/GW with thickness difference of only 2.8 nm. Theoretical analysis revealed the origin of this phenomena: a diamond/SiOx inter-diffusion layer extend the vibrational frequency, far exceeding that of crystalline diamond, which increases the lattice vibrational mismatch and suppresses phonon transmission.

Electron trapping in HfO2 layer deposited over a HF last treated silicon substrate

Electron trapping in HfO2-based MOS structures was studied through pulsed capacitance-voltage (C-V) technique. 10 nm HfO2 layer was deposited by atomic layer deposition over a HF last treated Si substrate. The C-V curves were observed to shift to positive voltages driven by the positive applied voltage along the pulses, consistent with electron trapping due to tunneling transitions between the substrate and pre-existing defects within the oxide and the subsequent lattice relaxation through electron-phonon interaction. The dependences of the voltage shift for a given capacitance value (ΔVC) with stress bias and time, allowed to distinguish two mechanisms. An initial trapping process occurs for times shorter than the microsecond, probably associated with a thin non-stoichiometric SiOx interfacial layer, which is followed by a trapping process that starts after tens of μs and progressively slowed down, associated with traps within the HfO2 layer. Numerical simulations yield for the HfO2 traps an energy of 1.3 eV below the conduction band edge, decreasing exponentially with the distance from the Si interface with a characteristic length of 1.7 nm; and phonon and relaxation energies of 50 meV and 1 eV, respectively. These physical parameters are consistent with previous reports of electron trapping in HfO2 layers deposited on a controlled interfacial layer, suggesting that trapping properties of defects inside the HfO2 layer are insensitive to the treatment of the Si surface before HfO2 deposition. On the other hand, the observed large initial trapping suggests that the non-controlled SiOx interfacial region is more defective than a controlled one.

Reactivity tuning of metastable intermolecular composite Al/PFOA by polydopamine interfacial control

Controlling the high reactivity resulting from interfacial contact between nanoscale components poses a significant challenge. This study introduces an approach utilizing an aluminum (Al) surface-modified material to regulate the interaction between Al and perfluorooctanoic acid (PFOA), employing an in-situ synthesized polydopamine (PDA) interfacial layer. The optimal ratio was determined through molecular dynamics simulations. Various characterization techniques, including scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), transmission electron microscopy (TEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS), were employed to comprehensively analyze the structure and elemental distribution of the samples. The findings indicate that the PDA coating process did not alter the surface structure of Al while maintaining the integrity of the functional groups of both PDA and PFOA. Results from simultaneous thermal analysis (TG-DSC) demonstrate that the PDA interfacial layer increased the pre-ignition reaction (PIR) peak temperature of PFOA/Al by 2 °C and enhanced the heat release of the PIR and fluorination reaction by 1.3 and 34.8 times, respectively. Thermal analysis kinetics investigation revealed a reduction of 6.66 kJ⋅mol−1 in the activation energy of the fluorination reaction and an increase of 20.28 kJ⋅mol−1 in the activation energy of the PIR. Furthermore, the combustion heat and reaction degree of PFOA/Al@PDA powder increased by 43.4 % and approximately 8 %, respectively, compared to PFOA/Al powder generated by physical mixing. This study demonstrated that the inclusion of PDA modifiers in the PFOA/Al system effectively controls the exothermic reaction between fuel and oxidant and enhances the oxidation degree of Al.

Microstructure and properties of C18150 Cu/8011 Al/C18150 Cu laminated composites

In order to solve the problem of insufficient strength and electrical conductivity of Cu–Al composites, C18150 Cu/8011 Al/C18150 Cu composites with a thickness of 1.6 mm were fabricated by cast rolling method in this paper, followed by cold rolling and annealing. The interfacial microstructure and precipitation behavior were analyzed through electron backscatter diffraction, scanning electron microscopy, and transmission electron microscopy in detail. The research results show that the three-layer interfaces from the Al layer to the Cu layer are Al2Cu, AlCu, and Al4Cu9, respectively. The interface of the Al layer and Al2Cu layer demonstrate a coherent matching relation, the interface of the Al2Cu layer and AlCu layer shows a semi-coherent matching relation, and the interfaces between AlCu and Al4Cu9, and Al4Cu9 and Cu, are incoherent matching relation. In addition, the Al2Fe3Si4 and Cr precipitations were formed in the composites. The composites exhibit extremely outstanding strength-plasticity-conductivity, and the tensile strength and elongation are 295 MPa and 21%, respectively. The electrical conductivity of the Cu and Al layers is 90.6% and 47.6% according to the International Copper Standard, respectively. This study is useful in guiding the further development and application of high-strength and high-conductivity Cu/Al laminated composites.

In‐Situ Constructing a Mixed‐Conductive Interfacial Protective Layer for Ultra‐Stable Lithium Metal Anodes

Lithium metal batteries are the most promising next‐generation energy storage technologies due to their high energy density. However, their practical application is impeded by serious interfacial side reactions and uncontrolled dendrite growth of lithium metal anode. Herein, copper 2,4,5‐trifluorophenylacetate is designed and explored to stabilize lithium metal anode by in‐situ constructing a dense and mixed‐conductive interfacial protective layer. The formed passivated layer not only significantly inhibits interfacial side reactions by avoiding direct contact between lithium metal anode and electrolyte but also effectively suppresses lithium dendrite growth due to the unique inorganic‐rich compositions and mixed‐conductive properties. As a result, the copper 2,4,5‐trifluorophenylacetate‐treated lithium metal anodes show greatly improved cycle stability under both high current density and high areal deposition capacity. Notably, the assembled liquid symmetrical cells with copper 2,4,5‐trifluorophenylacetate‐treated lithium metal anodes can stably work for more than 3000, 5000, and 4800 h at 1.0 mA cm−2–1.0 mAh cm−2, 2.0 mA cm−2–5.0 mAh cm−2, and 10 mA cm−2–5.0 mAh cm−2, respectively. Furthermore, the assembled liquid full cell with a high LiFePO4 loading (~16.9 mg cm−2) shows a significantly enhanced cycle life of 250 cycles with stable Coulombic efficiencies (>99.1%). Moreover, the assembled all‐solid‐state lithium metal battery with a high LiNi0.6Co0.2Mn0.2O2 loading (~5.0 mg cm−2) also exhibits improved cycle stability. These findings underline that the copper 2,4,5‐trifluorophenylacetate‐treated lithium metal anodes show great promise for high‐performance lithium metal batteries.

Decylammonium sulfate post-treatment for efficient hole-conductor-free printable perovskite solar cells with reduced voltage loss

Hole-conductor-free printable mesoscopic perovskite solar cells (p-MPSCs) have attracted widespread attention for their low cost, up-scalability, and exceptional stability. However, the high defect density of perovskite and the absence of interfacial barrier layer between perovskite and carbon electrode cause profound open-circuit voltage (VOC) loss, which results in uncompetitive power conversion efficiency (PCE). Herein, an anion-cation synergy of decylammonium sulfate (DA2SO4) is utilized for suppressing VOC loss of p-MPSCs via a facile post-treatment method. DA+ cations transform the perovskite adjacent to carbon electrode into wide-bandgap 2D perovskite for blocking electrons, while the SO42− anions interact with undercoordinated lead centers for reducing defect density. As a result, the modified device delivers an enhanced PCE from 17.78% to 19.59%, with an improved VOC from 0.98 V to 1.06 V. Meanwhile, the modified device without any encapsulation exhibits excellent moisture stability with the PCE remained almost 99% of the initial value after 528 h aging in 75% RH air at room temperature.

OG-POSS synergistically enhances the corrosion resistance and adhesion property of primer for silicone resin thermal protective coating

Octaglycidyldimethylsilyl polyhydric silsesquioxane (OG-POSS) in coordination with tetraethyl orthosilicate, tetrapropyl orthosilicate and tetrabutyl orthosilicate mixed solution was applied to the bonding of metal substrate and silicone resin thermal protective coating. The influence of OG-POSS addition on the interface of primer was systematically investigated by means of scanning electron microscope (SEM), salt spray test, thermogravimetric infrared spectroscopy (TGA-IR) and back temperature test. Results showed that the addition of OG-POSS favored the formation of a silane film of the primer, resulting in a more compact and continuous film. At the same time, the silane film had excellent corrosion resistance and adhesion, with a maximum adhesion strength of about 1.42 MPa. In addition, OG-POSS provided a unique Si-O-Si cage structure in the primer, which improved the ablation resistance of the interface layer, preventing the degradation and peeling of the coating in harsh environments.

Glycolic acid doped PFN-Br as cathode interface to achieve high-efficiency in organic solar cells

Small compounds are often utilized to adjust the cathode interface of organic solar cells (OSCs) due to their low batch change, easy synthesis, unambiguous chemical structure, and low cost. In this work, the alcohol-soluble small molecule material Glycolic acid was doped into the electron transport material Poly(9, 9-bis(3′-(N, N-dimethyl)-N-ethylammoniumpropyl-2, 7-fluorene)-alt-2, 7-(9, 9-dioctylfluorene)) dibromide (PFN-Br) to modify the performance of the cathode interface layer (CIL). The CIL doped with Glycolic acid has better surface morphology, which is conducive to charge transport and extraction. In addition, the introduction of Glycolic acid improves the hydrophilicity of CIL, makes the metal electrode have good contact with CIL, and helps to improve the stability of the OSCs. Additionally, it suppresses the device's trap-assisted recombination and bimolecular recombination, hastening exciton dissociation and charge collection. As a result, the power conversion efficiency (PCE) of OSCs based on PM6: Y6 blend film has risen from 15.26 % to 15.91 %. After 312 hours of stability testing, the aforementioned doped devices still have device performance higher than standard device. Furthermore, based on PBDB-T: IT-M mix film, the PCE of the doped device and reference device was 11.29 % and 10.55 %, respectively. This study suggests that using the alcohol-soluble small-molecule material Glycolic acid can increase the organic solar cells' (OSCs') efficiency. This study provides a new method for manufacturing high-performance OSCs.