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Efficient removal of pollutant formaldehyde (HCHO) at room temperature using transition-metal oxides remains a huge challenge to date. Manganese oxide can oxidize formaldehyde, however, how to control the valence states of manganese is the key to further improve the removal efficiency. We have successfully prepared porous manganese oxide nanowires (MnOx NWs) with large surface area and multiple valence states of manganese using simple electrospinning followed by thermal calcination and potassium permanganate solution post-treatment (C/S process). The contents of trivalent and tetravalent manganese increased significantly after C/S process. Moreover, the composition of silver oxide coated silver nanowires (Ag@Ag2O NWs) is realized by assistance with oxygen plasma, which further enhanced high valence manganese. The formaldehyde removal efficiency by Ag@Ag2O–MnOx composite nanowires can reach 93.7%. The high-efficient catalytic activity is confirmed to attribute to the higher surface area of composite nanowires, the high-valence manganese and the silver oxide for oxidation of formaldehyde.

Owing to the rapid development of wireless communication technologies, microwave dielectric ceramics have been proposed to facilitate an increase in the performance of functional ceramic components. Herein, CaTiO3-LnAlO3(Ln=La, Nd) ceramics were synthesized via reaction sintering to produce low-cost, high-efficiency, materials. The reaction-sintering method, which imparts excellent comprehensive properties, was used to fabricate these ceramics. The subtle variations in the densification behavior, phase transformation, phase composition, microstructural evolution, and performance exhibited by the CaTiO3-LnAlO3(Ln=La, Nd) ceramics were systematically evaluated. The X-ray diffraction patterns obtained from each sample indicate that the Ca0.61La0.39Al0.39Ti0.61O3 (CTLA) and Ca0.7Nd0.3Ti0.7Al0.3O3 (CTNA) phases were generated under certain environmental conditions. The as-synthesized ceramics exhibited excellent performance parameters: er = 39.1, Q × f = 45 635 GHz, τf = −1.48 ppm/°C and er = 44.03, Q × f = 46 269 GHz, τf = +2.63 ppm/°C, respectively. In addition, the ceramics retained their strong performance parameters irrespective of external temperature fluctuations. The reaction sintering method provides an economical, convenient, and facile method for the fabrication of CaTiO3-LnAlO3(Ln=La, Nd) ceramics which, in turn, imparts broad prospects for the application and development of these materials.

To expand the future clinic applications of biodegradable magnesium alloy, polymer coatings with excellent biocompatibility are the keys to solve the local alkalinity and rapid hydrogen release. Natural−organic silk fibroin provides an approach to fabricate a protective coating on biomedical Mg−Zn−Ca alloy, however, the adhesion force and mechanical properties of the coating on substrates are ought to be further improved without any chemical conversion/intermediate layer. Hereby, based on VUV/O3 surface activation, a hybrid of silk fibroin and sodium alginate is proposed to enhance the adhesion force and mechanical properties of the composite coatings on hydrophilic Mg−Zn−Ca alloy surfaces. Various mass ratios of sodium alginate addition were investigated to achieve the optimum coating strategy. The nanoscratch test and nanoindentation test confirmed that the adhesion force was tripled and mechanical properties index was significantly improved when the mass ratio of silk fibroin/sodium alginate was 70/30 compared to pure silk fibroin or sodium alginate coatings. Meanwhile, the corrosion rate of the coated Mg−Zn−Ca alloy was significantly delayed with the addition of sodium alginate, resulting in a reaction layer during corrosion process. Furthermore, the mechanisms for both adhesion and corrosion processes were discussed in detail. Our findings offer more possibilities for the controllable surface performance of degradable metals.

Cu/SiO2 hybrid bonding with planarized dielectric and isolated metal connections can realize ultradense interconnects (e.g., ≤1 μm) by eliminating the microbumps and underfill through the direct bonding of Cu-Cu and SiO2-SiO2. However, the low-temperature bonding of Cu-Cu (oxide-free surface) and SiO2-SiO2 (hydroxylated surface) is difficult to be compatible in a mechanism. We circumvent this contradiction by constructing a co-hydroxylated functional surface on a Cu/SiO2 hybrid platform. By combining and optimizing the protocol of Ar/O2 plasma activation and formic acid solution immersion, an -OH active layer was successfully established on the Cu and SiO2 surfaces simultaneously, and the increased total surface area provided more adsorption sites for hydroxyl groups. A Cu-Cu interface with sufficient atom diffusion, substantial grain growth, and fewer microvoids was obtained at 200 °C. Notably, the carbon-related interlayer that may degrade the interfacial performance could be effectively inhibited across the optimized SiO2-SiO2 interface even if organic acid was introduced in the protocol. This low-temperature Cu/SiO2 hybrid bonding via a co-hydroxylated strategy may inspire the development of a memory-centric chip architecture and functional integrated circuits delivering a monolithic-like performance in the future hyperscaling era.

In the present work, a high quality (Q) Ca1.15Sm0.85Al0.85Ti0.15O4 (CSAT) ceramic was prepared via reaction sintering (RS) method. The phase structure, surface morphology, packing fraction (PF), and valence bond of the ceramic were systematically investigated. By studying the X-ray diffraction (XRD) pattern of the ceramic, it was determined to exhibit a single-phase tetragonal structure with the dimensions of a = b = 3.6943(13)A and c = 12.0320(23)A and volume of V = 164.22(10) A3. The influence of the intrinsic quality loss factor on the Q × f value was investigated by calculating the PF. Simultaneously, the bond valence of the samarium (Sm) sites was evaluated to elucidate the relationship with the temperature coefficient of resonant frequency (τf). The CSAT ceramic was sintered at 1550 °C for 6 h and exhibited exceptional characteristics in terms of the relative dielectric constant (er) = 17.5, quality factor (Q × f) = 66700 GHz, and τf = −6.93 ppm/°C. These results highlighted the excellent suitability of the RS method for preparing CSAT ceramics with outstanding microwave dielectric properties.

0.85(0.74CaTiO3–0.26SmAlO3)–0.15Ca1.15Sm0.85Al0.85Ti0.15O4 (CSC) composite ceramics were prepared by a reaction-sintering method. The phase structure, sintering behavior and microwave dielectric properties of CSC ceramics were investigated. The preparation process of reaction-sintering route (RS) is simple. XRD patterns show that Ca0.74Ti0.74Sm0.26Al0.26O3 (similar to CaTiO3), SmAlO3 and Ca1.15Sm0.85Al0.85Ti0.15O4 phases are formed in the CSC ceramics. The grain size and dielectric constant of CSC ceramics increase with rising the sintering temperature. As the sintering temperature increases, the quality factor (Q × f) and τf value of the CSC ceramics increase to the maximum values first and then decrease. The bulk density fluctuates up and down around a value, but little change. The ceramics sintered at 1500 °C got the best microwave dielectric performances with er = 35.9, Q × f = 49,221 GHz, τf = − 0.53 ppm/°C.

A novel La2MgGeO6 ceramic was synthesized through a solid-state reaction process within a sintering temperature range of 1450–1550 °C. By a combination of X-ray diffraction and Rietveld refinement analyses, the ceramics were found to have a pure hexagonal phase structure belonging to space group R3/146. The scanning electron microscopy images revealed that the ceramic grains were closely connected. The effects of internal (lattice energy, valence bond, and fraction packing) and external factors (density) on the microwave properties of ceramics were also studied. The ceramic exhibited excellent microwave dielectric performances, with a relative permittivity (Ɛr) of 21.2, a quality factor (Q × f) of 52 360 GHz, and a temperature coefficient of resonant frequency (τf) of −44.2 ppm/°C, when sintered at 1500 °C for 4 h. The τf value of the La2MgGeO6 ceramic doped with CaTiO3 could be adjusted to zero. Particularly, 0.2La2MgGeO6-0.8CaTiO3 ceramics have good microwave dielectric properties with τf = +2.1 ppm/°C, Q × f = 15 610 GHz, and Ɛr = 40.3.

Novel 0.695CaTiO3-0.305SmAlO3+xwt% CeO2 (x = 0, 0.5, 1.0, 1.5) ceramics were fabricated using a reaction-sintering (RS) approach. The crystal structure, morphology, and microwave dielectric properties of ceramics were systematically studied. The addition of CeO2 could effectively improve the sintering behavior of 0.695CaTiO3-0.305SmAlO3 (CTSA) ceramics. When x = 0.5 wt%, the ceramics exhibited optimal microwave dielectric properties, with er = 43.9, Q×f = 48 779 GHz, and τƒ = −0.24 ppm/°C, thereby indicating that the samples prepared via the RS route possess superior dielectric properties compared to those prepared by the conventional solid phase reaction. The results demonstrate that CaTiO3-SmAlO3 ceramics can be prepared simply and efficiently through a reaction-sintering process.

NaTaO3 ferroelectric ceramics sintered at 1550 °C exhibit high relative permittivity and outstanding microwave dielectric properties of er = 113.76, Q × f = 8824 GHz, and τƒ = +645 ppm/°C in the low-frequency band (3.5195 GHz). The high relative permittivity is advantageous for the miniaturization of modern wireless communication devices. A near zero temperature coefficient of the resonance frequency (τƒ = +1.05 ppm/°C) and good microwave dielectric properties (Q × f = 54,680 GHz, er = 19.42) were obtained for 0.92MgTiO3-0.08NaTaO3 ceramics. Moreover, the sintering temperature of MgTiO3 could be decreased from 1350 °C to 1200 °C. Hence, NaTaO3 is a high-potential microwave dielectric material for adjusting systems with a negative temperature coefficient of resonance frequency.

We propose a plasma-activated direct bonding process at low temperatures (≤200 °C) to form heterostructures between single-crystalline SiC and conventional Si-based substrates (SiO2, Si, and glass) without any interlayers. Surface activation was performed via an inductively coupled O2 plasma for 60 s with a lower bombardment damage position. The SiC surfaces were much more hydrophilic after activation, and the generation of defect states was suppressed. Consequently, void-free and robust bonding interfaces of SiC/SiO2, SiC/Si and SiC/glass were successfully achieved. There were no carbon-enriched layers across the bonding interfaces, which could improve the electrical properties of SiC-based devices. Additionally, the bonding interface of SiC/glass exhibited excellent optical transparency, and interfacial corrosion resistance was confirmed via immersion tests in biological solutions. This bonding method provides a feasible route towards industry-compatible heterogeneous integration of single-crystalline bulk SiC onto Si-based platforms for electronic, optical, mechanical, and biomedical applications.

Using the solid-state reaction method, novel series of 3CaO–RE2O3–2WO3 (RE = La, Nd and Sm) dielectric ceramics materials were fabricated, and the crystal structure and microstructure were studied through X-ray diffraction (XRD) and scanning electron microscope (SEM), respectively. The Ca3La2W2O12 (CLW) ceramic exhibited a single pure phase with a rhombohedral structure, and Ca3Nd2W2O12 (CNW) and Ca3Sm2W2O12 (CSW) ceramics had similar crystal structures with CLW. 3CaO–RE2O3–2WO3 (RE = La, Nd and Sm) ceramics are packed tightly, and the grains exhibited clear boundaries and uniform size. The CLW, CNW, and CSW ceramics sintered at 1375 °C for 4 h possessed excellent microwave dielectric properties: Ɛr = 19.1, Q × f = 34370 GHz, τf = − 80 ppm/°C; Ɛr = 19.3, Q × f = 36610 GHz, τf = − 74 ppm/°C and Ɛr = 18.8, Q × f = 23240 GHz, and τf = − 68 ppm/°C, respectively. Moreover, the (1 − x)CNW–xTiO2 (0.3 ≤ x ≤ 0.6) and (1 − y)CNW–yCaTiO3 (0.4 ≤ y ≤ 0.7) ceramics were designed and prepared to get a thermally stable material. The addition of TiO2 and CaTiO3 had a significant impact on the performances of ceramics. With increasing the TiO2 and CaTiO3 content, the relative permittivity (Ɛr) and temperature coefficient of resonance frequency (τf) values of ceramics increased, but the quality factor (Q × f) values of ceramics decreased. Especially, 0.55CNW–0.45TiO2 and 0.45CNW–0.55CaTiO3 ceramics sintered at 1375 °C for 4 h had microwave dielectric properties of Ɛr = 22.4, Q × f = 32,490 GHz, and τf = − 0.5 ppm/°C and Ɛr = 23.4, Q × f = 6440 GHz, and τf = − 1.5 ppm/°C, respectively.

Pressureless and low-temperature sintering of Ag paste has been mentioned as a promising strategy to solve the poor performance of large-area chips. In this paper, we develop a two-step surface activation process to achieve rapid pressureless and low-temperature bonding of Cu in air using a micron-scale Ag paste for large-area chips. The organics that adsorb on the Ag particles are initially removed by oxygen plasma cleaning, and the silver oxide byproducts are subsequently deoxidized by a methanol/hydroxide mixed vapor treatment. The two-step activation significantly improves the sinterability of the micron-scale Ag paste, leading to excellent interfacial properties after rapid sintering at 200 °C for only 10 min in air. Robust-bonded joints are achieved with a shear strength and thermal conductivity that are four times higher than those of the non-activated bonded joints. The bonding strength and thermal conductivity of the Cu joint structure are approximately 25 MPa and 96 W/mK, respectively, which are superior to those of traditional Sn–Pb solders. Void-free bonding interfaces are confirmed by large-area chips even without pressure in air; this method shows great potential for the cost-effective commercial packaging of power electronics.

Compared with continuous node scaling in a two-dimensional (2D) plane, advanced three-dimensional (3D) integration finds a new pathway to expand Moore's Law in the vertical direction. The essence of advanced 3D integration technology relies on the dense vertical interconnection, and state-of-the-art metal/oxide hybrid bonding provides such an ideal fine-pitch structure (≤ 1 µm) by eliminating microbump and underfill. Of the various hybrid bonding platform, Cu/SiO 2 hybrid bonding structure is the most promising candidate due to the excellent electrical and mechanical properties of Cu and SiO 2 , respectively. However, the feasible Cu/SiO 2 hybrid bonding technology often requires high temperature (-400°C) currently, which is not desirable for temperature-sensitive chips. Here, we develop a novel two-step cooperative surface activation method to overcome this bottleneck. Based on the combination of plasma activation and acid treatment of this cooperative surface activation, the atomic smooth Cu and SiO 2 surface with hydrophilic layers were obtained, and the strong homogeneous bonding of Cu-Cu and SiO 2 -SiO 2 was realized at 200°C. Eventually, the Cu/SiO 2 hybrid bonding device was successfully achieved, which void-free and atomically interconnected Cu-Cu, SiO 2 -SiO 2 , and even Cu-SiO 2 interfaces were obtained simultaneously. This hybrid bonding structure realized by cooperative surface activation brings unprecedented 3D integration feasibility and flexibility.

In this study, plasma activation is demonstrated as a surface activation method in SiCOI (SiC-on-insulator) substrate fabrication, silicon-based wafer bonding, and pressure-less Ag nanopaste sintering for 3D integration. Oxygen inductive coupled plasma (ICP) shows high efficiency in organic removal and surface activation, which not only achieves a tight and reliable direct bonding but also serves for pressure-less sintering of Ag nanopaste by pre-decomposing the organic components. The oxygen plasma activation has exerted its multi-functional nature and excellent performance in both direct and indirect bonding methods. We believe that the plasma activation has sufficient potential as a versatile and efficient approach for heterogeneous integration and high-density packaging.

Silicon carbide is well known as a compelling third-generation semiconductor material. SiC-on-insulator substrate performs superior electronic isolation and operates as a high-speed and high-power platform. In contrast to existing manufacturing methods, there is an urgent need for a low temperature process with lower interfacial stress and high quality. Wafer direct bonding has been developed for many years because this technology enables composite structures regardless of material. However, the bonded sample should anneal to further improve the strength. The interfacial stress caused by high temperature is still unsolved. Plasma activated bonding is known as a method that requires a lower annealing process. Here, we adopt O 2 plasma activation as a pre-treatment and bond hydrophilic surfaces at room temperature. Furthermore, we designed a step annealing curve to reduce the maximum temperature to 200 °C while ensuring bonding strength. A uniform and defect-free bonding interface can be observed by transmission electron microscopy. This technique is suitable for fabricating high quality SiC-on-insulator platforms for optoelectronic devices.

Based on a two-step plasma surface activation process (O2 followed by N2 plasma), silk fibroin coating was prepared on Mg-Zn-Ca alloy without conversion layer to retard the corrosion. This method achieved homogenized surfaces with better hydrophilicity and increased functional groups, significantly improving the adhesion force. The corrosion resistance of coated magnesium alloy was significantly enhanced compared to that of bare samples. Nanoscratch combined with corrosion behavior indicated that the remarkably improvement of anticorrosion ability attributed to the protective layer and the increased adhesion force. Our findings provided more possibilities for corrosion protection of degradable metals.

Direct bonding at low temperature is an attractive technology for joining dissimilar materials without large thermal stress. Vacuum ultraviolet (VUV) activation is an effective way for surface cleaning with less damage. Meanwhile, the obtained hydrophilic surfaces are also beneficial for the direct bonding. In this paper, we developed a VUV/O3 activated bonder for the direct bonding of Si-based materials at low temperature. High bonding strength for Si/glass and glass/glass bonded pairs was achieved after annealing at 200 oC. Atomic force microscopy (AFM) and water contact angle tester were conducted to analyze effects of VUV on surface roughness and wettability. Si-Si, Si-glass and glass-glass bonding interfaces were also observed by transmission electron microscopy (TEM). Defect-free and tight interfaces of Si/Si and Si/glass were obtained. However, the glass/glass bonding interface was full of microvoids which can be attributed to the less deformation of subsurfaces during the annealing process. Moreover, based on the surface and interface studies, bonding mechanisms for Si-based materials direct bonding via VUV activation was discussed.

A controllable plasma-activated method to achieve pressureless sintering of Ag nanoparticles is proposed for low-temperature bonding. O2 plasma activation is employed to effectively decompose organics coated on the nanoparticles prior to sintering, avoiding the loose interfacial microstructures. Therefore, robust bonding Cu-Cu joints with high shear strength (>20 MPa) can be formed at a low temperature of 200 °C without requiring additional pressure. This rapid and controllable activation method significantly enhances the sinterability of the Ag particles, leading to a dense microstructure. The improved thermal conductivity is three times higher than the one prepared without plasma activation.

High-precision aligned wafer bonding is essential to heterogeneous integration, with the device dimension reduced continuously. To get the alignment more accurately and conveniently, we propose a moir&eacute, based alignment method using centrosymmetric grating marks. This method enables both coarse and fine alignment steps without requiring additional conventional cross-and-box alignment marks. Combined with an aligned wafer bonding system, alignment accuracy better than 300 nm (3&sigma, ) was achieved after bonding. Furthermore, the working principle of the moir&eacute, based alignment for the backside alignment system was proposed to overcome the difficulty in bonding of opaque wafers. We believe this higher alignment accuracy is feasible to satisfy more demanding requirements in wafer-level stacking technologies.