Rapid heating induced ultrahigh stability of nanograined copper

Regulating Strain and Electronic Structure of Indium Tin Oxide Supported IrOx Electrocatalysts for Highly Efficient Oxygen Evolution Reaction in Acid

The development of proton exchange membrane water electrolysis is a promising technology for hydrogen production, which has always been restricted by the slow kinetics of the oxygen evolution reaction (OER). Although IrOx is one of the benchmark acidic OER electrocatalysts, there are still challenges in designing highly active and stable Ir-based electrocatalysts for commercial application. Herein, a Ru-doped IrOx electrocatalyst with abundant twin boundaries (TB-Ru0.3Ir0.7Ox@ITO) is reported, employing indium tin oxide with high conductivity as the support material. Combing the TB-Ru0.3Ir0.7Ox nanoparticles with ITO support could expose more active sites and accelerate the electron transfer. The TB-Ru0.3Ir0.7Ox@ITO exhibits a low overpotential of 203 mV to achieve 10 mA cm-2 and a high mass activity of 854.45 A g-1noble metal at 1.53 V vs RHE toward acidic OER, which exceeds most reported Ir-based OER catalysts. Moreover, improved long-term stability could be obtained, maintaining the reaction for over 110 h at 10 mA cm-2 with negligible deactivation. DFT calculations further reveal the activity enhancement mechanism, demonstrating the synergistic effects of Ru doping and strains on the optimization of the d-band center (εd) position and the adsorption free energy of oxygen intermediates. This work provides ideas to realize the trade-off between high catalytic activity and good stability for acidic OER electrocatalysts.

Nanocrystalline copper for direct copper-to-copper bonding with improved cross-interface formation at low thermal budget

Direct copper-to-copper (Cu-Cu) bonding is a promising technology for advanced electronic packaging. Nanocrystalline (NC) Cu receives increasing attention due to its unique ability to promote grain growth across the bonding interface. However, achieving sufficient grain growth still requires a high thermal budget. This study explores how reducing grain size and controlling impurity concentration in NC Cu leads to substantial grain growth at low temperatures. The fabricated NC Cu has a uniform nanograin size of around 50 nm and a low impurity level of 300 ppm. To prevent ungrown NC and void formation caused by impurity aggregation, we propose a double-layer (DL) structure comprising a normal coarse-grained (CG) layer underneath the NC layer. The CG layer, with a grain size of 1 μm and an impurity level of 3 ppm, acts as a sink, facilitating impurity diffusion from the NC layer to the CG layer. Thanks to sufficient grain growth throughout the entire NC layer, cross-interface Cu-Cu bonding becomes possible under a low thermal budget, either at 100 °C for 60 min or at 200 °C for only 5 min.

High Stability Hypha-Like Core-Shell Nanostructure by In Situ Induced Phase Inversion for Zinc Metal Batteries

Nanomaterials are widely used in many fields for their unique physical and chemical properties and especially demonstrate irreplaceability in energy storage systems. In this paper, a novel composite of copper sulfide with hypha-like core-shell nano-structure is synthesized by in situ phase inversion method, which serves as high stability negative electrode materials of zinc-ion batteries (ZIBs). The unique structure facilitates efficient electron and ion transport, enhances the kinetics of electrochemical reactions, and effectively suppresses the undesired expansion and decomposition of transition metal compounds. As a result, the half battery exhibits high specific capacity (250.2 mAh g-1 at 0.1 A g-1), reliable rate performance, and cycle stability (98.3 mAh g-1 at 1 A g-1 after 500 cycles). Additionally, when assembled with ZnxMnO2 positive to form a full battery, it demonstrates good cycling capacity at an intermediate current density of 2 A g-1, while maintaining excellent structural stability over 5,000 cycles (61% retention).

Laser Induced Coffee-Ring Structure through Solid-Liquid Transition for Color Printing

Metallic micro/nano structures with special physicochemical properties have undergone rapid development owing to their broad applications in micromachines and microdevices. Ultrafast laser processing is generally accepted as an effective technology for functional structures manufacture, however, the controllable fabrication of specific metallic micro/nano structures remains a challenge. Here, this work proposes a novel strategy of laser induced transient solid-liquid transition to fabricate unique structures. Through modulating the transient state of metal from solid to liquid phase using the initial pulse excitation, the subsequent ultrafast pulse-induced recoil pressure can suppress the plasma emission and removal of liquid phase metals, resulting in the controllable fabrication of coffee-ring structures. The solid-liquid transition dynamics, which related with the transient reflectivity and plasma intensity, are revealed by established two temperature model coupled with molecular dynamics model. The coffee-ring structure exhibits tunable structure color owing to various optical response, which can be used for color printing with large scale and high resolution. This work provides a promising strategy for fabricating functional micro/nano structures, which can greatly broaden the potential applications.

Formation of Nanolaminated Structure with Enhanced Thermal Stability in Copper

Nanolaminated structure with an average boundary spacing of 67 nm has been fabricated in copper by high-rate shear deformation at ambient temperature. The nanolaminated structure with an increased fraction of low angle grain boundaries exhibits a high microhardness of 2.1 GPa. The structure coarsening temperature is 180 K higher than that of its equiaxial nanograined counterpart. Formation of nanolaminated structure provides an alternative way to relax grain boundaries and to stabilize nanostructured metals with medium to low stacking faults energies besides activation of partial dislocations.

Electrodeposition of (111)-oriented and nanotwin-doped nanocrystalline Cu with ultrahigh strength for 3D IC application

The mechanical performance of electroplated Cu plays a crucial role in next-generation Cu-to-Cu direct bonding for the three-dimension integrated circuit (3D IC). This work reports direct-current electroplated (111)-preferred and nanotwin-doped nanocrystalline Cu, of which strength is at the forefront performance compared with all reported electroplated Cu materials. Tension and compression tests are performed to present the ultrahigh ultimate strength of 977 MPa and 1158 MPa, respectively. The microstructure of nanoscale Cu grains with an average grain size around 61 nm greatly contributes to the ultrahigh strength as described by the grain refinement effect. A gap between the obtained yield strength and the Hall-Petch relationship indicates the presence of extra strengthening mechanisms. X-ray diffraction and transmission electron microscopy analysis identify the highly (111) oriented texture and sporadic twins with optimum thicknesses, which can effectively impede intragranular dislocation movements, thus further advance the strength. Via filling capability and high throughput are also demonstrated in the patterned wafer plating. The combination of ultrahigh tensile/compressive strength, (111) preferred texture, superfilling capability and high throughput satisfies the critical requirement of Cu interconnects plating technology towards the industrial manufacturing in advanced 3D IC packaging application.

Constrained minimal-interface structures in polycrystalline copper with extremely fine grains

Metals usually exist in the form of polycrystalline solids, which are thermodynamically unstable because of the presence of disordered grain boundaries. Grain boundaries tend to be eliminated through coarsening when heated or by transforming into metastable amorphous states when the grains are small enough. Through experiments and molecular dynamics simulations, we discovered a different type of metastable state for extremely fine-grained polycrystalline pure copper. After we reduced grain sizes to a few nanometers with straining, the grain boundaries in the polycrystals evolved into three-dimensional minimal-interface structures constrained by twin boundary networks. This polycrystalline structure that underlies what we call a Schwarz crystal is stable against grain coarsening, even when close to the equilibrium melting point. The polycrystalline samples also exhibit a strength in the vicinity of the theoretical value.