Fundamental Insights into Copper-Epoxy Interfaces for High-Frequency Chip-to-Chip Interconnects.

Future processes and materials are needed to enable multichip packages with chip-to-chip (C2C) data rates of 50 GB/s or higher. This presents a fundamental challenge because of the skin effect, which exacerbates signal transmission losses at high frequencies. Our results indicate that smooth copper interconnects with relatively thin cuprous oxides (CuO, Cu) and amine-functional silane adhesion promoters improve interfacial adhesion with epoxy dielectrics by nearly an order of magnitude.

Extending Copper Interconnects and Epoxy Dielectrics to Multi-GHz Frequencies.

Future multichip packages require Die-to-Die (D2D) interconnects operating at frequencies above 10 GHz; however, the extension of copper interconnects and epoxy dielectrics presents a trade-off between performance and reliability. This paper explores insertion losses and adhesion as a function of interface roughness at frequencies up to 18 GHz. We probe epoxy surface chemistry as a function of curing time and use wet etching to modulate surface roughness.

CoCrFeNi High-Entropy Alloy as an Enhanced Hydrogen Evolution Catalyst in an Acidic Solution.

High-entropy alloys (HEAs) have intriguing material properties, but their potential as catalysts has not been widely explored. Based on a concise theoretical model, we predict that the surface of a quaternary HEA of base metals, CoCrFeNi, should go from being nearly fully oxidized except for pure Ni sites when exposed to O to being partially oxidized in an acidic solution under cathodic bias, and that such a partially oxidized surface should be more active for the electrochemical hydrogen evolution reaction (HER) in acidic solutions than all the component metals. These predictions are confirmed by electrochemical and surface science experiments: the Ni in the HEA is found to be most resistant to oxidation, and when deployed in 0.

Modifying Metastable SrBO (B = Nb, Ta, and Mo) Perovskites for Electrode Materials.

The presence of surface/deep defects in 4d- and 5d-perovskite oxide (ABO, B = Nb, Ta, Mo, etc.) nanoparticles (NPs), originating from multivalent B-site cations, contributes to suppressing their metallic properties. These defect states can be removed using a H/Ar thermal treatment, enabling the recovery of their electronic properties (i.

Deep Eutectic Solvents Mixed with Fluorinated Refrigerants for Absorption Refrigeration: A Molecular Simulation Study.

Molecular simulations were performed to evaluate mixtures of fluorinated refrigerants with deep eutectic solvents (DESs), for potential use in single-effect absorption refrigeration cycles that use low quality waste heat sources at temperatures of ∼80 °C. The refrigerants considered were the hydrofluorocarbon R245fa and the hydrofluoroolefins R1234zeE and HFO1336mzzE, whereas the DESs evaluated were 1:2 molar mixtures of choline chloride with either ethylene glycol (ethaline) or levulinic acid (levuline) as hydrogen bond donors (HBDs). Assuming the same cycle operating conditions, the waste heat cycle efficiency η was computed for all working fluid mixtures from molecular simulation results of the mixture densities and Henry's law constants of the refrigerants in the DESs, coupled with phase equilibrium calculations and the enthalpies of the pure refrigerants.

Computational Evaluation of Mixtures of Hydrofluorocarbons and Deep Eutectic Solvents for Absorption Refrigeration Systems.

We used computational tools to evaluate three working fluid mixtures for single-effect absorption refrigeration systems, where the generator (desorber) is powered by waste or solar heat. The mixtures studied here resulted from combining a widely used hydrofluorocarbon (HFC) refrigerant, R134a, with three common deep eutectic solvents (DESs) formed by mixing choline chloride (hydrogen bond acceptor, HBA) with urea, glycerol, or ethylene glycol as the hydrogen bond donor (HBD) species. The COSMOtherm/TmoleX software package was used in combination with refrigerant data from NIST/REFPROP, to perform a thermodynamic evaluation of absorption refrigeration cycles using the proposed working fluid mixtures.

Electrochemical Reduction of CO at Functionalized Au Electrodes.

Electrochemical reduction of CO provides an opportunity to store renewable energy as fuels with much greater energy densities than batteries. Product selectivity of the reduction reaction is known to be a function of the electrolyte and electrode; however, electrodes modified with functional ligands may offer new methods to control selectivity. Here, we report the electrochemical reduction of CO at functionalized Au surfaces with three thiol-tethered ligands: 2-mercaptopropionic acid, 4-pyridinylethanemercaptan, and cysteamine.

Low temperature preparation of crystalline ZrO2 coatings for improved elevated-temperature performances of Li-ion battery cathodes.

Ultrathin crystalline ZrO(2) nanofilms have been facilely deposited on LiMn(2)O(4) particles at 120 °C using atomic layer deposition. The ZrO(2) coating shows high crystallinity, conformality and homogeneity, which contribute to considerably improved electrochemical performance of LiMn(2)O(4) at elevated temperature in lithium-ion batteries.

Electrochemical and thermal grafting of alkyl grignard reagents onto (100) silicon surfaces.

Passivation of (100) silicon surfaces using alkyl Grignard reagents is explored via electrochemical and thermal grafting methods. The electrochemical behavior of silicon in methyl or ethyl Grignard reagents in tetrahydrofuran is investigated using cyclic voltammetry. Surface morphology and chemistry are investigated using atomic force microscopy, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy (XPS).