High-performance copper alloy films for barrierless metallization

In this study, we observe useful properties of V_1.1- and V_0.8N_0.4-bearing copper (Cu) films deposited on barrierless silicon (Si) substrates by a cosputtering process. The Cu_98.8(V_0.8N_0.4), or Cu(VN_x) for brevity, films exhibit low resistivity (2.9 μΩ cm) and minimal leakage current after annealing at temperatures up to 700 °C for 1 h; no detectable reaction occurs at the Cu/Si interface. These observations confirm the high thermal stability of Cu(VN_x) films. Furthermore, since these films have good adhesion features, they can be used for barrierless Cu metallization.     

NH3 Plasma Treatments of PET for Enhancing Aluminum Adhesion

A NH₃ plasma process has been studied for enhancing the adhesion of aluminum coatings on polyethyleneterephtalate (PET) films. According to our peel strength results, NH₃ plasmas increase markedly the adhesion of aluminum on PET compared to O₂ discharges, with a much shorter treatment time. A tentative model of nonhindered growth of Al-coating based on the Lewis basic character of the functionalities grafted by NH₃ plasma is proposed for Al-polymer interactions, and for explaining the various steps in the process. The effects of power input and treatment time on the polymer surface chemistry and on the metal-polymer peel strength have been evaluated. Treatment times as short as 0.1 s at 100 W proved to be the best conditions in NH₃ plasmas, for a significant increase in Al/PET adhesion, while longer treatments have a detrimental effect. This may explain why most authors have not discovered the benefits of NH₃ plasmas for improving the adhesion of metals on PET, and have preferred O₂ or air treatments. The relative basicity of PET grafted with N-containing functionalities has been measured by means of X-ray Photoelectron Spectroscopy (XPS) analysis of samples exposed to vapors of trichloromethane, a Lewis acid molecular probe. The Al/PET adhesion was evaluated by means of a 180° Peel Test.     

Metallization of a genetically engineered polypeptide

Recently, well-ordered biological materials have been exploited to pattern inorganic nanoparticles into linear arrays that are of particular interest for nanoelectronic applications. In this work, a de novo designed E. coli-expressed polypeptide (previously shown to form highly rectilinear, β-sheet-containing structures) operates as a template for divalent metal cations. EDX and TEM analysis verify the attachment of platinum ions to the histidine-rich fibril surface, which was designed specifically to facilitate attachment of chemical moieties. Following chemical reduction, TEM further confirms the formation of localized zero-valent metal aggregates with sub-nanometer interparticle spacing.     

Sequence‐Dependent dsDNA‐Templated Formation of Fluorescent Copper Nanoparticles

There are only a few systematic rules about how to selectively control the formation of DNA‐templated metal nanoparticles (NPs) by varying sequence combinations of double‐stranded DNA (dsDNA), although many attempts have been made. Herein, we develop a facile method for sequence‐dependent formation of fluorescent CuNPs by using dsDNA as templates. Compared with random sequences, AT sequences are better templates for highly fluorescent CuNPs. Other specific sequences, for example, GC sequences, do not induce the formation of CuNPs. These results shed light on directed DNA metallization in a sequence‐specific manner. Significantly, both the fluorescence intensity and the fluorescence lifetime of CuNPs can be tuned by the length or the sequence of dsDNA. In order to demonstrate the promising practicality of our findings, a sensitive and label‐free fluorescence nuclease assay is proposed.     

Pressure-induced metallization in the absence of a structural transition in the layered transition-metal dichalcogenide ZrSe2

First-principles calculations were carried out on the ZrSe₂ compound, which has been of interest owing to its technologically important physical properties. The structural, electronic and optical properties of this compound were investigated under pressure through the plane wave pseudopotential approach within the framework of density functional theory. A comparison between the computed crystal structure parameters and the corresponding experimental counterparts shows a very good agreement between them. Fitting the pressure–volume data using the third-order Birch–Murnaghan equation of state yielded a bulk modulus B₀ = 38.17 GPa and a pressure derivative of bulk modulus  = 8.2 for hexagonal ZrSe₂. The relationship between the band structure and pressure is revealed. We calculated the total density of state (TDOS) under different pressures and partial density of state (PDOS) from 0 to 10 GPa. According to our calculations, metallization of hexagonal ZrSe₂ is predicted to occur at around 10 GPa and pressure-induced band-gap engineering reveals the transformation of the indirect to direct band gap with increasing pressure. Furthermore, optical properties, such as the complex dielectric function, refractive index and reflectivity spectra of this compound, were studied for incident electromagnetic waves in an energy range up to 45 eV. The contributions to various transition peaks in the optical spectra are analyzed and discussed with the help of the energy-dependent imaginary part of the dielectric function.