Copper Islands Research Articles

Mechanical properties of structured copper and printed silver hybrid stretchable electronic systems

Stretchable electronics can be realized using different manufacturing methods and hybrids thereof. An example of the latter is the combination of stretchable circuit boards with screen-printing, which will be discussed in this work. The hybrid stretchable electronics structures are based on photolithographically structured and rigid copper islands and screen-printed silver ink interconnections. This enables the assembly of components with a high number of contacts onto the copper islands and deformable silver ink lines between islands. The transition area between islands and lines is critical due to local stress concentration. The effect and potential mitigations were studied by measuring the electrical resistance of test interconnections under mechanical loading. The first set of samples was elongated up to 30% in tensile tests. The second set of samples was elongated 10%, 20%, and 30% in cyclic tests up to 10 000 cycles. After the tests, extensive failure analysis, e.g. scanning electron microscope, and finite element analysis were conducted. In tensile tests at maximum load, the interconnections either snap apart or their resistance increases by 640% in the transition area. Adding protective structures around the transition area, the resistance increase can be reduced to 12%. Stress concentration in the transition area can be controlled with the layout of the structures, as shown in the cyclic tests. Depending on a layout, the structures protect interconnections in the transition area (resistance <4 Ω at 10% and 20% throughout 10 000 cycles, and up to 5000 cycles at 30% elongation), or with particular designs, cause fatal damage of the circuitry and fail early. The identified failure mechanism is typically fatigue damage caused by the repeated bending of the protective structure. The observed resistance increase at the interface was closely related to the crack propagation phase in the protective structures.

A broadband intermodulation reference generator based on artificial nonlinear dipole

AbstractAccurate passive intermodulation (IM) test calls for precise IM reference for verifying and evaluating the test error from the tester, which makes the IM calibrator source with a wide working band and dynamic range important. This letter reports on a low‐cost and broadband IM generator with a compact area of 5 × 5 cm2. The broadband IM source is designed and demonstrated on the coplanar waveguide structure, where an artificial nonlinear dipole is used to generate IM reference. In special, the dipole is constructed by a diode (HSMS 2822) and two independent copper islands with optimized size. By controlling the bias voltage across the diode, the IM magnitude level can be changed accordingly. The IM tunable dynamic range is over 47.5 dB that covers GSM 800 MHz, GSM 900 MHz, DCS 1800 MHz, and TD‐LTE band. Meanwhile, the obtained IM has an improved IM‐bias flat response.

Control of the Cu morphology on Ru-passivated and Ru-doped TaN surfaces - promoting growth of 2D conducting copper for CMOS interconnects.

Prolonging the lifetime of Cu as a level 1 and level 2 interconnect metal in future nanoelectronic devices is a significant challenge as device dimensions continue to shrink and device structures become more complex. At nanoscale dimensions Cu exhibits high resistivity which prevents its functioning as a conducting wire and prefers to form non-conducting 3D islands. Given that changing from Cu to an alternative metal is challenging, we are investigating new materials that combine properties of diffusion barriers and seed liners to reduce the thickness of this layer and to promote successful electroplating of Cu to facilitate the coating of high-aspect ratio interconnect vias and to allow for optimal electrical conductance. In this study we propose new combined barrier/liner materials based on modifying the surface layer of the TaN barrier through Ru incorporation. Simulating a model Cu29 structure at 0 K and through finite temperature ab initio molecular dynamics on these surfaces allows us to demonstrate how the Ru content can control copper wetting, adhesion and thermal stability properties. Activation energies for atom migrations onto a nucleating copper island allow insight into the growth mechanism of a Cu thin-film. Using this understanding allows us to tailor the Ru content on TaN to control the final morphology of the Cu film. These Ru-modified TaN films can be deposited by atomic layer deposition, allowing for fine control over the film thickness and composition.

Optimizing the Ink Formulation for Preparation of Cu-Based Gas Diffusion Electrodes Yielding Ethylene in Electroreduction of CO2

Cu-based gas diffusion electrodes (GDE) show excellent performance in the electrochemical reduction of CO2 to ethylene. In the present work, we evaluate how the solvent of ink formulations containing Nafion-ionomer and unsupported Cu particles affects the polymerized Nafion-copper distribution in the as-prepared GDE and the obtained performance in the electrochemical reduction of CO2. Isopropanol (IPA), dimethyl sulfoxide (DMSO), ethylene glycol (EG), or N-methyl-2-pyrrolidone (NMP)) were used. Microscopic analyses of the Cu-GDEs demonstrate that NMP and DMSO lead to exposed islands of copper, with Nafion acting predominantly as an interparticle binder. Such geometry is confirmed by the relatively high electrochemical surface area (ECSA) and the low charge-transfer resistance (Rct). IPA or EG induce the formation of Cu-catalyst particles embedded into and covered by (polymerized) Nafion films, in agreement with the relatively low ECSA, and high Rct, likely due to significant polymerization and agglomeration of Nafion in the ink formulation induced by the protic solvents prior to preparation of the catalyst layer. When evaluated in the electrochemical reduction of CO2 at −1.1 V vs the reversible hydrogen electrode (RHE), the exposed particles prepared using NMP and DMSO lead to higher FE toward ethylene than EG or IPA-based GDEs (23.5% and 19.2% vs 10.2% and 13.4%, respectively). The lower ethylene FE for Nafion covered systems is tentatively attributed to the acidity and highly effective transport of protons by Nafion.

Stromatolites and calcitized evaporite in a hypersaline playa lake: Rossport Formation (Mesoproterozoic, Ontario)

ABSTRACT The Mesoproterozoic Rossport Formation of Ontario, Canada is generally interpreted as having been deposited in an intracratonic basin, most probably a rift‐related lake. While the Rossport, overall, is dominated by sandstone and shale, the Middlebrun Bay Member, in the middle of the formation, is a carbonate unit. The Middlebrun Bay Member, in exposures on the Channel Islands and along the north Shore of Lake Superior, consists most commonly of cherty, dolomitic microbial laminites and low‐relief columnar to conical forms. In contrast to typical outcrops, the Middlebrun Bay Member on Copper Island expresses as a massive, coarsely crystalline limestone unit, devoid of stromatolites or microbial laminae. Several features suggest dissolution and replacement of a primary, soluble phase such as an evaporite mineral. The top of the unit is marked by evidence of dissolution and collapse, including large sandstone clasts let down from the overlying bed. At petrographic scale, the Copper Island Carbonate comprises millimetre‐scale anhedral spar with abundant stylolites and concentration of insoluble material at grain boundaries, indicating recrystallization from a previous phase. Geochemical data from Copper Island and from correlative stromatolitic carbonate on Channel Island and mainland Ontario are consistent with hypersaline conditions, with elevated concentrations of carbonate‐associated sulphate, V and Ba. Based on these data, the massive carbonate exposed on Copper Island is interpreted as a calcitized evaporite, probably deposited originally as gypsum, and replaced by calcite during diagenesis. These data support previous work suggesting that the Middlebrun Bay interval was deposited during a period of increased aridity and low clastic influx, and further suggest that this restricted, hypersaline lake precipitated both carbonate and gypsum, comparable to modern arid playa lakes.

Whole Genome Sequencing of Methicillin-Resistant Staphylococcus epidermidis Clinical Isolates Reveals Variable Composite SCCmec ACME among Different STs in a Tertiary Care Hospital in Oman.

Staphylococcus epidermidis has been recently recognized as an emerging nosocomial pathogen. There are concerns over the increasing virulence potential of this commensal due to the capabilities of transferring mobile genetic elements to Staphylococcus aureus through staphylococcal chromosomal cassette (SCCmec) and the closely related arginine catabolic mobile element (ACME) and the copper and mercury resistance island (COMER). The potential pathogenicity of S. epidermidis, particularly from blood stream infections, has been poorly investigated. In this study, 24 S. epidermidis isolated from blood stream infections from Oman were investigated using whole genome sequence analysis. Core genome phylogenetic trees revealed one third of the isolates belong to the multidrug resistance ST-2. Genomic analysis unraveled a common occurrence of SCCmec type IV and ACME element predominantly type I arranged in a composite island. The genetic composition of ACME was highly variable among isolates of same or different STs. The COMER-like island was absent in all of our isolates. Reduced copper susceptibility was observed among isolates of ST-2 and ACME type I, followed by ACME type V. In conclusion, in this work, we identify a prevalent occurrence of highly variable ACME elements in different hospital STs of S. epidermidis in Oman, thus strongly suggesting the hypothesis that ACME types evolved from closely related STs.

Black Phosphorus n-Type Doping by Cu: A Microscopic Surface Investigation

We study surface charge transfer doping of exfoliated black phosphorus (bP) flakes by copper using scanning tunneling microscopy (STM) and spectroscopy (STS) at room temperature. The tunneling spectra reveal a gap in correspondence of Cu islands, which is attributed to Coulomb blockade phenomena. Moreover, using line spectroscopic measurements across small copper islands, we exploit the potential of the local investigation, showing that the n-type doping effect of copper on bP is short-ranged. These experimental results are substantiated by first-principles simulations, which quantify the role of cluster size for an effective n-type doping of bP and explain the Coulomb blockade by an electronic decoupling of the topmost bP layer from the underlying layers driven by the copper cluster. Our results provide novel understanding, difficult to retrieve by transport measurements, of the doping of bP by copper, which appears promising for the implementation of ultra-sharp p-n junctions in bP.

A New Model for the Coldwell Complex and Associated Dykes of the Midcontinent Rift, Canada

AbstractMafic intrusions on the NE shoulder of the Midcontinent Rift (Keweenawan LIP), including Cu–PGE mineralized gabbros within the Coldwell Complex (CC), and rift parallel or radial dykes outside the CC are correlated based on characteristic trace element patterns. In the Coldwell Complex, mafic rocks are subdivided into four groups: (1) early metabasalt; (2) Marathon Series; (3) Layered Series; (4) Geordie–Wolfcamp Series. The Marathon Series are correlated with the rift radial Abitibi dykes (1140 Ma), and the Geordie–Wolfcamp Series with the rift parallel Pukaskwa and Copper Island dykes. U–Pb ages determined for five gabbros from the Layered and Marathon Series are between 1107·7 and 1106·0 Ma. Radiogenic isotope ratios show near chondritic (CHUR) εNd(1106 Ma) and 87Sr/86Sri values that range from –0·38 to +1·13 and 0·702537 to 0·703944, respectively. Distinctive geochemical properties of the Marathon Series and Abitibi dykes, such as Ba/La (14–37), Th/Nb (0·06–0·12), La/Sm (3·8–7·7), Sr/Nd (21–96) and Zr/Sm (9–19), are very different from those of the Geordie–Wolfcamp Series and a subset of Copper Island and Pukaskwa dykes with Ba/La (8·7–11), Th/Nb (0·12–0·13), La/Sm (6·7–7·9), Sr/Nd (5–7·8) and Zr/Sm (18–24). Each unit exhibits covariation between incompatible element ratios such as Zr/Sm and Nb/La or Gd/Yb, Sr/Nd and Ba/La, and Nb/Y and Zr/Y, which are consistent with mixing relationship between two or more mantle domains. These characteristics are unlike those of intrusions on the NW shoulder of the MCR, but resemble those of mafic rocks occurring in the East Kenya Rift. The results imply that an unusual and long-lived mantle source was present in the NE MCR for at least 34 Myr (spanning the 1140 Ma Abitibi dykes and the 1106 Ma Marathon series) and indicate potential for Cu–PGE mineralization in an area much larger than was previously recognized.

A Decrease in the Exchange Bias Caused by an Increase in the Effective Thickness of the Copper Layer in the NiFe/Cu/IrMn Heterostructures

In a series of NiFe/Cu/IrMn structures with a variable effective thickness of the nonmagnetic copper interlayer (up to its absence in the NiFe/IrMn sample), we observed a decrease in the exchange bias and coercive force with an increase in the effective thickness of the copper layer. The coalescence of copper islands when the effective thickness of the copper layer reaches 1 nm changes the contact exchange interaction between the ferromagnet and antiferromagnet in NiFe–IrMn to indirect exchange interaction through the conduction electrons of the copper layer in NiFe–Cu–IrMn. The structural quality of single-crystal ferromagnetic and antiferromagnetic layers does not change, and the magnetization reversal occurs without the participation of domains in the temperature range of 2–300 K. Simulation of the deposition dynamics demonstrates the island structure of the film at the initial stages up to an effective thickness of 1 nm.

Stitching equipotential metallization areas on the double-sided printed circuit board

The linking (stitching) of equipotential metallization areas located on different layers of the printed circuit board is carried out using layer-to-layer vias. The purposes can be different, e. g.: heat removal from heat-loaded components, reduction of the thermal resistance of the board (reducing the risk of warping the board when exposed to thermal loads); reduction of the return current loop of high-speed signals, including differential ones; reduction of the level of electromagnetic interference. The paper reviews the problem of connecting the maximum number of unconnected copper islands on the fully routed twolayer board, which has ground planes on both sides with the help of vias. An iterative algorithm is proposed based on determining the area of the projections of isolated islands with the metallization area on the opposite sideboard, if a via can be placed in the intersection area. The algorithm guarantees the connection between the maximum number of islands.

Fabrication of large scale uniform copper-island thin film for ultrasensitive surface enhanced Raman scattering

Nanostructured metals with designable and controllable structures have received increasing attention in surface enhanced Raman scattering (SERS) due to the single molecular detection limit. Great challenges still remain in creating large scale substrates with high-density ‘hotspots’ to provide a uniform and stable enhancement of Raman signals. Here, we fabricated a copper island thin film over an 80 cm2 scale substrate with tunable particle sizes by combining sputtering with dealloying processes. The island size can be tailored from 150 nm to 370 nm by controlling parameters and etching conditions and possesses an optimized surface morphology structure. The detection limit of crystal violet (CV) molecules reached 0.1 pM. Meanwhile, the copper island thin film presents good homogeneity and stability. Our method is promising to repeatedly fabricate novel metal SERS substrates on a large scale with standard properties for sensing applications.

Electrochemical Copper Deposition on Nanoscale-Sculptured Aluminum for Mechanically Stable Joints with Optimal Electrical and Heat Transport Properties

Copper is a material with a very high conductivity per volume; therefore it is widely used in the industry for nearly every electric application. However, with respect to weight aluminum (due to its low density of 2.7 g/cm3) shows a significantly higher electrical conductivity than copper. For many lightweight applications, aluminum would be the preferred material, but it lacks for good technical solutions for forming easy to apply, corrosion resistant, highly conductive contacts to (other) metals, especially to copper. Many of these problems are related to the native aluminum oxide coating on all aluminum surfaces in contact to air. State of the art solutions for electrical contacting aluminum surfaces require high temperatures and/or high pressure, thus making them expensive and typically damage the surface near microstructure of the aluminum.In this abstract, we will discuss details of a room temperature technique, which allows for a mechanically stable, corrosion resistant, galvanic copper deposition on aluminum surfaces with extremely high interface conductivity for heat as well as for electrical current. This allows the application of standard bonding technologies for copper (e.g. soldering or using conductive glues) onto aluminum as a conducting material.The copper deposition technique contains three steps: 1. A special surface preparation, i.e. nanoscale-sculpturing (cf. [1]) which creates a low corrosive aluminum surface structure full of mechanical hooks, composed of 100 crystallographic facets.2. A preconditioning step before galvanostatic copper deposition.3. Galvanic copper deposition controlling the nucleation of copper islands within the hooking structure and the morphology of the growing copper layer.Due to the nanoscale-sculpturing, the deposited copper is mechanically stable bonded to the aluminum surface. Dependent on the demands for subsequent bonding applications, the galvanic copper deposition must be adjusted; e.g. for gluing, large parts of the hook like structure from the underlying aluminum surface should still exist after a thin layer of copper is deposited.In contrast, for soldering application, a robust and thick layer of copper is needed.How the nanoscale-sculpturing and the galvanic copper deposition can be adjusted to various application will be discussed in detail.[1] Baytekin-Gerngross, M., Gerngross, M., Carstensen, J. and Adelung, R. (2016). Making metal surfaces strong, resistant, and multifunctional by nanoscale-sculpturing. Nanoscale Horizons, 1(6), pp.467-472.

Уменьшение обменного смещения, вызванное ростом эффективной толщины слоя меди в гетероструктурах NiFe/Cu/IrMn

In a series of NiFe/Cu/IrMn structures with variable effective thickness of the nonmagnetic copper interlayer (up to its absence in the NiFe/IrMn sample), decrease the exchange bias and coercivity caused by increase in the effective thickness of the copper layer is observed. Merger of copper islands at the 1 nm effective Cu thickness replaces direct exchange interaction between the ferromagnetic NiFe and antiferromagnetic IrMn to indirect exchange interaction provided by the conduction electrons through the copper layer NiFe-Cu-IrMn. The structural quality of single crystalline ferro- and antiferromagnetic layers does not undergo any change and magnetization reversal happens by coherent rotation of magnetization in the all analyzed temperature range 2 - 300 K. Simulation of the dynamics of Cu deposition demonstrates the island structure of the film at the initial stages up to effective thickness 1 nm.

Effect of Cr Contents on the Porosity Percentage, Microstructure, and Mechanical Properties of Steel Foams Manufactured by Powder Metallurgy

In this work, the effect of Cr content (0, 1, 2, 3, and 4 wt%) on the porosity percentage, cell walls microstructure, and mechanical behavior of the steel foams containing 0.6 wt% C, 1.5 wt% Cu, and 2 wt% P manufactured by powder metallurgy using leachable space holder technique was investigated. The microstructure of the cell walls was evaluated by optical microscopy (OM) and scanning electron microscopy (SEM). The mechanical behavior of the manufactured foams was studied by compression and hardness tests. The porosity values of the steel foams were between 72 and 76%, and increase in Cr content (from 0 to 4 wt%) did not have significant effect on the porosity. The results revealed that the microstructure of cell walls comprised of copper islands, intergranular carbides, phosphorus phases, and pearlite. The liquid phase sintering (LPS), solution strengthening by Cr, and the formation of intergranular carbides lead to improve the mechanical behavior of steel foams. The elastic region, long sawtooth plateau region, and fracture point are manifestly observed in the compressional stress versus strain curves. By increasing the Cr content, the plateau stress (from 41.7 to 153.2 MPa), the fracture point stress (from 42.3 to 182.4 MPa), and the elasticity modulus (from 1.23 to 3.73 GPa) increase.

Effects of copper content on microstructure and mechanical properties of open-cell steel foams

The effects of copper content on the microstructural and mechanical properties of steel foams are investigated. Spherical urea granules, used as a water-leachable space holder, were coated with a mixture of iron, ultrafine carbon, and different amounts of copper powders. After the mixture was compacted and the space holder was removed by leaching, a sintering process was performed under an atmosphere of thermally dissociated ammonia. Microstructural evaluations of the cell walls were carried out using optical microscopy and scanning electron microscopy in conjunction with energy-dispersive X-ray spectroscopy. In addition, compression tests were conducted to investigate the mechanical properties of the manufactured steel foams. The results showed that the total porosity decreases from 77.2% to 71.9% with increasing copper content in the steel foams. In the foams’ microstructure, copper islands are mostly distributed in pearlite and intergranular carbide phases are formed in the grain boundaries. When the copper content was increased from 0 to 4wt%, the elastic modulus, plateau stress, fracture stress, and fracture strain of manufactured steel foams improved 4.5, 6, 6.4, and 2.5 times, respectively.

Potential Dependent Structure and Stability of Cu(111) in Neutral Phosphate Electrolyte

Copper and copper oxide electrode surfaces are suitable for the electrochemical reduction of CO2 and produce a range of products, with the product selectivity being strongly influenced by the surface structure of the copper electrode. In this paper, we present in-situ surface X-ray diffraction studies on Cu(111) electrodes in neutral phosphate buffered electrolyte solution. The underlying mechanism of the phosphate adsorption and deprotonation of the (di)-hydrogen phosphate is accompanied by a roughening of the copper surface. A change in morphology of the copper surface induced by a roughening process caused by the formation of a mixed copper–oxygen layer could also be observed. The stability of the Cu(111) surface and the change of morphology upon potential cycling strongly depends on the preparation method and history of the electrode. The presence of copper islands on the surface of the Cu(111) electrode leads to irreversible changes in surface morphology via a 3D Cu growth mechanism.

Differential Inhibition during Cu Electrodeposition on Ru: Combined Electrochemical and Real-Time TEM Studies

The time-dependent inhibition of the copper deposition reaction on Ru surfaces was investigated electrochemically at rotating-disc Cu and Ru electrodes in the presence and absence of organic plating additives. The copper deposition rate is high on bare ruthenium. It decreases as the ruthenium surface becomes coated with copper and as the plating additives adsorb and eventually reaches the slow steady-state copper deposition kinetics on copper itself. This differential inhibition effect (DIE) of copper additives during direct electroplating on a foreign substrate (i.e. not copper) is investigated with voltammetry and potentiometry at a rotating Ru disk electrode, and compared with a rotating Cu electrode. We also use simultaneous electrochemical measurements and in situ transmission electron microscopy (TEM) to study nucleation and growth of copper islands electrodeposited on ruthenium electrodes. Combining the in situ TEM and electrochemical measurements allows us to observe the growth of individual islands in real time and establish the effects of additives on island shape and saturation island density.

Plasmonic resonances in copper island films

The optical properties of Cu island films, in particular their plasmonic behaviour, are investigated. The films are fabricated by electron beam evaporation using different deposition parameters (deposited mass thickness and substrate temperature). The optical response can be tuned from a metal-like behaviour to well-defined localized surface plasmon resonances and is well correlated with the structural and morphological properties of the samples. Significant changes of optical properties take place with sample aging, including quenching and non-monotonic frequency shift of the plasmon resonance. These changes are interpreted in terms of Cu oxidization process, that appears to strongly depend on the initial morphology of samples. Theoretical calculations in the framework of effective medium theories qualitatively explain the experimental observations. Overall, the results give a detailed insight on the morphology dependence and time evolution of the optical response of Cu island films that may provide useful guidelines for applying these nanostructures in plasmonic applications.

Exploring CO2 reduction

One promising way to lower atmospheric levels of CO2 is to convert it to something useful such as CO, a starting material for making valuable hydrocarbons. Researchers have shown that catalysts combining copper and indium can drive that conversion electrochemically, but mechanistic details have remained elusive, thwarting efforts to improve the process. By using microfabrication techniques to make highly ordered catalytic electrodes, chemists in Switzerland have uncovered new details about the active phase of the catalysts that facilitate the reaction (Nat. Commun. 2018, DOI: 10.1038/s41467-018-03980-9). Microfabrication methods usually help manufacturers make tiny integrated circuits. Javier Perez-Ramirez of ETH Zurich and coworkers used the procedures, instead, to make model electrodes patterned with millions of precisely arranged copper and indium catalytic islands. The team had suspected that some unrecognized synergistic interfacial effect involving the metals and their oxides was key to reducing CO2...

A study of dynamical evolution of small two-dimensional Copper islands’ diffusion on Ag(111) surface and observed surface effects

We study the diffusion of two-dimensional [Formula: see text] islands on Ag(1[Formula: see text]1[Formula: see text]1) surface using molecular dynamics (MD) simulations. The work is the extension of calculations of monomer and dimer Hayat et al. [Phys. Rev. B 82 (2010) 085411] and trimer results Shah et al. [Phys. Lett. A 378 (2014) 1732]. Simulations carried out at three different temperatures — 300, 500, and 700 K — show the concerted motion to be dominant for the smaller islands (2- to 4-atoms), while the shape-changing multiple-atom processes are responsible for the diffusion of larger islands. Arrhenius plots of the diffusion coefficients reveal that the effective energy barrier is less than [Formula: see text] meV for the largest island size of Cu/Ag(1[Formula: see text]1[Formula: see text]1). There is a scaling of the effective energy barrier with size to some extent, but most notably it remains constant for islands with 4- to 6-atoms. The diffusion coefficient increases within a factor of 10 at the three temperatures 300, 500, and 700 K. The observed anharmonic features of the [Formula: see text] adislands (breakage and pop–up) at Ag(1[Formula: see text]1[Formula: see text]1) surface as well as the surface anharmonicity of the Ag-substrate (fissures, dislocations, vacancy generation, and atomic exchange), are also presented. These findings can serve as an input for kinetic Monte Carlo (KMC) simulations. For the smaller sized islands the variation in the effective energy barrier with the island size is in good agreement with the experimental findings.