A Compatible and Efficient Fabrication of Bi-Continuous Nanoporous Copper Films

To cater to the application in various micro/nano devices, this paper reports a compatible and efficient approach combining electrodeposition and dealloying to fabricate bi-continuous nanoporous copper films. In the electrodeposition step, effect of concentration ratio of different ions, pH of the solution and cathode current density on the elementary composition and microscopic morphology of the deposited alloy are systematically investigated, obtaining an optimum condition with good stability and process compatibility. A uniform copper-zinc alloy with its zinc content improved to ~67 at.% is prepared under this condition. A uniform nanoporous copper with an average pore size of 150 nm is fabricated by ultrasonic assisted dealloying whose efficiency is significantly improved compared to free dealloying. This method is promising to be used in the mass production of nanoporous copper films, benefiting researches on various practical applications in micro/nano devices.

Copper(II) Perfluorinated Carboxylate Complexes with Small Aliphatic Amines as Universal Precursors for Nanomaterial Fabrication

Copper(II) carboxylate compounds with ethylamine and isopropylamine of the general formula [Cu2(RNH2)2(µ-O2CRf)4], where R = Et, iPr, and Rf = CnF2n+1, n = 1–6, were characterised in the condensed and gas phases by electron impact mass spectrometry (EI MS), IR spectroscopy, and thermal analysis. A mass spectra analysis confirmed the presence of metallated species in the gas phase. Among the observed fragments, the pseudomolecular ions [Cu2(RNH2)2(µ-O2CRf)3]+ were found, which suggests the dimeric structure of the studied complexes with axially N-coordinated ethyl- or isopropylamine molecules and bridging perfluorinated carboxylates. TGA studies demonstrated that copper transfer to the gas phase occurs even under atmospheric pressure. The temperature range of the [Cu2(RNH2)2(µ-O2CRf)4] and other copper carriers detection, observed in variable temperature infrared spectra, depends on the type of amine. The possible mechanisms of the decomposition of the tested compounds are proposed. The copper films were produced without additional reducing agents despite using Cu(II) CVD precursors in the chemical vapor deposition experiments. The layers of the gel-like complexes were fabricated in both spin- and dip-coating experiments, resulting in copper or copper oxide materials when heated. Dinuclear copper(II) carboxylate complexes with ethyl- and isopropylamine [Cu2(RNH2)2(µ-O2CRf)4] can be applied for the formation of metal or metal oxide materials, also in the nanoscale, by vapour and ‘wet’ deposition methods.

Fabrication of Antibacterial Metal Surfaces Using Magnetron-Sputtering Method

One-hundred-nanometer films consisting of silver, copper, and gold nanocrystallites were prepared, and their antibacterial properties were quantitatively measured. The magnetron-sputtering method was used for the preparation of the metallic films over the glass plate. Single- and double-layer films were manufactured. The films were thoroughly characterized with the XRD, SEM, EDS, and XPS methods. The antibacterial activity of the samples was investigated. Gram-negative Escherichia coli, strain K12 ATCC 25922 (E. coli), and Gram-positive Staphylococcus epidermidis, ATCC 49461 (S. epidermidis), were used in the microbial tests. The crystallite size was about 30 nm in the cases of silver and gold and a few nanometers in the case of copper. Significant oxidation of the copper films was proven. The antibacterial efficacy of the tested samples followed the order: Ag/Cu > Au/Cu > Cu. It was concluded that such metallic surfaces may be applied as contact-killing materials for a more effective fight against bacteria and viruses.

Study of Copper–Nickel Nanoparticle Resistive Ink Compatible with Printed Copper Films for Power Electronics Applications

This paper is focused on copper–nickel nanoparticle resistive inks compatible with thick printed copper (TPC) technology, which can be used for power substrate manufacturing instead of conventional metallization techniques. Two types of copper–nickel inks were prepared and deposited by Aerosol Jet technology. The first type of ink was based on copper and nickel nanoparticles with a ratio of 75:25, and the second type of ink consisted of copper–nickel alloy nanoparticles with a ratio of 55:45. The characterization of electrical parameters, microstructure, thermal analysis of prepared inks and study of the influence of copper–nickel content on electrical parameters are described in this paper. It was verified that ink with a copper–nickel ratio of 55:45 (based on constantan nanoparticles) is more appropriate for the production of resistors due to low sheet resistance ~1 Ω/square and low temperature coefficient of resistance ±100·10−6 K−1 values. Copper–nickel inks can be fired in a protective nitrogen atmosphere, which ensures compatibility with copper films. The compatibility of copper–nickel and copper films enables the production of integrated resistors directly on ceramics substrates of power electronics modules made by TPC technology.

UV/Ozone Treatment and Open-Air Copper Plasmonics

Thin copper films with thickness ∼28 nm deposited on SiO2 substrate with the vacuum electron beam evaporation method and treated by UV-ozone are studied. It was found that a UV-ozone treatment of the copper film causes rapid formation of the thin ∼3-4 nm oxide film. XPS analysis showed that CuO oxide predominates in this film. The formed oxide film effectively protects the copper against the following oxidation. The presented method of UV-ozone treatment is a simpler and cheaper approach compared to many other ways to form protective coatings of copper to preserve its functional properties. This method can be useful in nanoelectronic, nanooptical, and biosensors applications.

Breaking of Odd Chirality in Magnetoelectrodeposition of Copper Films on Micro-Electrodes

The surface chirality was investigated in magnetoelectrodeposition (MED) of copper films on micro-disc electrodes with the diameters of 100 and 25 µm. The MED was conducted in the magnetic fields of 1–5 T, which were parallel or antiparallel to the ionic currents. In the case of 100 µm-electrodes, the MED films prepared in 2 and 3 T exhibited odd chirality for the magnetic field polarity, as expected in the magnetohydrodynamic (MHD) vortex model. However, the films prepared in the higher fields of 4 and 5 T exhibited breaking of odd chirality. In the case of the 25 µm-electrode, the broken odd chirality was observed in 2 and 3 T. These results indicate that the strong vertical MHD flows induce the breaking of odd chirality. The mapping of chiral symmetry on the axes of the magnetic field and electrode diameter demonstrate that the odd chirality could be easily broken by the fluctuation of micro-MHD vortices.

Formation of Graphite-Copper/N-Silicon Schottky Photovoltaic Diodes Using Different Plasma Technologies

Plasma spraying and magnetron sputtering were used to form graphite–copper films on an n-type silicon surface. The main objective of this work was to compare the properties of the obtained graphite–copper Schottky photodiodes prepared using two different layer formation methods and to evaluate the influence of copper content on the surface morphology, phase structure, and photovoltaic characteristics of the graphite–copper films. Surface morphology analysis shows that the surface of the formed layers using either plasma spraying technology or the magnetron sputtering method consists of various sphere-shaped microstructures. The X-ray diffraction measurements demonstrated that the graphite–copper coatings formed by plasma spraying were crystalline phase. Meanwhile, the films deposited by magnetron sputtering were amorphous when the copper concentration was up to 9.7 at.%. The increase in copper content in the films led to the formation of Cu crystalline phase. Schottky diodes formed using magnetron sputtering technology had a maximum current density of 220 mA/cm2 at 5 V. Meanwhile, the maximum electric current density of Schottky photodiodes formed using plasma spraying reached 3.8 mA/cm2. It was demonstrated that the efficiency of Schottky diodes formed using magnetron sputtering was up to 60 times higher than Schottky diodes formed using plasma spraying.