Copper coatings were deposited on monocrystalline Si substrates using a magnetron discharge with a liquid cathode in the metal vapour plasma. During the deposition, the bias voltage in the range from...

We examined the feasibility of alumina substrate metallization by magnetron deposition of copper coatings with thickness of several tens µm for its prospective applications in production of ceramic PCBs and packaging. The films were prepared in magnetron sputtering systems with cooled and thermally insulated (hot) targets. Substrates with different geometries were used, including those with through-holes. Thickness, adhesive properties, and electrical resistivity of produced coatings were analyzed. If the film thickness exceeded ~20 µm, we observed its systematic delamination, unless the dedicated Cu_xO_y sub-layer of was introduced between the substrate and the main Cu film. Intermediate copper oxide films were investigated separately by SEM, EDS, and XRD methods, and deposition conditions for predominant growth of favorable tenorite CuO were determined. Prepared composite two-layer CuO + Cu coatings with total thickness of ~100 µm demonstrated good adhesion to alumina substrates in scratch-testing and performed much better than Cu-only films both in soldering and thermal cycling tests. We discuss an approach for constructing a reliable metallizing coating by plasma-assisted PVD methods that could be beneficial for complex-shaped ceramic PCBs and packaging.

Research of the tungsten “fuzz” emission properties and dielectric strength was carried out. A “fuzzy” sample was made through He+ ion exposure of an initially polished tungsten surface using an inductively coupled plasma (ICP) facility. The eventual He+ ion fluence was $\sim 1.7\times 10^{25}\,\,\text{m}^{-2}$ . The induced nanostructured layer thickness was estimated to be $\sim 1~\mu \text{m}$ . The measurements were performed with an automated experimental setup developed. The setup was operated under the control of the programmable DAC/ADC module “LCard E20-10.” As a result, the untypical behavior of a nanostructured cathode in comparison with an ordinary field emissive cathode was registered. Instability of the W “fuzz” emission properties was demonstrated. Typical values of the electric field enhancement factor were found to be in the range of ~120–200 both before a single breakdown and after it. These values are in agreement with the estimations of the enhancement factor performed with taking into account the geometry of protrude cathode structures. Stabilization of the emission properties after the breakdown was observed. The conditioning effect of the nanostructured cathode was found to take place after approximately five breakdowns. After conditioning, an asymptotic value of a breakdown electric field strength was $\sim 8.5\times 10^{7}$ V/m, which is in agreement with the one for an ordinary tungsten cathode. The conditioning effect and the emission current stabilization are believed to be due to the destruction of the nanostructure under the impact of the breakdowns.

Tungsten fuzz layers formed on the plasma-facing material surfaces of thermonuclear facilities due to helium ion irradiation are known to promote the initiation of electrical discharges on the first wall. Previous studies have indicated increased arcing probability under helium ion irradiation in steady plasmas with increasing ion energy to several hundred eV. Here, we experimentally consider the growth of nanostructures on tungsten surfaces in an RF He plasma and the spontaneous initiation of arcs when applying the pulsed bias voltage to the sample, up to several keV. The arc current and voltage waveforms were obtained, and the scanning electron images of the arc traces were analyzed. The behavior of the arc at the smooth/fuzzy surface boundary directly demonstrated the beneficial arcing conditions of the nanostructured layer. The proposed approach of pulsed biasing enables controlling the amount and duration of arcs for better analysis of their dimensions and dynamics. From the experimental results, the total arc trace length and arc velocity were calculated and compared with literature data, giving a good agreement both between experiments and theoretical data and between experiments in different arc initiation conditions.