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Abstract:
Patterning of lines of holes on a layer of positive photoresist SXAR-P3500/6 (Allresist GmbH, Strausberg, Germany) spin-coated on a quartz substrate is carried out by using scanning near-field optical lithography. A green 532 nm-wavelength laser, focused on a backside of a nanoprobe of 90 nm diameter, is used as a light source. As a result, after optimization of parameters like laser power, exposure time, or sleep time, it is confirmed that it is possible to obtain a uniform nanopattern structure in the photoresist layer. In addition, the lines of holes are characterized by a uniform depth (71–87nm) and relatively high aspect ratio ranging from 0.22 to 0.26. Numerical modelling performed with a rigorous method shows that such a structure can be potentially used as a phase zone plate.

Keywords:
optical lithography, photoresist, quartz, hole nanopatterning

Abstract:
In the presented paper a coating of SiC particles with a metallic layer were used to prepare copper matrix composite materials. The role of the layer was to protect the silicon carbide from decomposition and dissolution of silicon in the copper matrix during the sintering process. The SiC particles were covered by chromium, tungsten and titanium using Plasma Vapour Deposition method. After powder mixing of components, the final densification process via Spark Plasma Sintering (SPS) method at temperature 950C was provided. The almost fully dense materials were obtained (> 97.5%). The microstructure of obtained composites was studied using scanning electron microscopy as well as transmission electron microscopy. The microstructural analysis of composites confirmed that regardless of the type of deposited material, there is no evidence for decomposition process of silicon carbide in copper. In order to measure the strength of the interface between ceramic particles and the metal matrix, the micro tensile tests have been performed. Furthermore, thermal diffusivity was measured with the use of the laser pulse technique. In the context of performed studies, the tungsten coating seems to be the most promising solution for heat sink application. Compared to pure composites without metallic layer, Cu-SiC with W coating indicate the higher tensile strength and thermal diffusitivy, irrespective of an amount of SiC reinforcement. The improvement of the composite properties is related to advantageous condition of Cu-SiC interface characterized by well homogenity and low porosity, as well as individual properties of the tungsten coating material.

Keywords:
metal matrix composites, silicon carbide, metallic layers deposition, thermal conductovity, interface strength

Abstract:
This paper describes the process of obtaining Cu-SiC-Cu systems by way of spark plasma sintering. A monocrystalline form of silicon carbide (6H-SiC type) was applied in the experiment. Additionally, silicon carbide samples were covered with a layer of tungsten and molybdenum using chemical vapour deposition (CVD) technique. Microstructural examinations and thermal properties measurements were performed. A special attention was put to the metal-ceramic interface. During annealing at a high temperature, copper reacts with silicon carbide. To prevent the decomposition of silicon carbide two types of coating (tungsten and molybdenum) were applied. The effect of covering SiC with the aforementioned elements on the composite's thermal conductivity was analyzed. Results were compared with the numerical modelling of heat transfer in Cu-SiC-Cu systems. Certain possible reasons behind differences in measurements and modelling results were discussed.

Keywords:
copper matrix composites, silicon carbide, interface, thermal conductivity, modelling