Značajke trenja C i C:N tankih slojeva načinjenih RF magnetronskim rasprašivanjem

Carbon and C:N layers were prepared using the commercially available Leybold-Heraeus Z 550 radio frequency magnetron sputtering plant. A graphite target of high purity (99.999 % C) was used. The tribological testing was performed with a reciprocating ball-on-disc tribometer. The sliding distance on the coating was defined as the time at which a scoring occurs, and the friction coefficient exhibits an abrupt increase. From this, and from the known amplitude of the reciprocating ball, the sliding distance was evaluated.Tanki slojevi C i C:N načinjeni su u standardnom sustavu za rasprašivanje s RF magnetonom. Upotrebljavana je grafitna meta visoke (99.999 %) čistoće. Tribološka mjerenja načinjena su pomoću tribometra s kuglicom na disku. Klizni pomak na nanešenom sloju definira se preko trenutka kada nastane ogrebotina i faktor trenja naglo poraste

Reflection-based fibre-optic refractive index sensor using surface plasmon resonance

A reflection-based fibre-optic refractive index sensor using surface plasmon resonance (SPR) in a thin metal film sputtered on a bare core of a multimode optical fibre is presented. The sensing element of the SPR fibre-optic sensor is the core of a step-index optical fibre made of fused silica with a gold film double-sided sputtered on the whole core surface, including the core end face. Consequently, a terminated reflection-based sensing scheme to measure the refractive indices of liquids is realized. The sensing scheme uses a wavelength interrogation method and the refractive index of a liquid is sensed by measuring the position of the dip in the reflected spectral intensity distribution. As an example, the aqueous solutions of ethanol with refractive indices in a range from 1.333 to 1.363 are measured. In addition, the increase in the sensitivity of the SPR fibre-optic refractive index sensor with the decrease of the fibre sensing length is demonstrated.Web of Science9art. no. 1403

A comparison of different measurement methods of mechanical properties of Al thin films

The paper compares two different methods for testing of metallic thin films: microcompression test and nanoindentation. Microcompression test is one possibility how to perform mechanical tests on a very small scale. This method requires preparation of a small cylindrical specimen (micropillar) of micrometric size by FIB and execution of a compression test using nanoindenter device equipped with a flat diamond punch. Stressstrain curves of the thin films were obtained from such tests. Nanoindentation tests were then conducted to compare the results on the same films. Two different metal thin films - AlCuW, AlCuSi with thickness 2 mu m and grain size 3.8 mu m in average were prepared by PVD method. In this paper, we announce the results of measurements, a comparison of the results obtained by each method and identify advantages and limitations of the methods

Highly sensitive plasmonic structures utilizing a silicon dioxide overlayer

In this paper, simple and highly sensitive plasmonic structures are analyzed theoretically and experimentally. A structure comprising a glass substrate with a gold layer, two adhesion layers of chromium, and a silicon dioxide overlayer is employed in liquid analyte sensing. The sensing properties of two structures with distinct protective layer thicknesses are derived based on a wavelength interrogation method. Spectral reflectance responses in the Kretschmann configuration with a coupling BK7 prism are presented, using the thicknesses of individual layers obtained by a method of spectral ellipsometry. In the measured spectral reflectance, a pronounced dip is resolved, which is strongly red-shifted as the refractive index (RI) of the analyte increases. Consequently, a sensitivity of 15,785 nm per RI unit (RIU) and a figure of merit (FOM) of 37.9 RIU-1 are reached for the silicon dioxide overlayer thickness of 147.5 nm. These results are in agreement with the theoretical ones, confirming that both the sensitivity and FOM can be enhanced using a thicker silicon dioxide overlayer. The designed structures prove to be advantageous as their durable design ensures the repeatability of measurement and extends their employment compared to regularly used structures for aqueous analyte sensing.Web of Science1218art. no. 309

One-dimensional photonic crystals with different termination layer thicknesses and very narrow Bloch surface wave and guided wave based resonances for sensing applications

We demonstrate an efficient sensing of both gaseous and aqueous analytes utilizing Bloch surface waves (BSWs) and guided waves (GWs) excited on a truncated one-dimensional photonic crystal (1DPhC) composed of six TiO2/SiO2 bilayers with a termination layer of TiO2. For the gaseous analytes, we show that 1DPhC can support the GW excited by an s-polarized wave and the theoretical shift of the resonance wavelength is linear for small changes in the analyte refractive index (RI), giving a constant RI sensitivity of 87 nm per RI unit (RIU). In addition, for the aqueous analytes, the GW excited by s-polarized and BSW by p-polarized waves can be resolved and exploited for sensing applications. We compare two designed and realized 1DPhCs with termination layer thicknesses of 60 nm and 50 nm, respectively, and show experimentally the differences in their very narrow reflectance and phase responses. An RI sensitivity and figure of merit as high as 544.3 nm/RIU and 303 RIU-1, respectively, are obtained for the smaller thickness when both s- and p-polarized BSWs are excited. This is the first demonstration of both very deep BSW-based resonances in two orthogonal polarizations and a very narrow resonance in one of them.Web of Science98art. no. 56

Simulation of the discharge propagation in a capillary tube in air at atmospheric pressure

International audienceThis paper presents simulations of an air plasma discharge at atmospheric pressure initiated by a needle anode set inside a dielectric capillary tube. We have studied the influence of the tube inner radius and its relative permittivity ε r on the discharge structure and dynamics. As a reference, we have used a relative permittivity ε r = 1 to study only the influence of the cylindrical constraint of the tube on the discharge. For a tube radius of 100 µm and ε r = 1, we have shown that the discharge fills the tube during its propagation and is rather homogeneous behind the discharge front. When the radius of the tube is in the range 300 to 600 µm, the discharge structure is tubular with peak values of electric field and electron density close to the dielectric surface. When the radius of the tube is larger than 700 µm, the tube has no influence on the discharge which propagates axially. For a tube radius of 100 µm, when ε r increases from 1 to 10, the discharge structure becomes tubular. We have noted that the velocity of propagation of the discharge in the tube increases when the front is more homogeneous and then, the discharge velocity increases with the decrease of the tube radius and ε r. Then, we have compared the relative influence of the value of tube radius and ε r on the discharge characteristics. Our simulations indicate that the geometrical constraint of the cylindrical tube has more influence than the value of ε r on the discharge structure and dynamics. Finally, we have studied the influence of photoemission processes on the discharge structure by varying the photoemission coefficient. As expected, we have shown that photoemission, as it increases the number of secondary electrons close to the dielectric surface, promotes the tubular structure of the discharge

Funkčnost amorfních uhlíkových povlaků s obsahem křemíku deponovaných použitím nízkotlaké PECVD

Amorphous carbon films with silicon content were deposited using low pressure PECVD. The films were optimised for deposition on steel substrates. To evaluate the impact resistance of graded amorphous carbon films in dynamic loading wear applications an impact test has been used

SMV-2015-33: Investigation of the local microstructure changes caused by dynamical indentation of the coatings

The aim of the contracted research was to study the mechanical properties of the coatings deposited on high speed steel substrate. The classification of the coatings was performed using an impact tester our own construction in a dynamic mode and enabled us to predict the limit load causing the coating destruction

SMV-2017-28: Examination of local microstructural changes caused by dynamic indentation of the nanolaminate coatings

Method of analysis of the coated materials under dynamic impact load was performed using impact tester developed at the Institute of Scientific Instrumentation in Brno. Dynamical impact testing leads to identification of deformation and fatigue mechanisms of nanostructured and nanolaminated coatings. The impact force-imprint depth dependencies were interpreted with respect to the coating microstructure and computed simulation of indentation

SMV-2013-29: Deposition technology and implementation of multilayer system

We have developed deposition technology and implementation of multilayer system of molybdenum and silicon prepared by magnetron sputtering. Interface roughness has to be smaller than 0.2 nm and reproducibility of bilayer thickness (i.e. molybdenum and silicon) must be better that 0.1nm. This multilayer system was used as a mirror in x-ray laser PALS