Jan Janča

Plasma modification of polycarbonates

Abstract We deposited protective coatings on polycarbonates from hexamethyldisiloxane (HMDSO) and HMDSO/O2 mixtures by the plasma enhanced CVD method. In particular, we studied deposition rate, optical constants in UV/VIS, film composition and mechanical properties dependent on rf power and oxygen to HMDSO flow rate ratio. Plasma polymer HMDSO films (PP-HMDSO) showed good transparency in the visible and increased absorption in UV region. The optical constants of HMDSO/O2 films were similar to the tabulated SiO2. In general, the films were characterised by a relatively high content of hydrogen (22–66%) and a carbon content below 20%. The films deposited at an oxygen-to-HMDSO flow rate ratio higher than 15 exhibited higher tensile stress and higher hardness than those prepared at ratios of 5–10. The nature of the internal stress changed to compressive for PP-HMDSO. Plasma pre-treatment of polycarbonate in argon significantly improved the film adherence, especially when low powers and short treatment times were used.

INVESTIGATION OF THE CHEMICAL ACTION OF THE GLIDING AND POINT ARCS BETWEEN THE METALLIC ELECTRODE AND AQUEOUS SOLUTION

The plasma–solution interaction processes for gliding and “point” arcs between the aqueous solution surface and the metal electrode in the gas phase are studied. The plasma, liquid, and surface zones are taken into consideration. The electric field strength is measured, and the gas and electron temperatures and ion composition are estimated for the plasma zone. The cathode fall, water vaporization rate, and active species current yield due to the radiation chemistry mechanism are determined for the surface zone. The efficiency of oxidation of iodine ions and organic dyes by different types of discharge in the liquid zone are investigated. The difference in action of the various discharge types may be connected with various influences of the plasma and surface zone on the oxidation processes.

Temperature dependence of mechanical properties of DLC/Si protective coatings prepared by PECVD

One of the main problems of amorphous diamond-like carbon (a-C:H or DLC) films deposited by plasma-enhanced chemical vapor deposition (PECVD) is their poor thermomechanical stability. The thickness of the films is limited to a few hundreds of nanometers in order to guarantee stable coatings. It is shown that major improvements in the mechanical properties of DLC films can be obtained if hexamethyldisiloxane is added in the gas mixture used for DLC deposition. The mechanical properties of hard protective DLC/Si films deposited by PECVD from an argon-methane-hexamethyldisiloxane mixture have been analyzed using microindentation techniques as the main experimental characterization tool. The formation and development of crack lines and patterns have been studied in order to determine the fracture toughness of the film and of the interface as a function of temperature.

HF plasma pencil- new source for plasma surface processing

The high-frequency plasma pencil is a source of a highly active environment (electrons, ions, reactive radicals, excited atoms and molecules), which can be generated at atmospheric, reduced or increased pressure, preserving a broad control of performance. As an active medium flowing through the plasma jet a gas, a liquid as well as a mixture of dispersed particles (powders) can be used. The plasma jet can be controlled like hand-operated tools. Several technological applications have already been used (restoration of archeological glass artifacts, fullerene production, fragmentation of molecules for microelectrophoresis, plasma polymerization in liquids, various plasma surface treatments, etc.).

Wool treatment in the gas flow from gliding discharge plasma at atmospheric pressure

A new method of wool plasma surface treatment at atmospheric pressure employing the stable gas flow excited in gliding electrical discharge (called GlidArc) has been developed. The plasma from a small space between electrodes is drifted by the gas flow into a conic space, towards the base of which, the treated combed top moves. The subjective handle of the treated combed top is unchanged and the whiteness and the dye sorption are increased.

Characterization of silicon oxide thin films deposited by plasma enhanced chemical vapour deposition from octamethylcyclotetrasiloxane/oxygen feeds

Abstract Plasma enhanced chemical vapour deposition (PECVD) of thin oxide films was investigated, changing electrical potential conditions at the substrate electrode (dc, rf coupled or positive biased). Rf discharge at the frequency of 13.56 MHz was generated in a planar reactor with two internal electrodes. Silicon substrates were placed on the powered electrode. The octamethylcyclotetrasiloxane (OMTS) was chosen as a source of OSiO groups in order to test new possibilities in the silicon oxide depositions. The reflectance in the visible, the transmittance in the infrared region, X-ray photoelectron spectra (XPS) and Rutherford backscattering method (RBS) analyses were applied to describe the deposition rate, the optical properties, the composition and the structure of the deposited films. The comparison among these four methods concerning the film composition and structure is discussed. The pronounced changes in the deposition rate with rf power or dc bias typical of every electrical potential condition were observed. However, other film characteristics seemed to be very similar. The film optical parameters and the atomic composition were close to those of amorphous silicon dioxide.

Protection Coatings for Polycarbonates based on PECVD from Organosilicon Feeds

Abstract We deposited protective films by plasma enhanced chemical vapour deposition (13.56 MHz) on polycarbonate and silicon substrates from tetraethoxysiloxan or hexamethydisiloxan mixed with oxygen and argon. The thickness and optical parameters of the films were calculated from the measured reflectance in the visible. The film growth rate changed from 2 to 50 nm/min. In most of the deposition conditions used, the films were nonabsorbing in the visible. The Vickers microhardness of the system film-polycarbonate was measured in the load range 5–1000 mN. The calculated film hardness was from 500–1000 HV. Three factors were essential for higher film hardness in addition to a higher deposition rate: the ratio of the monomer flow rate to the oxygen one was higher than ten, slightly elevated substrate temperature to about 70 °C and negative bias from − 200 V.

Correlation between SiOx content and properties of DLC:SiOx films prepared by PECVD

Hard diamond like carbon (DLC) films with an addition of SiOx were deposited in capacitively coupled rf discharges from a mixture of methane and hexamethyldisiloxane (HMDSO). The flow rate of HMDSO was changed in order to vary the SiOx content in the films. Complete atomic composition of the films was determined by Rutherford backscattering spectroscopy combined with elastic recoil detection analysis. The thickness and the optical properties were obtained from the ellipsometric measurements. The mechanical properties were studied by a depth sensing indentation technique using Fischerscope H100 tester. The O/Si ratio in DLC:SiOx films was 0.286 and the content of SiOx increased with the HMDSO-to-methane flow rate ratio q. The DLC:SiOx films were close to DLC films as concerning the optical properties in the uv/visible and the high hardness if q was maximum 0.25. However, the compressive stress in the films was reduced, the film fracture toughness was improved and the deposition rate increased.

A Plasma Surface Treatment of Polyester Textile Fabrics Used for Reinforcement of Car Tires

Polyester tire cord surfaces have been modified by plasma at low temperature and atmospheric pressure. The surface treatment has been executed by various nonequilibrium discharges, namely by barrier discharge, atmospheric pressure glow discharge and gliding arc. The polymeric multicord sewing threads treated by this procedure have been used in the same form as in industry, i.e., with the protecting oil films on their surface. The surface properties have been investigated by electron spin resonance spectroscopy and by measuring their contact angle with various liquids; partially the zeta potential measurements have been used, too. Further tests have been done at an industrial testing impregnation line using the common technology and conditions, on both plasma treated and untreated fibers. Finally, the standard H-tests and peel-tests have been used to characterize the fiber adhesion to usual testing rubbers.

Optical characterization of diamond like carbon films using multi-sample modification of variable angle spectroscopic ellipsometry

Abstract In the first part, thicknesses and spectral dependences of the optical constants of the diamond like carbon (DLC) films were determined without any parameterization in the range 240–830 nm by multi-sample modification of variable angle spectroscopic ellipsometry (VASE). DLC films were prepared by plasma enhanced chemical vapor deposition (PECVD) onto silicon single crystal substrates. It was shown that the influence of some defects of the DLC films on the optical constants is suppressed by applying the method of multi-sample modification of VASE. In the second part, the spectral dependences of the determined optical constants were interpreted using a recently developed model of dispersion based on the modified Lorentz oscillator. Two modified Lorentz oscillators corresponding to both π→π* and σ→σ* interband transitions were taken into account. Within this model of dispersion of the optical constants, the concept of the band gap and the existence of localized energy states within the band gap were taken into account as well.