Zuzana Kučerová

Deposition of protective coatings in rf organosilicon discharges

The paper discusses the deposition of protective coatings ranging from organosilicon plasma polymers to SiO2-like films and hard diamond-like carbon/silicon oxide (DLC?:?SiOx) coatings in radio frequency capacitively coupled discharges using hexamethyldisiloxane (HMDSO). As a result of the optimization of the deposition conditions it was possible to obtain high performance protective coatings. In the HMDSO/O2 mixture, it was shown that rather than the SiO2-like film a hard cross-linked SiOxCyHz polymer film can be used as a protective coating for polycarbonate. The optimum conditions for the deposition of an almost stress-free film were 17% of HMDSO and dc bias voltage of ?240?V. The film hardness and elastic modulus were 10?GPa and 75?GPa, respectively. The refractive index at 600?nm was 1.5 and the extinction coefficient decreased from 0.02 at 240?nm down to zero at 600?nm.The films deposited from HMDSO/CH4 and HMDSO/CH4/H2 mixtures exhibited the attractive properties of DLC films with the partial elimination of some of their drawbacks, such as absorption in the visible and a high intrinsic stress. The optimum concentration of the HMDSO was approximately 21%. Under these conditions the concentration of SiOx in the films was approximately 9?at.%. The film hardness and elastic modulus were above 22?GPa and 120?GPa, respectively.

Mechanical and microwave absorbing properties of carbon-filled polyurethane.

Polyurethane (PU) matrix composites were prepared with various carbon fillers at different filler contents in order to investigate their structure, mechanical and microwave absorbing properties. As fillers, flat carbon microparticles, carbon microfibers and multiwalled carbon nanotubes (MWNT) were used. The microstructure of the composite was examined by scanning electron microscopy and transmission electron microscopy. Mechanical properties, namely universal hardness, plastic hardness, elastic modulus and creep were assessed by means of depth sensing indentation test. Mechanical properties of PU composite filled with different fillers were investigated and the composite always exhibited higher hardness, elastic modulus and creep resistance than un-filled PU. Influence of filler shape, content and dispersion was also investigated.

Structural changes of plasma deposited SiOxCyHz thin films attained by thermal annealing

The objective of the present work was to investigate the influence of thermal annealing on the optical and mechanical properties as well as on the chemical structure of plasma deposited SiOxCyHz films. The films were prepared by PECVD from HMDSO/oxygen mixtures under a wide range of deposition conditions. Their optical and mechanical properties were studied by spectroscopic ellipsometry and depth sensing indentation technique, respectively. The atomic composition was determined by RBS and ERDA measurements. FTIR analysis was used to find the densities of particular chemical bonds in the films. The annealed films exhibited changes of the refractive index and extinction coefficient. The refractive index always decreased with increasing annealing temperature. The observed increase in hardness and elastic modulus after annealing was probably correlated with dehydration of the films and an increase of Si−O−Si bonds with increasing annealing temperature.

Composition and Functional Properties of Organosilicon Plasma Polymers from Hexamethyldisiloxane and Octamethylcyclotetrasiloxane

Hybrid organic-inorganic thin films with different fractions of silicon oxide were deposited in rf capacitively coupled discharges using pure hexamethyldisiloxane (HMDSO), octamethylcyclotetrasiloxane (D4) or 5 % HMDSO in O-2. The deposition in continuous wave (cw) mode was compared with pulsed conditions under which the discharge on-time was 5 ms and the off-time varied from 0.5 to 15 ms. The chemical composition of the films was studied by FTIR, RBS and ERDA. Their optical properties in UV/visible/NIR were determined from spectroscopic ellipsometry and reflectance measurements fitted with a Kramers-Kronig consistent dispersion model based on a parametrization of density of states. Film hardness and reduced modulus were determined from depth sensing indentation tests.

Carbon nanotubes synthesized by plasma enhanced CVD: Preparation for measurements of their electrical properties for application in pressure sensor

Carbon nanotubes (CNTs) were synthesized in atmospheric pressure microwave plasma torch in the mixture of argon, methane and hydrogen on the silicon substrate with SiO2 overlayer and a thin top iron film serving as a catalyst. This deposition technique is unique because of its simplicity and high CNT growth rate but it is still under investigation as concerns exits around its reproducibility. CNTs were deposited with the future prospect of their applications or further characterization that might require CNTs in the form of suspension or powder. One of the research directions includes measurements of CNT electrical properties such as their current-voltage (I-V) characteristics. Preparation of solutions with well dispersed CNTs was studied using various liquids (distilled water, ethyl alcohol) and ultrasonication. Dried drops of these solutions were investigated by scanning electron microscopy (SEM) and atomic force microscopy (AFM) in order to assess CNT appearance and dispersion. Electrical measurement chips with gold electrodes were prepared by electron lithography. CNTs were placed on the chips by dropping their solution and the I-V characteristics may be measured by contacting the electrodes bridged by CNTs