Kutsay O. The scientific basis of forming of improved and high-quality functional purpose carbon films

The thesis is devoted to the relationship between process conditions and parameters for carbon condensates of different origins, their structural characteristics and properties. The carbon film condensates obtained by chemical vapor deposition method and physical vapor deposition have been investigated. It was defined areas of the operating parameters for deposition of polimer-like, diamond-like and graphite-like carbon condensates, as well as the factors which determine their physical properties by the basis of the obtained results. The systematic studies have shown that the optimal physical properties and high operating performance have carbon films deposited at an average ion energies from 80 to 120 eV. This range is due to the threshold of defect in diamond (~90 eV). The formation of nanostructures in the matrix of tetrahedral carbon (ta-C) films induced by ion beam implantation at high doses has been studied by high-resolution transmission electron microscopy (HRTEM), transmission electron diffraction (TED) and Raman spectroscopy. The ta-C films were deposited by a filtered cathodic vacuum arc (FCVA) and subsequently implanted by carbon ion beams extracted from a metal vapor vacuum arc (MEVVA) ion source. The carbon ions were implanted to doses ranging from 3 1016 to 3 1017 ions/cm-2. In accord with the thickness of ta-C films and ion ranges required the ion energy was determined to be within a range of 25 to 50 keV. The analysis of Raman spectra indicates that originally abundant sp3 carbon atomic bonding of ta-C is gradually converted to a graphitic phase during the course of ion bombardment. The local order, growth and clustering the sp2 bonded carbon atoms in the ta-C films by ion implantation is also indicated by Raman spectroscopy. However, the analysis of implanted amorphous carbon films on an atomic scale shows the formation of structure with the higher degree of order. The graphitic basal planes are formed preferably along the ion tracks. The results are discussed in the context of previously reported studies of implanted ta-C films and glassy carbon. It has been shown a critical damage level of 0.24 displacements per atom when the onset of the transformation occurs and demonstrated that the initially amorphous phase with short ordered sp3 bonding configuration can be nanostructured to the higher degree of an ordered structure using proper ion energies and doses. The sessile-drop experiment was conducted to analyze the wetting characteristics of the different amorphous carbon films before and after the plasma treatment. Initially in the carbon film-distilled water system the average contact angles have been measured within the values range from 50° to 70°. The plasma treatment of different allotropic carbon forms by low energetic ions increases very strongly the solid/liquid surface energy and reduces the contact angle down to 0°. Kinetics of water spreading on the surface of solid phases of various carbon materials has been first studied with the use of high-speed video filming (up to 1200 frames per second). It has been found that rates of low-temperature liquid and metal melts spreading and wetting the surface of solid phases are close in time (the process length is 10 2-10 3s) and in both the cases the spreading occurs in an inert mode. It has been shown that at the final stages the spreading of low-temperature liquids occurs at a viscous mode (10-30 min) caused by the presence of an adsorbed layer (coat) on the solid phase surface due to the environment. The measurements of capillary forces on different diamond-like materials and carbon allotropic modifications taken using a scanning force microscope have been discussed. The amplitude-frequency characteristics of the nanorelief surfaces studied have been widely varied by plasma chemical treatments. The measurements of capillary forces have been compared with the macroscopic values of a wetting angle. It has been shown that a macroscopic wetting angle depends on the averaged surface energy only and is slightly dependent on the nanorelief characteristics, and nanocapillary forces correlate with both surface relief parameters and the local angle of wetting. Criteria for multimeniscus mode of capillary forces measurement in the surface force spectroscopy and the prospects of this procedure application for mapping the real surface energy have been considered in detail. Impedance spectra in a 2.5 M H2SO4 solution and kinetic characteristics of reactions in the Fe(CN)6 3-/4- redox system are measured for thin-film electrodes of tetrahedral amorphous carbon (ta-C). After an anneal in a vacuum at 700 to 900 °C or implantation of C+ ions (10 15 to 10 17 ion/cm 2), ta-C films acquire electrochemical activity, which can be explained by an increased content of sp2 oriented carbon bonds. In the majority of modern infrared spectral (IR) interference multilayer coatings (MLC), conventional film-forming materials (FFM) of fluoride and chalcogenide types are used. Such coatings are characterized by relatively low mechanical strength and stability against enhanced humidity and, therefore, require surface protection. Our present results support the view that mechanical strength of these MLCs can be improved by applying a diamond-like carbon (DLC) film as an external layer. Nanoindentation measurements show that the addition of a DLC film to ZnSe/BaF2/Y2O3 IR antireflection MLC increases the combined hardness of the coatings from 0.5 to 5.0 GPa. The formation of an indent on the upper and subsequent layers of MLC has been studied by SEM and X-ray spectrum microanalysis. The resistance of DLC films applied onto MLC against light irradiation, organic solvents as well as against environmental factors was also studied. Atomic force microscopy (AFM) was used to study variations of the surface morphology of the initial MLC components before and after DLC film deposition. The practical result of studies have been made by the design of multilayer coatings with improved performance for the IR range from traditional FFM and both protective, as well as optical by functional antireflective layers of diamond-like carbon, wherein the complex nanohardness increases from 0.3 to 8.0 GPa.