Hard coatings are commonly used in decorative applications due to their attractive colors and high wear resistance. In most cases only intrinsic colors of the coatings are exploited. Such colors are determined by the stoichiometry of the coating and can be varied only in a limited range. In this paper we demonstrated a more flexible concept of color design by exploiting interference effect between semi-transparent coating and reflective substrate. We designed a bi-layer structure with thin film of partially transparent hard coating deposited over a material with specific reflectivity (substrate or another thin film). Such construction enabled us wide control of colors since the interference-based colors can be tuned by the thickness of coating and by the optical constants of coating and the substrate (or reflective layer). The principle was demonstrated with the commonly used hard coating materials. A single-layer of AlTiN was deposited by magnetron sputtering on substrates with different reflectivity: TiN, stainless steel and Si. Colors of high saturation, ranging from yellow, pink, violet to blue, were prepared by varying the thickness of AlTiN in the range of 20-55 nm. Interference based colors normally change with the angle of observation, however, using semi-transparent coating only a small color shifts were observed. Such color design is useful in applications where both protective and decorative functionality are required.
COBISS.SI-ID: 27762471
In magnetron sputtering the material is deposited on the areas that are in direct line-of-sight of the vaporization source. If application requires coverage of substrate over its whole substrate area then the substrates have to be rotated around several axes. In the industrial deposition systems this is achieved with turntable that performs planetary-type of rotation. The substrate rotation and the target arrangement, therefore, determine the uniformity of the deposited material. When materials are deposited from different targets simultaneously then coatings can be prepared in a layered structure; in such a case, the rotation and the target arrangement also determine the layer structure, which strongly affects its elasto-plastic properties of coating. In this paper we used previously developed simulation of coating growth in deposition system with a planetary rotation to analyze the influence of the rotation and the target arrangement on the uniformity and the periodicity of layered coatings. Results of simulations showed that highly periodic modes of rotation, which are determined by the turntable gear ratio and the switch angle, cause large non-uniformities both in the thickness and the composition of layered coatings. On the other hand, less periodic modes of rotation produce better coating uniformity although for certain rotation parameters large non-uniformities may also occur. It was shown that exact periodicity of layered coatings can be calculated from the least common multiple of revolution times around individual axes. Computer simulation is useful tool for the design of new PVD systems that require high deposition uniformity. The simulation has attracted interest of researchers and several companies, and resulted in signing a research contract with one of the largest German manufacturers of PVD systems for deposition of hard coatings.
COBISS.SI-ID: 26959655