Nanorelief of the Surface of Thin Films of Al–Mn and Al–Ni Alloys upon Ion-Assisted Deposition on Glass

Abstract

The patterns of structure formation, as well as the wettability, were investigated for thin films of aluminum and Al–2.1 at % Mn and Al–1.4 at % Ni alloys on glass substrates prepared by ion beam-assisted deposition. The application of scanning probe microscopy (SPM) and scanning electron microscopy allowed characterizing nano- and micrometer-sized topographic heterogeneities on the film surfaces and studying the nature of their wettability measured by sessile drop method. Within the framework of the profile and topographic approaches for the analytical analysis of SPM images, a set of discrete roughness parameters was used, supplemented by dimensionless parameters-complexes (ψ and k) and a parameter-function of probability density of the heights and valleys of the surface nanorelief. The proposed research hybrid parameter k characterizes the shape of the irregularities of the nanorelief profile, has visibility and relates to the amplitude and roughness step. The informativity of the system of nine selected parameters for estimating the roughness and irregularity of the local structure of the film surface in the cross-section and longitudinal section was shown, which allowed not only studying numerically structural-morphological changes during aluminum doping, but also determining the quantitative relationships between the microgeometry of film surface and the deposition conditions. The effect of the initial relief of the glass substrate on the parameters of the surface irregularities of the films, which, as obtained, have the form of submicron cones and local hillocks, was revealed. The Gaussian distribution of the film nanorelief of aluminum and its alloys over the surface area was obtained, and the coating surfaces could be considered as a realization of a random normal process. The frequency distributions of the microdroplet fraction by size were lognormal. The film roughness parameters were found to correlate with the size and density of droplet fraction microparticles. It was revealed that the deposition of Al-containing films reduced the surface hydrophilicity of the film/glass substrate system. When doping aluminum, the degree of morphological heterogeneity of the film surface, as well as their wettability, decreased. The homogeneous regime of film wetting with water and its dependence on the material, morphology, and chemical composition homogeneity of the surface are discussed.