Surface nanorelief of thin films of Al–Mn and Al–Ni Alloys in the case of ion-assisted deposition on glass

Abstract

The patterns of structure formation and the wetting of thin films of aluminum and its Al–2.1 at % Mn and Al–1.4 at % Ni alloys deposited onto glass substrates with assistance by self ions are studied. Nanoscale and microsized topographic inhomogeneities on the film surface are characterized by scanning probe microscopy (SPM) and scanning electron microscopy (SEM) and their wetting characteristics are measured by the sessile-drop method. Within the profile and topographic approaches to the analysis of SPM images, a set of discrete roughness parameters supplemented by dimensionless complex parameters and probability-density-function parameters of the protrusions/depressions of the surface nanorelief is used. The proposed hybrid research parameter k characterizes the shape of nanorelief profile irregularities, is comprehensible, and relates the amplitude to the roughness step. The system of nine selected parameters is shown to be informative for estimating the roughness and irregularity of the local structure of the film surface in transverse and longitudinal cross sections, which makes it possible not only to numerically study the structural and morphological changes upon the alloying of aluminum, but also to determine quantitative relationships that relate the microgeometry of the film surface to the film deposition conditions. The effect of the initial relief of the glass substrate on the parameters of film surface inhomogeneities that have the shapes of submicrometer cones and local protuberances is revealed. The Gaussian distribution of the film nanoreliefs of aluminum and its alloys over the surface area is obtained, and the film surfaces can be considered as an implementation of a random normal process. The frequency distributions of the microdroplet fraction over particle sizes are lognormal functions. A correlation is found between the roughness parameters of the films and the size and density of microparticles of the droplet fraction. It is found that the deposition of Al-containing films reduces the hydrophilicity of the surface of the film–glass substrate system. Upon the alloying of aluminum, the degree of morphological inhomogeneity of the film surfaces and their wettability decrease. The homogeneous regime of film wetting with water and its dependence on the material, the morphology, and the homogeneity of the chemical composition of the surface are discussed.