Abstract
The dependences of the surface roughness and the phase structure of compound thin films on substrate temperature and flux of incoming particles are investigated by a proposed mathematical model. The model, which describes physically deposited thin compound film growth process is based on the Cahn–Hilliard equation and includes processes of phase separation, adsorption, and diffusion. In order to analyze large temperature range and assuming deposition of energetic particles, the diffusion is discriminated into thermal diffusion, radiation-enhanced diffusion, and ion beam mixing. The model is adapted to analyze surface roughness evolution during film growth. The influences of the substrate temperature and incoming flux particles on the surface roughness are determined by a series of numerical experiments. The modelling results showed that the surface roughness increased as the substrate temperature rose. Besides, a similar relationship was discovered between substrate temperature and size of nanoparticles formed in binary films, so the increase in the surface roughness with the substrate temperature was attributed to the increase in size of nanoparticles.
Highlights
Nanocomposite materials, due to their promising and exceptional mechanical, thermal, optical, electrical, electrochemical, and catalytic properties, have attracted the great attention during the past few decades [1,2,3,4,5,6]
Since the phase structure determines the properties of nanocomposite materials, it is important to understand the influence of growth conditions on the phase structure of films, which can provide a better understanding of how to control the phase structure of nanocomposites and reveal the mechanisms resulting in the formation of various phase structures
The modelling results showed that the surface roughness of thin films increased with an increase in the substrate temperature
Summary
Nanocomposite materials, due to their promising and exceptional mechanical, thermal, optical, electrical, electrochemical, and catalytic properties, have attracted the great attention during the past few decades [1,2,3,4,5,6] Those properties of nanocomposites may be notably different than those of the individual constituents [1]. Nanocomposites can exist in various morphological forms such as randomly or evenly distributed nanoparticles (of various shapes), columns, or layers [7] Their multi-phase morphology may result in characteristics that are independent from the properties of each individual constituent present in the system, which provides a large range of applications [7] and creates the possibilities of varying their chemical and physical properties as a function of particle size, shape, and composition [2,8,9,10,11]. The experimental measurement of surface roughness became common procedure for Coatings 2020, 10, 1077; doi:10.3390/coatings10111077 www.mdpi.com/journal/coatings
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