Abstract
The paper summarizes current knowledge of growth defects in physical vapor deposition (PVD) coatings. A detailed historical overview is followed by a description of the types and evolution of growth defects. Growth defects are microscopic imperfections in the coating microstructure. They are most commonly formed by overgrowing of the topographical imperfections (pits, asperities) on the substrate surface or the foreign particles of different origins (dust, debris, flakes). Such foreign particles are not only those that remain on the substrate surface after wet cleaning procedure, but also the ones that are generated during ion etching and deposition processes. Although the origin of seed particles from external pretreatment of substrate is similar to all PVD coatings, the influence of ion etching and deposition techniques is rather different. Therefore, special emphasis is given on the description of the processes that take place during ion etching of substrates and the deposition of coating. The effect of growth defects on the functional properties of PVD coatings is described in the last section. How defects affect the quality of optical coatings, thin layers for semiconductor devices, as well as wear, corrosion, and oxidation resistant coatings is explained. The effect of growth defects on the permeation and wettability of the coatings is also shortly described.
Highlights
The surface topography is an important characteristic of physical vapor deposition (PVD) thin films because it determines their functional performance in many applications
The seeds for nodular defects can form from: (a) geometric irregularities on the substrate surface after mechanical pretreatment; (b) substrate irregularities arising from ion etching; and (c) foreign particles that arrived on the substrate surface before or during the coating growth
We identified the origins of the growth defects found in PVD coatings prepared by three different
Summary
The surface topography is an important characteristic of physical vapor deposition (PVD) thin films because it determines their functional performance in many applications. PVD techniques, such as magnetron sputtering, electron beam evaporation, cathodic arc deposition, ion beam deposition, pulsed laser deposition (PLD) and others, generate substantially different types and density of seed particles and different shape, size, and density of growth defects. A few years earlier, studies of Spalvins and Brainard [10] demonstrated that nodules in thick metallic films are nucleated by substrate surface imperfections arising from asperities, pits, dust particles, and flakes. The particularity of the approach of our research group was that we pinpointed selected defects on the coating surface and followed them through the tribological test with scanning electron microscopy (SEM) and a focused ion beam (FIB) microscope [42,43]. In the last chapter we explore the influence of growth defects on the functional properties of PVD coatings
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