Article ID Journal Published Year Pages File Type
8032926 Thin Solid Films 2018 28 Pages PDF
Abstract
Metastable Ti1−xAlxN films have the more outstanding functional properties in the range of composition around x = 0.6 for their use as protective coatings. They exhibit complex texture because of the phase transition between TiN-like rocksalt and AlN-like wurtzite structures. The competitive growth between cubic and wurtzite domains is studied in metastable Ti0.38Al0.62N thin film deposited by reactive magnetron sputtering for thicknesses between 1 and 3.7 μm. Long-range order is analysed within the film by X-ray diffraction and cross-sectional TEM imaging. The study is complemented by using Ti K-edge diffraction anomalous spectroscopy to obtain differentiated information on short-range order around Ti atoms incorporated in cubic and wurtzite domains. The growth along the [111]c direction has the effect of promoting the appearance of crystallites with wurtzite symmetry oriented along [001]h. In the middle of the layer, cubic and wurtzite domains become coherently oriented. Lattice distortions, which affect long- and short-range order, are revealed by the anisotropy of broadening of the diffraction lines and by spectroscopic data collected on the main diffraction lines. The fine pre-edge structure indicates a strong distortion of the tetrahedral sites occupied by Ti atoms along the c axis, which minimizes the in-plane lattice mismatch. Near the film surface, a dramatic change in growth directions is observed. A better understanding of the structural transition mechanism in the (Ti,Al)N system could help improve the mechanical performances of these coatings in the future.
Related Topics
Physical Sciences and Engineering Materials Science Nanotechnology
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