Tiny structural flaw discovered that limits coating strength in high-tech materials
Researchers found that ultra-thin protective coatings used in cutting tools and semiconductors can only stay intact up to a critical thickness—about 4 nanometers—before they crack and lose strength. The discovery explains why manufacturers can't simply make these coatings thicker for better performance, which could reshape how companies design industrial components.
Originaltitel: Interface controlled microstructure evolution in nanolayered thin films
<p>X-ray nano-diffraction and transmission electron microscopy were conducted along the thickness of a similar to 4 pm thick CrN/AlN multilayer with continuously increasing AlN layer thicknesses from similar to 1 to 15 nm on similar to 7 nm thick CrN template layers. The experiments reveal coherent growth, large columnar grains extending over several (bi-)layers for thin AlN layer thicknesses below similar to 4 nm. Above similar to 4 nm, the nucleation of the thermodynamically stable wurtzite structured AlN is favored, leading to coherency breakdown and reduction of the overall strains, disrupting the columnar microstructure and limiting the maximum grain size in film growth direction to the layer thickness. (C) 2016 Acta Materialia Inc. Published by Elsevier Ltd.</p>