[Back]

R Hahn, M. Bartosik, H. Riedl, H. Bolvardi, S. Koloszvári, P.H. Mayrhofer:
"X-ray nano-diffraction demonstrating microstructural evolution and formation limits of CrN/AlN superlattice thin films";
Talk: 63. Metallkunde Kolloquium, Lech am Arlberg; 2017-04-18 - 2017-04-21; in: "63. Metallkunde Kolloquium - Book of Abstracts", (2017), 30.

Coherently grown nanolayered CrN/AlN thin films, referred as CrN/AlN superlattice systems, exhibit a peak in indentation hardness depending on their bilayer period. Thereby, a key factor ensuring this beneficial superlattice effect is the stabilization of the metastable cubic (B1) structure of AlN by epitaxial growth on cubic (B1) CrN.
In this contribution, we investigated formation constraints of c-AlN as well as the microstructural evolution of a 4 μm thick CrN/AlN multilayer structure with increasing thickness of AlN layers (from 1 to 15 nm) on 7 nm CrN template layers. Therefore, X-ray nano-diffraction experiments -using KB-mirror focused monochromatic synchrotron radiation with an incident energy of 14.9 keV- were conducted. The sample was a cross section lamella, mechanically grinded and polished to a thickness of 50 μm. This experiment revealed the existence of c-AlN layers up to an individual layer thickness of ~4 nm, as well as coherent growth of large columnar grains over several bilayers. AlN layers exceeding this value crystallize in the thermodynamically stable wurtzite structure. The overall strain is reduced and the maximum grain size in film growth direction is limited to the layer thickness due to the loss of coherent growth. These findings were cross validated and complemented by high-resolution transmission electron microscopy investigations.