Bilayer period dependence of CrN/CrAlN nanoscale multilayer thin films

CrN/CrAlN nanoscale multilayer thin films with a bilayer period (λ) ranging from 4.4 to 44.1 nm were deposited on Si wafers (100) by closed field unbalanced magnetron sputtering (CFUBMS). The λ of the layers was controlled by the rotation speed of the substrate holder. The coatings were characterized by high resolution X-ray diffraction and field emission transmission electron microscopy. The CrN/CrAlN nanoscale multilayer thin films exhibited a CrN (200) and AlN (200) crystalline orientation. Nano-indentation testing revealed a hardness ranging from 37 to 46 GPa according to the bilayer period. The highest hardness was obtained with a bilayer period of 5.5 nm due to the high resistance to plastic deformation.