Influence of Al content on the phase formation, growth stress and mechanical properties of TiZrAlN coatings

Quaternary (Ti,Zr)(1- x)AlxN transitionmetal nitride films, with Al content x ranging from 0 to 0.37, were reactively sputter-deposited from individual metallic targets under Ar + N-2 plasma discharges on Si substrates at T-s = 270 degrees C. The influence of Al addition on the crystal structure, phase formation, growth morphology and intrinsic stress development, electrical and mechanical properties was systematically investigated. Three distinct compositional regions were evidenced: i) for 0 <= x <= 0.07, films develop a columnar structure consisting of cubic TiZr(Al)N grains with (111) and (200) preferred orientation, large compressive stresses up to similar to-4 GPa and hardness increase from similar to 20 to similar to 24 GPa, ii) for 0.09 <= x <= 0.16, Al incorporation favors the growth of nanocomposite films consisting of (200)- oriented cubic TiZr(Al) N nanocrystals surrounded by a highly-disordered matrix, accompanied by a decrease of compressive stress, whereas a maximum hardness H similar to 27 GPa and H/E ratio of 0.105 is reached at x similar to 0.12 and x = 0.14, respectively, and iii) x>0.16, XRD amorphous films are formed, with reduced mechanical properties. The structure-stress-properties relationship is discussed based on evolutionary growth regimes induced by incorporating a high-mobility metal in a refractory compound lattice. (c) 2013 Elsevier B.V. All rights reserved.