Self-structuring in Zr1-xAlxN nanocomposites films: a material system with diverse structuresWednesday (26.09.2018) 15:30 - 15:45 S1/03 - 23 Part of:
To advance functional hard coatings with tailored properties including superhardness, toughness, thermal stability ultrawear resistance and corrosion protection one can tune coherency strain and elastic modulus difference between different domains forming via self-organized nanostructuring in the wider family of transition metal (TM) aluminum nitride materials. Here we present, nanostructure formation via surface-diffusion-mediated segregation of highly immiscible ZrN and AlN in Zr1−xAlxN(0≤x≤1) films during high mobility growth conditions. The large immiscibility combined with interfacial and strain energy balance resulted in a superhard nanolabyrinthine lamellar structure with well-defined (semi) coherent c-ZrN and w-AlN domains of sub-nm to ~4 nm (controlled by mobility) in 0.2≤x≤0.4 films. For high AlN contents (x>0.49) Al-rich ZrN domains attain wurtzite structure within fine equiaxed nanocomposite wurtzite lattice. Slow diffusion in wurtzite films points towards crystal structure dependent driving force for decomposition.
The self-organization occurs during ion assisted magnetron sputter deposition of Zr1−xAlxN films grown on to single-crystal and polycrystalline substrates. To discern the segregation route and phase evolution, single-phase (cubic/hexagonal) and fully-segregated two-phase films are deposited with various compositions and growth temperatures. We present a comprehensive structural and chemical analysis and discuss the mechanisms governing the formation of diverse nanostructures in the entire compositional range. Particularly, the driving force to self-organize nanostructures in cubic and hexagonal systems is discussed combined with first principles calculations. In addition, we establish relationship between nanostructures and mechanical strength of the films.