Self-structuring in Zr1−xAlxN films as a function of composition and growth temperature

Abstract

Nanostructure formation via surface-diffusion-mediated segregation of ZrN and AlN in Zr1−xAlxN films during high mobility growth conditions is investigated for 0 ≤ × ≤ 1. The large immiscibility combined with interfacial surface and strain energy balance resulted in a hard nanolabyrinthine lamellar structure with well-defined (semi) coherent c-ZrN and w-AlN domains of sub-nm to ~4 nm in 0.2 ≤ × ≤ 0.4 films, as controlled by atom mobility. 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 findings of unlikelihood of iso-structural decomposition in c-Zr1−xAlxN, and stability of w-Zr1−xAlxN (in large × films) is complemented with first principles calculations.

Interface bonding of Zr1−xAlxN nanocomposites investigated by x-ray spectroscopies and first princi

“…Concerning the film hardness behavior, our present spectroscopic results provide support for earlier assumptions made for the phase composition and hardening mechanisms [11]. It was shown [11] that Zr1-xAlxN films exhibits an increasing hardness with increasing Al content reaching a maximum for x=0.36 from where it decreases.…”

“…The large broadening of the peaks is an indication of reduced c-ZrN grain sizes (nano-crystallites or a smaller average domain size) as the peak widths are inversely proportional to the crystallite size [23]. Previous studies indicated that starting from x=0.2, the ZrAlN system has a two-phase structure [24] [11]. With increasing Al content, the Zr1-xAlxN solid solution (x=0, 0.12, 0.26) gradually transforms to a nanocomposite (x=0.4-0.55) with a characteristic two-phase laminated structure described in ref.…”

“…In the case of Zr1-xAlxN alloys, which have an even larger miscibility gap than Ti1-xAlxN solid solutions, these are difficult to stabilize and instead two-phase systems tend to form already during deposition. The strong driving force for decomposition results in a large variety of microstructures that primarily are determined by the growth temperature and Al content [10] [11]. Common to all of these alloys is that the nature of the interatomic bonding and electronic structure are affected by the alloy composition and that they change during decomposition.…”

“…In this study we have chosen Zr1-xAlxN for alloy nitride materials model system to probe changes in electron structure and chemical bonds as functions of alloy composition and formation of internal interfaces. The growth and resulting microstructures of the studied Zr1-xAlxN alloys have been reported in detail elsewhere, primary using X-ray diffractometry (XRD) and transmission electron microscopy (TEM) [10] [11]. At high Al contents a two-phase nanocomposite is formed consisting of cubic ZrN (space group Fm3m, B1, 225) and hexagonal AlN (wurtzite, space group P63mc, B4, 186) with chemically sharp semi-coherent interphases.…”

Atom Probe Tomography of Hard Nitride and Boride Thin Films

“…The Zr0.69Al0.31N films of Paper III were, on the other hand, grown using substrate rotation [50], while the deposition of the diborides of Papers IV and V were stationary.…”