Growth and thermal stability of TiN/ZrAlN: Effect of internal interfaces

Abstract

Wear resistant hard films comprised of cubic transition metal nitride (c-TMN) and metastable c-AlN with coherent interfaces have a confined operating envelope governed by the limited thermal stability of metastable phases. However, equilibrium phases (c-TMN and wurtzite(w)-AlN) forming semicoherent interfaces during film growth offer higher thermal stability. We demonstrate this concept for a model multilayer system with TiN and ZrAlN layers where the latter is a nanocomposite of ZrN- and AlN- rich domains. The interfaces between the domains are tuned by changing the AlN crystal structure by varying the multilayer architecture and growth temperature. The interface energy minimization at higher growth temperature leads to formation of semicoherent interfaces between w-AlN and c-TMN during growth of 15 nm thin layers. Ab initio calculations predict higher thermodynamic stability of semicoherent interfaces between c-TMN and w-AlN than isostructural coherent interfaces between c-TMN and c-AlN. The combination of a stable interface structure and confinement of w-AlN to nm-sized domains by its low solubility in c-TMN in a multilayer, results in films with a stable hardness of 34 GPa even after annealing at 1150 °C.Peer ReviewedPostprint (author's final draft

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

“…Similar morphology and electron diffraction as of x = 0.75 was recorded for Zr 0.43 Al 0.57 N film deposited at 700 °C in identical conditions as are used in this work (see Fig. 3 in 30 ). Combining this information with present XRD analysis, we assume that for x > 0.55 films exhibit identical wurtzite nanocomposite morphology with varying d-spacing depending on Al content.…”

“…Experimental findings of w-ZrAlN in this work is an important result as it opens the possibility of formation of metastable zincblende/wurtzite structures of ZrN with group-IIIA–N alloys, in particular Zr 1− x In x N alloys, as the interatomic distances of ZrN and InN in the zincblende and wurtzite structures are very close 45 . Moreover, further understanding of electronic structure of w-Zr 1− x In x N will also help to underline the mechanisms behind alleged slow diffusion in these films which has direct impact on extreme thermal stability and mechanical integrity during high-temperature operations 13 , 30 , 46 .…”

Thermal and mechanical stability of wurtzite-ZrAlN/cubic-TiN and wurtzite-ZrAlN/cubic-ZrN multilayers

“…In addition, the thermal stability of the interfaces could also play an important role here since the c-111||w-0001 type of interfaces has been calculated as the lowest total energy compared with isostructural and heterostructural interfaces for both TiN/AlN and ZrN/AlN multilayer systems [45]. The heterogeneous nature of the Ti(Zr)N-sublayers is expected to cause areas where the coherency is lost during annealing resulting in a lower degree of coherency compared to the as-deposited state.…”

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

“…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. [24].…”