Study on the atomic and electronic structure in mono- and multi-layers of nitride films

Transition metal nitrides have found wide-spread applications in the cutting- and machining-tool industry due to their extreme hardness, thermal stability and resistance to corrosion. The increasing demand of these nitrides requires an in-depth understanding of their structures at the atomic level. This has led to numerous experimental and theoretical researches [1-3].

Here, we report recent results on the atomic and electronic structures of metal nitride thin films (CrN, VN and TiN) on MgO and Al₂O₃ substrate using advanced TEM and theoretical calculations. The study on the effect of defects (vacancy, interfaces) in the metal nitrides film has led to some interesting conclusions. In the second part, the study on the multilayers of CrN/AlN will be demonstrated. The multilayer structure shows a peak hardness of ～40 Gpa and low friction coefficient by optimizing the bilayer period (Λ). The improvement in mechanical properties is related to the existence of metastable face-centred cubic (fcc) AlN phases, which can epitaxially stabilize in thin films. The mechanism of superior mechanical property will be revealed via a close study of dislocation density and alternative strain fields in the multilayers [4].

[1]. Z. L. Zhang et al, Physical. Review B 82(R)(2010)060103-4

[2]. Z. L. Zhang et al, Journal of Applied Physics, 110(2011)043524-4

[3]. Z.L. Zhang et al, Physical Review B 87 (2013) 014104-9.

[4]. Thanks are given to Paul H.Mayrhofer (TU Wien), Rostislav Daniel and Christian Mitterer (Montanuniversität Leoben) in Austria for delivering the film materials.