Stabilization criteria for cubic AlN in TiN/AlN and CrN/AlN bi-layer systems

作者：Chawla Vipin^*; Holec David; Mayrhofer Paul H

来源：Journal of Physics D: Applied Physics , 2013, 46(4): 045305.

DOI：10.1088/0022-3727/46/4/045305

We combine the finite element (ABAQUS) and ab initio methods to study and predict the equilibrium critical thickness up to which the metastable cubic (c) AlN phase is energetically favoured to the stable wurtzite (w) variant in TiN/AlN and CrN/AlN bi-layer systems. The results show that the w-AlN phase is preferred for all thicknesses in the free-standing configuration (without a substrate) when grown on TiN, while 4 nm thick c-AlN is predicted for CrN bi-layer material systems. The substrate helps to stabilize c-AlN up to 15.8 nm, and for an incoherent interface between the substrate and the TiN or CrN interlayer, the stabilization mechanically supports the interlayer against relaxation. For a coherent interface to the substrate, a small lattice constant (as, e.g., in the case of Al substrate) helps to stabilize c-AlN, whereas a large lattice constant (as, e.g., in the case of MgO) promotes w-AlN. Finally, we predict that %26lt; 1 1 1 %26gt; orientated specimens allow for thicker c-AlN layers than those grown along the %26lt; 1 0 0 %26gt; direction.

• 出版日期2013-1-30