Atomic relaxation and dynamical generation of ordered and disordered chemical vapour infiltration (CVI) SiC polytypes

Gerard L. Vignoles (1)

1 LCTS - Laboratoire des Composites Thermostructuraux

The coexistence of ordered and disordered polytypes in SiC deposits is discussed from the point of view of their formation under CVD/CVI conditions, i.e., far from equilibrium. Local deformations at layer n are considered to determine the orientation and the deformations of the (n + l)th layer. An analysis of this dependence is made by constructing a first return map of an atomic relaxation variable, based on the ab initio calculation data for some regular polytypes made by Cheng et al., J. Phys. (Condens. Matter) 2 (1990) 5115. Orientation sequences are linked to the local deformation parameter, and to 29Si and 13C NMR shifts. iterations of this map are considered as a one-dimensional dynamical system simulating layer-by-layer growth. Depending on control parameters, the dynamical system exhibits stationary, periodic or chaotic orientation sequences, reproducing many experimentally obtained polytypes. The occurrence of CVD- or CVI-grown one-dimensionally disordered polytypes can thus possibly arise from a deterministic process able to yield also regular structures for nearby values of control parameters.

Mots clés: Silicon carbide; polytypism; modeling

Domaines: Cristallographie; Matériaux

Gerard L. Vignoles. Atomic relaxation and dynamical generation of ordered and disordered chemical vapour infiltration (CVI) SiC polytypes. Journal of Crystal Growth, 1992, 118 (3-4), pp.430-438. ⟨10.1016/0022-0248(92)90092-W⟩. ⟨hal-00327296⟩