Computation of Structure and Energy of the 3 (21(-1)) Tilt Boundary in Silicon

Different experimental and+ theoretical determinations of the rigid body translation t in the Z 3 (211) tilt grain boundary in silicon aFe compared. A calculation using Keating's potential gives a t vector and an atomic structure in very good agreement with Paxton and Suttonts tight binding calculation and with experimental determinations on germanium by Bourret et al. his confirms the validity of Papon and Petit's model for the atomic structure of this grain boundary. 1 INTRODUCTION The grain boundary structure in diamond-structure semiconductors has been studied during last years by different ways from theoretical and experimental points of view. Now, it appears that the intrinsic atomic structure is not the direct origin of any special electronic structure able to explain the electronic activity observed on some grain boundaries. In particular, no states have been found in the gap o f germanium, due to dangling bonds /l/. The electronic activity of some grain boundaries in silicon is attributed to precipitates /2/. Thus the determination of the atomic structure of a grain boundary is useful to study its effects on impurity mobility and precipitation. Such atomic structure determinations have been performed by electronic microscopy (a fringes or high resolution electron microscopy) associated with theoretical models and are in agreement with reconstructed structures. These reconstructed structures do not show any dangling bond in silicon or germanium. However, some problems may arise concerning eventual disagreement between the different determinations relative to a particular grain boundary. As an example, we have chosen the 2 3 (211) tilt boundary in silicon for which a great number of studies have been published. We have compared the different structures which have been proposed. In particular, we have compared the rigid body translation they give for the displacements of the two crystals with respect to each other. With the aid of Keating's model we have calculated the rigid body translation and we have compared the results with the experimental and theoretical determinations already known. Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:1990114 COLLOQUE DE PHYSIQUE I I I $ 0 ; ; d o 0 0 O 1 1 O O 1 0 0 t o o ; 1 0 0 0