A Structural Model for the Interface between Amorphous and Crystalline Si or Ge.
HARVARD UNIV CAMBRIDGE MASS DIV OF ENGINEERING AND APPLIED PHYSICS
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A general procedure for building static models of interfaces, which involves a change in phase-specific construction rules at the boundary plane, is outlined. Its application to tetrahedrally coordinated materials shows that an amorphous-crystalline interface model can be created by replacing the chair - type sixfold rings typical of the crystal by a mixture of different ones typical of the amorphous phase. The interface consists of two crystalline and two amorphous layers. The detailed topologies, bond angle distortions, and radial distribution functions for each of the four layers are reported. The surface tension has a large energetic component due to the excess strain energy in both the amorphous and crystalline interface layers. For Ge the estimated surface tension is 0.235Jsq m. This is used to show that the model, which contains no dangling bonds, represents a state of minimum energy. Application to the problem of creating a model for amorphous Ge by connecting randomly oriented crystallites with a random network matrix shows that such a model consists of more than 80 random network. Finally it is pointed out that the interface model is a starting point for a detailed description of the crystallization process.
- Solid State Physics