Epitaxial crystallization INDEX

Electron diffraction from these crystals indicated a high degree of crystallinity in both the trimer and polymer, and indexing of the patterns required the use of new unit cells different from the usual structures(Figure 4). X-ray diffrac-tometry was used to provide structural information about the third dimension in these epitaxially crystallized films. It should be noted that the characteristic spacing determined by X-ray diffrac-tometry is the b-axis, only if the unit cell is orthorombic (Table II). 

The orthogonal projection of the epitaxial poly(DMDA) could not be indexed using the unit cell data for the bulk polymerized crystal (8). However, poly(DMDA) cannot usually be polymerized to completion or to high crystallinity in the bulk due to cross-linking. The use of an epitaxial substrate may have controlled the polymerization process that led to oriented single crystals. 

The following three mechanisms are suggested for the growth of a guest crystal in an epitaxial relation on the surface of low-index faces of a host crystal. 

A.J. Melmed and N.D. Shinn. Nucleation and Epitaxial Growth of Cr Crystals on Stepped W Surfaces with Low-Index Facets. Surf. Sci. 193 475 (1988). 

---