Preparation of single crystal faces by electrodeposition

In addition to flame annealing methods for the preparation of single crystal faces of metals with extended atomically smooth terraces [5.10-5.13], the already traditional technique of electrolytic growth of single crystals [5.6-S.9] has remained unrivaled for the preparation of perfect, screw dislocation-free faces or faces with single, isolated screw dislocations.  

The technique developed by Budevski et al. [5.6-5,9] is based on one hand on the fact that under certain conditions, particularly higher concentrations and elevated temperatures, single crystals can be electrochemically grown to develop large single 

A perfect crystal face should be completely free of any surface defects. In view of its further application for crystal growth studies, however, a face not intersected by screw dislocations can be considered conditionally as perfect. All other defects have either little or no effect on the growth behavior of the face. To meet this situation, the term quasi-ideal or quasi-perfect has been introduced for the description of faces free of screw dislocations [5.14]. A quasi-perfect face is characterized by extended atomically smooth terraces separated by monatomic steps and absence of emergence points of screw dislocations. A smooth quasi-perfect face without steps can be described as an intact quasi-perfect face . 

For the purpose, an appropriately oriented cylindrical single crystal with a diameter of ca. 0.3 cm and a length of ca. 2 cm is enclosed in a glass tube ending as a capillary in its bottom part. The assembly is then placed in an electrolytic cell and used as a cathode against an anode of the same material as shown in Fig. 5.3. 

F re 5.3 Schematic representation of an electrolytic cell for the investigation of the growth of Ag single crystal faces. A plane parallel bottom window allows the microscopic observation of the growing front face of the crystal in the glass capillary. 

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