High resolution electron microscopy of grain boundaries in Nb₃Ge‐films

Abstract

SUMMARY Nb3Ge‐films synthesized on Mo‐substrates by the co‐evaporation method show a characteristic fabric with a quasi‐twelvefold symmetry around the [001]‐axis of the A15‐type cubic structure. Among approximate +30°‐ and ±60°‐rotation boundaries, grain boundaries having rotation angles between 28° and 29° are observed most frequently in the Nb3Ge‐films. Using the high resolution electron micrographs, a Σ17‐boundary having an ideal rotation angle of 28.07° is analysed and plausible boundary models on the atomic level are proposed.

Electron microscopy of grain boundaries of Nb3Ge with the A15 structure

“…Straight 217 [001]/28.07° tilt boundaries were always on (410)-planes of both grains forming a boundary [7]. This feature is also recognized in Fig.…”

“…A similar relations is seen, for example, in grain boundaries of Ge [8]. The possible structure models of the 217 boundary were compared with the observed HRTEM images [7].…”

“…The boundaries have generally more complicated shapes than is evident from these examples, cf. [7]. In Fig.…”

“…l a . By measuring the positions of bright spots in many HRTEM images, the authors of [7] obtained the relative translation of the lattices and constructed an interpenetrating pattern (IP pattern) of lattices, in which the coincident site lattice (CSL; e.g. [11 to 141) and the 0-lattice [l, 21 were superimposed.…”

“…The high angle tilt boundaries of Nb3Ge grains in QTF regions were studied in detail by Nissen et al [7]. Following these results, the boundaries are classified into three different types on the basis of the orientation of the boundary plane.…”