Microstep structures on prismatic faces of vapour grown NbSe 4I 0.33 crystals

Abstract

The microstep line structures on the prismatic faces of vapour grown NbSe 4I 0.33 crystals are observed with an interference contrast microscope. On the {110} faces, microsteps are 6.7 Å high, while on the {100} faces the step heights are 9.5 Å or one half of 9.5 Å. The microsteps are generated either at the crystal edges or at screw dislocations. The step lines show a tendency to line up parallel to the c-axis. The step line structures reflect anisotropy of the lattice based on long columnar molecules. In the neighbourhood of screw dislocation emergence points, the growth step spirals are noticeably elongated. Micrographs of typical step patterns are presented here together with a discussion of the crystal growth process.