Unit cell step structures on vapour-grown Cr 2S 3 single crystals

Abstract

Step structures on the (001) plane of as-grown crystalline Cr 2S 3 that had been prepared by the chemical vapour deposition method have been observed by interference contrast microscopy. Two kinds of steps, with heights of 10.1 and 5.1 Å were found. These are respectively due to the unit cell and a half of the unit cell of the crystal. Unit cell steps were seen to occur successively from a screw dislocation with Burgers vector normal to the surface equal to half of a unit cell. The generated steps with height equal to a half of the unit cell coagulated soon into a step with height of one unit cell. By passing other screw dislocations on the surface the unit cell steps combine with them just as expected from the screw dislocation model for monomolecular steps. The unit cell steps split spontaneously into half unit cell steps forming a fork-like step structure. The successively drawn out forking structure weaves an interlaced step pattern on the surface. However, the two interlaced steps annihilate when they meet.