Spiral growth and (110) twins in Bi2Sr2CaCu2Oy crystals

Atomic force microscopy (AFM), X-ray diffraction, polarized microscopy and scanning electron microscopy (SEM) were used to characterise Bi2Sr2CaCu2Oy (Bi-2212) single crystals grown at the surface of KCl. The crystals growth were mainly controlled by a spiral growth mechanism. Morphologies of the growth spirals varied with growth conditions. Single, double and even multi-spirals with square and polygonized shapes were observed. (110) growth twins were found to co-exist with square shape single or multi-spirals and lead to the square shape growth spirals. The widths and heights of growth steps were determined to be 0.5-6 mu m and 3-5 unit cells by AFM.