EX SITU ATOMIC FORCE MICROSCOPY STUDIES OF GROWTH MECHANISMS OF MANGANESE MERCURY THIOCYANATE CRYSTALS

Growth mechanisms of the {110} planes of the manganese mercury thiocyanate, MnHg ( SCN )4 (MMTC), crystals have been investigated by using atomic force microscopy (AFM). The results show that spiral dislocation controlled mechanism and two-dimensional (2D) nucleation mechanism operate simultaneously during growth. 2D nuclei are found to cover up the outcrop of dislocation hillocks. Pairs of circular 2D nuclei appear on the wider steps terraces and the slope of 2D nucleation islands. Hillocks introduced by both simple spiral dislocation sources and 2D nucleation are elliptical in shape. It is determined the long sides orientate along the c-direction or the direction about 45° to the c-axis. Anisotropic growth hillocks and isotropic 2D nuclei coexist on the surface, which may be due to unequal supersaturations in the mother solution during the evaporation process.