Growth steps and 2D nuclei are observed by AFM on the {001} faces of MnHg(SCN)(4)(C2H6OS)(2) (MMTD) crystals. Measurements of the heights of steps and nuclei show the lowest value is equal to c/4. According to the interplanar distance modification established by Donney and Harker, the lowest height should be c/2. Appearance of the sub-layer growth is correlative with the crystal structure of MMTD. (c) 2005 Published by Elsevier B.V.