We have investigated the initial growth of Sn and Ge1-xSnx layers on Ge( 0 0 1) surface by using scanning tunneling microscopy. After the growth of a 0.035 ML-thick Sn layer at room temperature, Sn clusters lining vertically to a dimer row was observed. In the case of the 0.035-0.018 ML-thick Sn growth at 250 degrees C, the characteristic surface reconstruction with the step-edge undulation like a comb was observed. In the growth of a Ge0.994Sn0.006 layer at 250 degrees C, the multilayer polynuclear growth with a lot of two-dimensional small domain was observed. These surface reconstructions should be accounted for by the large compressive stress induced in the surface layer due to the incorporation of Sn atoms. (c) 2008 Elsevier B.V. All rights reserved.