Epitaxial growth of PbSe thin film on BaF2(111) is studied by means of scanning tunneling microscopy (STM). The results showed that the structures and morphologies of PbSe thin films depend crucially on Pb-to-Se atomic ratio in the growth of PbSe film. For the PbSe film grown with an atomic ratio of Pb/Se approximate to 1 at a substrate temperature of 450 degrees C, the morphologies are dominated by two interlocked spirals around threading dislocation. Meanwhile, for the PbSe film grown with a higher Pb-to-Se atomic ratio, besides some spirals structures, the V-defects appear in the film. PbSe growth on BaF2(111) is in the step-flow mode, and the formation of the V-defects in the case of the PbSe film growth with a higher Pb-to-Se atomic ratio can be attributed to excessive Pb atoms congregating in the dislocation core area and relatively slow growth rate of (100) facets. (c) 2006 Elsevier B.V. All rights reserved.