PbSe thin films on BaF2 (1 1 1) were grown by molecular beam epitaxy with different selenium beam flux. Evolution of PbSe surface morphologies with Se/PbSe beam flux ratio (Ri) has been studied by atomic force microscopy and high-resolution X-ray diffraction. Growth spirals with monolayer steps on PbSe surface are obtained using high beam flux ratio, R-r >= 0.6. As R-r decreases to 0.3, nano-scale triangle pits are formed on the surface and the surface of PbSe film changes to 3D islands when R-r = 0. Glide of threading dislocations in (1 1 0) {1 0 0}-glide system and Pb-rich atom agglomerations are the formation mechanism of spiral steps and triangle pits. The nano-scale triangle pits formed on PbSe surface may render potential applications in nano technology. (C) 2007 Elsevier B.V. All rights reserved.