Vertically protruding out nano structures of PbTe are synthesized by ion beam mixing of Te/PbO bilayer using 100 MeV Ag ions. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) of pristine and irradiated samples are performed to study surface structures. Power spectral density (PSD) spectra of the structures at different fluences have been determined from AFM micrograph. The values of roughness and growth exponent, deduced from PSD, are far from any universality classes. Results distinctly indicate the unstable growth and rapid roughening of surface under swift heavy ion (SHI) bombardment. (C) 2012 Elsevier B.V. All rights reserved.