We have investigated the formation and growth of nano sized ripple topography on ZnO thin films by 10 keV O1+ bombardment at impact angles of 80 degrees and 60 degrees, varying the ion fluence from 5 x 10(16) to 1 x 10(18) ions/cm(2). At 80 degrees the ripples are oriented along the ion beam direction whereas at 60 degrees it is perpendicular to the ion beam direction. The developed ion induced structures are characterized by atomic force microscopy (AFM) and the alignment, variation of rms roughness, wavelength and correlation length of the structures are discussed with the existing model and basic concept of ion surface interaction. (C) 2011 Elsevier B. V. All rights reserved.