Zirconium doped zinc oxide thin films were deposited by reactive chemical pulverization spray pyrolysis technique on heated glass substrates at 400 degrees C, 450 degrees C and 500 degrees C using zinc and zirconium chlorides as precursors. The effect of zirconium dopant and surface roughness on the nonlinear optical properties was investigated using atomic force microscopy (AFM) and third harmonic generation (THG). The best value of susceptibility chi((3)) was obtained from the doped films with less roughness. A strong third order nonlinear optical susceptibility chi((3)) = 20.49 x 10 (12) (esu) of the studied films was found for the 5% doped sample at 450 degrees C. (C) 2009 Elsevier B. V. All rights reserved.