Pb(Zr,Ti)O3 (PZT) thin films for ferroelectric probe data storage technology were studied. (001)-oriented PZT thin films were deposited on SrRuO3/SrTiO3 substrates by rf magnetron sputtering. Dc voltage was applied on the films using a metal-coated tip and the poling region was observed by scanning nonlinear dielectric microscopy (SNDM). The contrasts in the positive and negative poling regions in the SNDM images obtained were improved by using the PZT films after ion-beam irradiation. This suggests that a surface layer of a few nanometers in thickness was formed on the as-grown PZT film and the polarization was not invertible in the surface layer. The deposition condition was examined with focus on deposition temperature. Nanosized domain dots were successfully formed on a PZT film deposited at 550 °C.