ZrO2 films were grown on Si and SiO2 substrates in the temperature range of 250-500 degreesC using atomic layer deposition (ALD) technique. ZrI4 and H2O-H2O2 solution were used as metal and oxygen precursors. The refractive index of the 50-125 nm thick films, measured at 580 nm wavelength, varied between 2.05 and 2.25 slightly decreasing with increasing growth temperature. The film growth rate also decreased with the increase in temperature. The films contained cubic and/or tetragonal ZrO2 phases. The cubic phase was preferentially formed at relatively low deposition temperatures and in the beginning of the growth process. In addition, monoclinic ZrO2 was detected in the films thicker than 40-50 nm.