NiO films were grown on Si (100) by atomic layer deposition using Ni (Cp) 2 (Cp= cyclopentadienyl, C 5 H 5) or Ni (EtCp) 2 [EtCp= ethylcyclopentadienyl,(C 2 H 5) C 5 H 4)] and ozone in the 150-300 C temperature range. The growth temperature dependence of structure, electronic density, and impurity levels for the prepared NiO films was studied using X-ray reflectivity, X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, time of flight-secondary ion mass spectroscopy (ToF-SIMS), and transmission electron microscopy. The behavior of films deposited using Ni (Cp) 2 and Ni (EtCp) 2 is compared and discussed. NiO films with good stoichiometry and low amounts of contaminants are obtained at a growth temperature (T g) of 250 C or above. At a fixed T g, the growth rate for NiO films deposited using Ni (Cp) 2 is higher than the one of films deposited using Ni (EtCp) 2. Furthermore, the growth rate for NiO deposited using Ni (Cp) 2 at T g= 150 C is 0.32 nm/cycle and decreases substantially in films deposited at higher temperatures. The electronic density of NiO films deposited at 300 C is close to the one of bulk NiO (1.83 e-/Å 3). According to XRD and FTIR results, films deposited at T g≥ 200 C have a simple cubic polycrystalline structure. Impurities in NiO films decrease with increasing T g, as detected by ToF-SIMS.