We report on the atomic layer deposition (ALD) of MnO and NiO thin films on Si(100) using Mn(EtCP)(2) [EtCp = ethylcyclopentadienyl, (C2H5)C5H4] and Ni(EtCp)(2) in the temperature range of 150-300 degrees C. H2O or O-3 is selected as oxygen source for the depositions. The growth temperature (T-g) and oxygen source impact on the structure, electronic density, and impurity concentration for the as-grown MnO and NiO films have been studied using X-ray reflectivity, (XRR), grazing incidence X-ray diffraction (GIXRD), and Fourier transform infrared (FTIR) spectroscopy. A steady growth rate of 0.024-0.025 nm/cycle for the films grown using Mn(EtCP)(2) and H2O was observed in the T-g range of 250-300 degrees C. FTIR does not show any carbon impurities in the MnO films grown with H2O. The films grown using Mn(EtCp)(2) and O-3 at 300 degrees C exhibit poor adhesion on Si(100). NiO films with low amounts of contaminants are achieved using O-3 and at a T-g of 250 degrees C or above. The growth rate, however, is very high for films deposited at T-g = 150 degrees C and decreases significantly in films deposited at higher temperatures. In addition, no film growth was observed for the Ni(EtCp)(2)/H2O process. The as-grown MnO and NiO films prepared using H2O and O-3 as oxidizer, is shown, by GIXRD a polycrystalline cubic structure. (C) 2008 Published by Elsevier B.V.