The morphology, density and thickness of SiO2 layers grown on silicon are determined by neutron reflectivity. The validity of different oxidation models is examined using the neutron reflectivity determined thickness for different growth times and temperatures in conjunction with those available in the literature on ellipsometry data. Two of the oxidation models fit all the data sets very well without the incorporation of a fast initial growth. All the data sets give energy of diffusion of 2.1 ± 0.1 eV and the chemical reaction activation energy of 1.86 ± 0.08 eV
