Abstract : Growth of functional oxides in thin films has been very important in the last fifteen years. For microelectronic and spintronic applications, it is of interest to synthesise crystalline films, with a thickness of few nanometers and with very sharp interfaces. In that case, properties of thin films are dominated by interface effects. This study deals with the LI-MOCVD growth of iron based oxides: Fe3O4, g-Fe2O3 and BiFeO3. Thin film growth of these compounds has been investigated. The originality of this work comes from the UHV AFM in situ investigations. We refer to these studies to analyse the influence of growth parameters on the first growth stages.