The present paper deals with the characterization of plasma polymerized allylamine films. The films were characterized using a large panel of techniques such as Fourier transformation infrared spectroscopy, X-ray photoemission spectroscopy and ellipsometry. The film microstructure was investigated as a function of the deposition power while other process parameters (gas mixture flow, pressure) were kept constant. The microstructure shows a strong dependence on the deposition power. A power transition has been identified outlining two deposition modes in agreement with a growth model developed for carbon nitride thin films. Conditions of deposition closed to this transition provide a film microstructure interesting for absorption and adhesion of biomolecules i.e. high NH2 content, high porosity and high deposition rate.