Growth of thin Al₂O₃ films on biaxially oriented polymer films by atomic layer deposition

The effects of thin film nucleation and initial growth on roughness, chemistry and thermomechanical properties of polymer film surfaces were studied. Al₂O₃ was deposited onto commercial biaxially oriented polypropylene and polylactic acid films at 80 °C by using atomic layer deposition technique. Both substrates, especially the more hydrophobic polypropylene, showed initial growth through Al2O3 clusters. There was a faster deposition of Al₂O₃ on polylactic acid film than on polypropylene at the early stages of the Al₂O₃ deposition. There were also indications of chemical interactions between polylactic acid and trimethyl aluminum used as a precursor for Al₂O₃. Changes in the thermo-mechanical properties of the polymer surfaces with Al₂O₃ also evidenced the differences between the substrate polymer films. The near surface interphase formed in polylactic acid probably contributed to the strong increase and scattering in the softening temperature during the early thin film growth