Ionized physical vapor deposited Al2O3 films: Does subplantation favor formation of α-Al2O3?

The broad energy distributions of the condensing particles typically encountered in ion assisted vapor deposition techniques are often a drawback when attempting to understand the effect of the energetic bombardment on the film properties. In the current study, a monoenergetic Al beam generated by a filtered cathodic arc discharge is employed for the deposition of alumina (Al2O3) films at well defined AI ion energies between 4 eV and 200 eV at a substrate temperature of 720 degrees C. Structural analysis shows that Al energies of 40 eV or larger favor the formation of the thermodynamically stable zeta-Al2O3 phase at the expense of other metastable Al2O3 polymorphs. The well defined ion energies are used as input for Monte-Carlo based simulations of the ion surface interactions. The results of these simulations reveal that the increase of the Al+ ion energy leads to an increase in the fraction of ions subplanted into the growing film. These findings underline the previously not considered role of subsurface processes on the phase formation of ionized physical vapor deposited Al2O3 films. (C) 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim