Thermal stability and phase transformations of γ-/amorphous-Al 2O3 thin films

Abstract

Magnetron-sputtered Al2O3 thin films were annealed in ambient air. The phase compositions of the as-deposited Al2O 3 films were (i) fully amorphous, (ii) nanocrystalline γ-Al2O3 in an amorphous Al2O3 matrix, and (iii) fully crystalline γ. For all samples, annealing to 1100-1150 °C resulted in a transformation to α-alumina. The transformation paths depend on the phase fraction of γ in the as-deposited films. For amorphous films and films with low initial γ fraction, the intermediate phase θ-Al2O3 appeared in the range of 1000-1100 °C. For predominantly crystalline γ-Al2O 3 as-deposited films no intermediate Al2O3 phases were observed, indicating a direct γ-to-α phase transformation at -1100 °C. © 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.