Thermal Stability and Phase Transformations of γ-/Amorphous-Al2O3 Thin Films

• Magnetron-sputtered Al2O3 thin films were annealed in ambient air. The phase compositions of the as-deposited Al2O3 films were (i) fully amorphous, (ii) nanocrystalline γ-Al2O3 in an amorphous Al2O3 matrix, and (iii) fully crystalline γ. For all samples, annealing to 1 100-1 150 °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 1 000-1 100 °C. For predominantly crystalline γ-Al2O3 as-deposited films no intermediate Al2O3 phases were observed, indicating a direct γ-to-α phase transformation at ≈1 100 °C.

Nyckelord

annealing

atomic force microscopy (AFM)

faceting

sputtering

X-ray diffraction (XRD)

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