| Abstract |
Alumina thin films were prepared by pulsed DC reactive magnetron sputtering using operating pressures that
were varied from 3 to 20 mTorr. The films were immersed in DI water at temperatures of 55 ◦C and 65 ◦C for 30
min to study their hydrolysis corrosion behaviors. Unlike bulk crystalline Al2O3 materials, sputtered alumina
films fabricated at operating pressures of 7 mTorr and higher were found to react with DI water within minutes,
even under mild conditions. X-ray diffraction (XRD) and spectroscopic ellipsometry (SE) showed that the assputtered films had amorphous structures with various degrees of porosity within the films. The calculated
porosity was found to increase from 17% to 25% as the operating pressure increased from 3 to 20 mTorr,
respectively. Field-emission scanning electron microscopy (SEM) was employed to characterize the morphologies
of the corroded films. Attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy showed
the presence of hydroxide-containing functional groups on surfaces of alumina films, suggesting that the
corrosion was due to a hydrolysis reaction. X-ray photoelectron spectroscopy (XPS) revealed distinct features in
the non-corroded and corroded sample groups. For the corroded group (7–20 mTorr), the Al 2p peak showed two
transitions, at 74.2 and 75.5 eV, attributed to Al–O and Al–OH, respectively. The O 1s peak intensities associated
with the hydroxide content of samples in this group were found to be stronger than those associated with the
lattice oxygen. The O 1s signal from adsorbed water at 533.7 eV became much stronger in corroded samples. The
results also show that films fabricated at higher operating pressures yielded higher levels of pre-adsorbed hydroxide. Corrosion may progress through collective processes, including the formation of soluble aluminum
hydroxide complex species and Al–O bond breaking during the proton transfer reactions between adsorbed water
and hydroxide. |
Publication
Journal Publication
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