Oxygen partial pressure dependence of memory effect of sputtered nc-Al/α-Al2O3 thin films

Nanocrystalline aluminum embedded in amorphous dielectric alumina matrix thin films (nc-Al/α-Al2O3) was synthesized via reactive magnetron sputtering. The nc-Al/α-Al2O3 films at different oxygen partial pressures were sputtered on p-type Si substrates from a pure Al target in the mixed ambient of Ar and O2. Both deposition rate and aluminum concentration increase as the oxygen partial pressure decreases. X-ray photoelectron spectroscopy and high-resolution transmission electron microscope studies give the confirmation of nanocrystalline Al embedded in amorphous Al2O3 matrix. This nanocomposite thin film exhibits memory effect as a result of charge trapping. The flat band voltage value depends on the Al nanocrystal concentration which is related to oxygen partial pressure.