Els investigations of the beginning oxidation on aluminum thin films

ELS and simultaneous quartz microbalance investigations have been carried out on clean aluminum and its surface oxide layer. The loss spectrum of clean Al is interpreted by the collective features of the conduction electrons: volume and surface plasmons, the latter being extremely sensitive to a small oxygen uptake. In the very beginning the oxidation is characterized by a loss peak at 7.3 eV which is attributed to a single electron transition from the O(2p) level to an unfilled state near the Fermi level of the metal. The decreasing intensity of the 7.3 eV loss and the increasing of a second loss at 19.2 eV with further oxygen uptake are tentatively explained by the formation of Al₂O₃ and interband transitions of amorphous Al oxide. The formation of A1₂O₃ is supported by the gravimetric measurements of oxygen mass gain.