Chemistry and formation process of Ga(Al)As oxide during local anodic oxidation nanolithography

We present our investigation on the early stage of the photon induced desorption of oxide nanostructures grown on GaAs/AlAs/GaAs heterostructures. The oxide structures were fabricated by local anodic oxidation performed by means of an atomic force microscope. We observed that after a first rapid evolution in which a thick layer of heterogeneous material is removed, the oxide composition remains almost constant. These results support our model in which the oxidation process on a layered material resembles a melting process and produces a mixed material whose composition is the average of the initial one.