Oxygen induced modifications in the growth of ultrathin iron films on Cu3Au(0 0 1)

Codeposition of oxygen and Fe on Cu3Au(0 0 1) has been investigated in order to look at the modifications of the growth regime induced by the chemical additive. Oxygen deeply modifies the growth modes both at relatively low temperature (150 K) and at room temperature (RT). The bilayer growth mode active at earlier stages of growth in absence of the surfactant element is suppressed. We concentrated our investigation on RT deposition. A relatively ordered, pseudomorphic iron film has been found only at low thickness (up to 4 ML). This film is covered with an oxygen layer, whose coverage and order depends on the post-growth annealing treatment. The annealed oxygen layer has been used as a surfactant for further Fe deposition cycles. During deposition, part of the oxygen remains trapped into the film. Restoration of the chemisorbed layer is obtained after annealing at moderate temperature (700 K). As the film thickness increases as a result of successive depositions, the film is first characterized by coexistence of pseudomorphic and bcc patches. The pseudomorphic patches seem stabilized not only by presence of the oxygen, but also by Cu and Au impurities in the film. For relatively large thickness (above 25 ML) bcc domains become majority.