| AVS 54th International Symposium | |
| Thin Film | Wednesday Sessions |
| Session TF-WeM |
| Session: | Thin Film and Nanoparticle Growth and Characterization |
| Presenter: | B. Poelsema, University of Twente, The Netherlands |
| Authors: | B. Poelsema, University of Twente, The Netherlands E. Van Vroonhoven, University of Twente, The Netherlands |
| Correspondent: | Click to Email |
The growth of ultrathin silver films at 750 K on Pt(111) has been studied with LEEM. The STM-based previous reports on surface confined alloying in this bulk immiscible system are confirmed. This information is inferred from the evolution of the electron reflectivity as well as indirectly from the distribution of adatom islands indicative of highly unconventional nucleation behavior extending to extremely high coverages. De-alloying as previously reported is also confirmed basically. The in-situ mesoscopic data, however, reveal a number of previously unnoticed features. For instance de-alloying is accompanied by strong segregation effects. Platinum-rich disks evolve during de-alloying, showing up as persistent "dark spots" in a bright field measurement, irrespective of the energy of the probing electrons. Also no additional diffraction features spots are observed, indicative of the Pt-disks being highly disordered, amorphous or possibly liquid. In a very narrow coverage window around 85% of a monolayer µ-LEED measurements demonstrate a sudden stress relieve. At this point the de-alloying reaches a summit and the film temporarily releases stress by expansion. This goes together with enhanced segregation. Further along the route to monolayer completion we observe reentrant alloying which actually persists during the growth of a few more layers. Also the film quickly resumes its pseudomorphic structure.