Alejandro Díaz Ortiz –
Directing the Self-Growth of 2D Alloys

The paradigm of materials science and engineering is that structure and microstructure determine properties and function. This concept is crucial to materials development since function is forward-linked to performance while structure is back-linked to processing. Structure, however, depends on materials' dimensionality and size, and so the physicochemical properties. The use of bulk thermochemical data to understand and design low-dimensional systems is, therefore, not always warranted.

Two-dimensional alloys on substrates behave in dramatically different ways than their bulk counterparts. Our aim is to tailor not just the ordering trends, as it has been shown for a number of systems before, but to actually create patterns (stripes, compositional dots, etc.) using the symmetry of and the elastic strain induced by the substrate.

Our theoretical and experimental investigations on two-dimensional Fe-Au alloys on Mo(110) reveal an unexpected structural complexity with a series of ordered ground states in the entire composition range. First-principles density-functional analysis shows that changes in the electronic structure due to dimensionality and (to a lesser extent) epitaxial strain are the driving forces behind the ordering reactions. This has to be contrasted to the bulk behavior of Fe-Au alloys that show strong phase separation up to the melting point without forming any intermetallic compound.

The structural analyses are performed using x-ray synchrotron sources at the MPI-MF beamline at the synchrotron radiation source ANKA at the Karlsruhe Institute of Technology.

External collaborators:
Andreas Stierle, University of Siegen, Siegen, Germany
Alina Vlad, Synchrotron Soleil, Paris, France
Madhura Marathe, Bangalore, India
Shobhana Narasimhan, Bangalore, India


There are a series of PhD, Masters, and Diploma job opportunities associated to this project in collaboration with Siegen University. For further information please contact: Alejandro Díaz Ortiz