Oxides pose a noticeable challenge to density functional theory as standard treatments of the exchange-correlation interaction suffer from several severe shortcomings. Furthermore, these materials exhibit large unit cells, and the relaxations and reconstructions of their surfaces is largely unexplored. The latter includes, amongst others, the concentration of surface or near-surface oxygen vacancies. We also note that the surface structure is controlled by the composition, pressure, and temperature of the environment. Also the doping (intentionally or unintentionally) of the bulk results in the formation of a mesoscopic space-charge layer with significant influence on the surface energies and stabilities.
All this is considered in the PhD project where we compute surface structure, stability, and energy of Ga2O3 surfaces as a function of doping levels, O2 pressure, and temperature. This task also requires some method developments. Close contact with experimental groups is essential for the success.
Major accomplishments expected:
Surface structure, stability, and energy of Ga2O3 surfaces as a function of — doping levels, — O2 pressure, — temperature. This is also relevant for the shape of nano (and bigger) crystals. The developed methodology enable later studies for other systems with bigger unit cells, as e.g. In2O3.
Collaboration with partners in the project:
Cluster C3 “Fundamentals of Growth”, i.e. Günther Wagner and Oliver Bierwagen.
Collaboration with clusters is highly favourable, in particular with C4 “Atomic defects”, doping and defect engineering and later on with regards to the fabrication of devices with FBH and UL.
Sebastian Kokott has been working at the Theory Department of the Fritz-Haber-Institut, Berlin, since January 2014. His group, led by Sergey V. Levchenko, conducts research into solid state physics with a special focus on the application of density functional theory (DFT) to oxide materials. Sebastian’s PhD project is about the description of charge carriers and their interactions with lattice vibrations, so-called polarons, in MgO, ZnO, and TiO2.
The Leibniz ScienceCampus GraFOx is a network of two Leibniz Institutes, two universities and one institute of the Max Planck Society. It is based in Berlin, Germany.
Paul-Drude Institut für Festkörperelektronik (PDI)
Leibniz-Institut im Forschungsverbund Berlin e.V.
Tel.: +49 30 20377-342
Prof. Dr. Henning Riechert, PDI
Dr. Oliver Bierwagen, PDI
Dr. Martin Albrecht, IKZ