In the early beginning of our millennium, the material science community was ignited by reports about a two-dimensional electron gas (2DEG) found at the interface between LaAlO3 and SrTiO3. After such a 2DEG was found also in other oxide hetero-structures, it followed the discovery of a 2DEG on the surface of bare SrTiO3. From the latter, lively discussions emerged about the similarities and differences between the 2DEG on the bare surface and the oxide interfaces - here condensed to the question, whether there is "one 2DEG" and "the other 2DEG"?
I will discuss a very systematic study about the 2DEG on various surface orientations of bare SrTiO3 and the prototypical LaAlO3/SrTiO3 hetero-interface. It will be demonstrated that oxygen vacancies, and therefore the 2DEG, can be prepared by exposure to extreme ultraviolet (XUV) light. Precise control of d1-electron-filling can be archived by a combination of in-situ oxygen dosing and XUV irradiation. The preparation is carefully characterized by photoemission spectroscopy. The sheet carrier density can be cycled back and forth and stabilized at will. In doing this, we are able to widen the view on the important generalities and differences between the "one 2DEG" and "the other 2DEG".
A coffee break will be served at 11h00. The seminar will be given in English.
Séminaire proposé par Nick Barrett