Despite being ubiquitous and highly functional, oxide materials containing transition metal elements have barely made it into the application space of electronic and photonic devices. One major roadblock is their material quality which, if compared to bulk single crystals, is generally inferior when synthesized in thin film form. The growth of phase pure material with high structural perfection has been a formidable, but solvable task and atomically abrupt interfaces, well defined heterostructures, and artificially layered oxide compounds have been successfully grown by physical vapor deposition techniques. However, achieving a level of material perfection where unintentional point defect concentrations are low enough to meet the stringent requirements demanded by electronic and photonic application has been found extremely challenging.
In this talk I will present recent progress in the maturation of the thin film quality of transition metal oxides an alternative synthesis approach. Hybrid molecular beam epitaxy (MBE) combines the advantages of conventional MBE and chemical beam epitaxy (CBE) and has allowed to overcome some of the existing synthesis challenges in complex perovskite oxides in general and vanadate compounds in particular, which will be discussed exemplary using SrVO3 – a metal exhibiting sizeable electron correlation effects. The specific example of correlated metals for the application as transparent conductor is given to illustrate how transition metal perovskite oxides offer new material design strategies beyond the realms of conventional semiconductor choices. It will be shown that the high carrier effective mass arising from the mass renormalization due to the strong electron interaction is key to strike a new balance between the mutually exclusive demands of a high electrical conductivity with metal-like carrier concentration and high optical transparency in the visible range. The huge potential of this material class is exemplified by discussing the figure of merit of transparent conductors, which is comparable to the industry standard of the transparent conductor tin-doped indium oxide (ITO) albeit for much thinner films and lower cost of raw material. It will be shown that upon changing the in the perovskite structures opportunities superior to conventional materials choices can be realized.
Seminars are open to alumni, friends of the Department, and the general public.