IMSS Seminar (17-03)

Start2017/08/25(Fri) 3:00 PM
End2017/08/25(Fri) 4:30 PM
VenueMeeting room on the 2nd floor in the PF building
TitleThermodynamic processes and their implications for low temperature transport at complex oxide interfaces and surfaces
SpeakerDr. Felix Gunkel, RWTH Aachen University・Senior Scientist


Low-dimensional electron transport observed along complex oxide heterointerfaces has attracted enormous attention in recent years. While the formation of these 2-dimensional electron gases is generally attributed to electronic charge transfer triggered by a built-in electric field, the ionic defect structure at these interfaces is still being discussed controversially.

Here, we address the thermodynamic processes associated with built-in electric fields and derive ionic defect concentration profiles established at polar/non-polar oxide interfaces. [1] As we discuss, the specific ionic-electronic defect structure stabilized within such interfacial space charge layers strongly depends on ambient oxygen partial pressure applied during sample fabrication and on the strength of the built-in electric field.

As we ground states obtained for various oxide heterostructure systems [2] and discuss resulting implications for important measures characterizing the electron gas, such as electron mobility [3] as well as its magnetic signature [4], both controllable by thermodynamic means. The thermodynamic model obtained for oxide heterointerfaces is furthermore linked to kinetic space charge formation occurring at complex oxide surfaces [5, 6].

[1] F. Gunkel et al., "Defect concentration profiles at complex oxide interfaces", Physical Review B 93, 245431 (2016)

[2] F. Gunkel et al., "Thermodynamic ground states of complex oxide heterointerfaces", ACS Applied Materials & interfaces, ACS Appl. Mater. Interfaces, 9 (1), 1086 (2017)

[3] C. Xu et al., "Disentanglement of growth dynamic and thermodynamic effects in LaAlO3/SrTiO3 heterostructures", Scientific Reports 6, 22410 (2016)

[4] F. Gunkel, et al., "Defect-control of anomalous and conventional electron transport in NdGaO3/SrTiO3 heterostructures", Physical Review X, 6, 031035 (2016)

[5] R. Meyer et al., "Dynamics of the metal-insulator transition of donor-doped SrTiO3", Physical Review B 94, 115408 (2016)

[6] M. Andrae et al., "Oxygen partial pressure dependence of surface space charge formation in donor-doped SrTiO3", APL Materials 5, 056106 (2017)