, Yale University
[Host: Joe Poon]
Quantum-mechanical calculations based on methods that do not require any empirical input (first-principles calculations) have become an indispensable tool in studies of materials properties. In this talk, I will focus on applications of first-principles methods to studies of perovskite oxide surfaces and interfaces. Depending on the choice of cations, oxides can have almost any desired property. I will present two examples of materials that exhibit relation between structure and electronic properties at surfaces and interfaces. First, I will discuss an interface between metallic LaNiO3 thin film and ferroelectric PbTiO3. The polar field created by a ferroelectric can be used to modulate the conductivity of a channel material. This allows one to design non-volatile electronic devices based on the ferroelectric field effect. Typically, in the ferroelectric field effect, switching the polar state of a ferroelectric changes the carrier density in the channel material. I will show that in the LaNiO3/PbTiO3 interface the conductivity of the interface changes due to changes in carrier mobility, which in turn is related to structural distortions at the interface and appearance of two-dimensional conductivity in PbTiO3 at the interface. Second, I will present a study of properties of the (001) surfaces of thin LaNiO3 films. These films show dramatic differences in conductivity depending on the surface termination (LaO vs NiO2). We find that in this case, the conductivity is related to the polar structural distortions appearing at the surfaces of films.
Friday, February 13, 2015
Physics Building, Room 204
Note special room.
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