Alexandria Digital Research Library

Characterizing local structure in complex oxides with quantitative scanning transmission electron microscopy

Author:
Zhang, Jack Y.
Degree Grantor:
University of California, Santa Barbara. Materials
Degree Supervisor:
Susanne Stemmer
Place of Publication:
[Santa Barbara, Calif.]
Publisher:
University of California, Santa Barbara
Creation Date:
2016
Issued Date:
2016
Topics:
Engineering, Condensed matter physics, and Materials science
Keywords:
Complex oxides
Dopant imaging
STEM
Nickelates
Titanates
TEM
Genres:
Dissertations, Academic and Online resources
Dissertation:
Ph.D.--University of California, Santa Barbara, 2016
Description:

Perovskite oxides remain a material class with properties that can be difficult to predict. Strong electron correlations, coupling between electron, lattice, spin and orbital degrees of freedoms, combined with the versatility of the structure itself, result in a wide range of properties, with unique emergent phenomena that occur only at heterointerfaces. Structure plays an especially important role in determining the properties of perovskite oxides. Small distortions in the lattice, particularly rotations or tilts of the oxygen octahedra, can have large effects on the material's electrical and magnetic properties. One way we can tune these rotations is by growing thin film heterostructures, allowing us to tailor the properties of these materials in ways not possible in the bulk. Therefore, determining the local atomic structure in these films is critical for understanding the structure-property relationships, and the origin of any emergent behavior that may exist at an interface.

To that end, we utilize scanning transmission electron microscopy (STEM) to develop a link between the atomic structure and electrical/magnetic properties of three different systems: SrTiO3 quantum wells between GdTiO 3 and SmTiO3, GdTiO3 quantum wells between SrTiO 3, and strained NdNiO3. Using real-space and diffraction techniques, we obtain quantitative information on local octahedral rotations and observe the presence/absence of structural transitions. This information gives us new insight into the driving forces behind the metal-insulator transition and magnetic behavior of the different material systems. We also continue the development of quantitative STEM for precise and accurate determination of 3D dopant atom configurations by using variable detector angles in the high angle annular dark field regime. By demonstrating the usefulness of obtaining angle-resolved scattering data, we provide a new avenue for improving STEM image contrast and atom visibility for future studies.

Physical Description:
1 online resource (180 pages)
Format:
Text
Collection(s):
UCSB electronic theses and dissertations
ARK:
ark:/48907/f39c6xhj
ISBN:
9781369146899
Catalog System Number:
990046969340203776
Rights:
Inc.icon only.dark In Copyright
Copyright Holder:
Jack Zhang
File Description
Access: Public access
Zhang_ucsb_0035D_13038.pdf pdf (Portable Document Format)