<p>Vertically aligned nanocomposite (VAN) configuration has
been recognized as the state-of-the-art architecture in the complex oxide
epitaxial thin films, which are constructed by two immiscible phases
simultaneously and vertically growing on a given substrate and forming various
columnar microstructures, such as nanopillars embedded in matrix, nanomaze, and
nanocheckboard. Due to its architectural features, VAN structure enables a
powerful control on the multifunctionalities via vertical strain engineering,
microstructural variations, and interfacial coupling. It provides flexibility
in complex oxide designs with various functionalities (e.g., electrical,
magnetic, optical, etc.), as well as a platform to explore the correlations
between strain, microstructure, and multifunctionalities of the nanocomposite thin
films.</p>
<p>In this dissertation, integrated VAN systems with multilayer
configuration have been constructed as a new three-dimensional (3D) framework,
e.g., inserting 1-3 layers of CeO<sub>2</sub> (or LSMO) interlayers into the La<sub>0.7</sub>Sr<sub>0.3</sub>MnO<sub>3</sub>
(LSMO)-CeO<sub>2</sub> VAN system and forming 3D interconnected CeO<sub>2</sub>
(or LSMO) skeleton embedded in LSMO matrix. This new VAN 3D framework enables both
lateral and vertical strain engineering simultaneously within the films and
obtains highly enhanced magnetotransport properties, such as the record high
magnetoresistance (MR) value of ~51-66%, compared with its VAN single layer
counterpart. In order to demonstrate the flexibility of this design, other
systems such as 3D ZnO framework embedded in LSMO matrix have been constructed
to explore the thickness effects of the ZnO interlayers on the magnetotransport
properties of the LSMO-ZnO system. The maximum MR value is obtained at the ZnO
interlayer thickness of ~2 nm, which enables the optimal magnetoresistance
tunneling effect. Meanwhile, the significance of the interlayer selection in
the microstructure and magnetoresistance properties of the LSMO-ZnO system has
been investigated by varying the interlayer materials yttria-stabilized
zirconia (YSZ), CeO<sub>2</sub>, SrTiO<sub>3</sub>, BaTiO<sub>3</sub>, and MgO.
The formed 3D heterogeneous framework provides a new dimension to tailor the
microstructure, strain and functionalities within the films.</p>
<p>Moreover, a new strain engineering approach with engineered
tilted interfaces has been demonstrated by multilayering different VAN layers
with various two phase ratio and creating a hybrid nanodumbbell structure
within the LSMO-CeO<sub>2</sub> VAN thin films. The nanodumbbell structure
accomplishes a more efficient strain engineering and exhibits highly enhanced
magnetic and magnetoresistance properties, compared with its VAN single layer
and interlayer counterparts. </p>
<p>These examples presented in the thesis demonstrate the
flexibility and potential of 3D strain engineering in complex VAN systems and a
higher level of property control, coupled with unique microstructures and
interfaces. Beyond perovskites, these 3D designs can be extended to other
material systems for a broader range of applications, such as energy conversion
and storage related applications.</p>
| Identifer | oai:union.ndltd.org:purdue.edu/oai:figshare.com:article/9117023 |
| Date | 02 August 2019 |
| Creators | Xing Sun (7042985) |
| Source Sets | Purdue University |
| Detected Language | English |
| Type | Text, Thesis |
| Rights | CC BY 4.0 |
| Relation | https://figshare.com/articles/CONTROLLABLE_THREE-DIMENSIONAL_STRAIN_MICROSTRUCTURE_AND_FUNCTIONALITIES_IN_SELF-ASSEMBLED_NANOCOMPOSITE_THIN_FILMS/9117023 |
Page generated in 0.0027 seconds