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Huang, Mengchen (2016) LOCAL PROBE INVESTIGATION OF EMERGENT PHENOMENA IN COMPLEX OXIDE HETEROINTERFACES. Doctoral Dissertation, University of Pittsburgh. (Unpublished)

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Complex oxide heterointerfaces exhibit rich physics as well as many veiled puzzles. LaAlO3/SrTiO3 (LAO/STO) is one of the prototype of such heterointerfaces. In 2004, Ohtomo and Hwang first reported a conducing interface emerged between perovskite oxide insulators LaAlO3 and SrTiO3. Following this seminal discovery, many emergent phenomena like metal-insulator transition, piezoresponse, superconductivity, magnetism, strong spin-orbit coupling and coexistence of superconductivity and magnetism were reported in the fascinating LAO/STO system. However, the origin of the conducting interface is still the subject of intense debate, and the physics behind these emergent phenomena remains a wild space to be explored. My Ph.D. study focused on the emergent phenomena in LAO/STO by using “local probes” — nanostructures created by conductive atomic force microscope (c-AFM) lithography and the AFM itself. I used piezoresponse force microscope (PFM) to study the electromechanical response in LAO/STO and developed a high-resolution, non-destructive PFM imaging technique to visualize nanostructures at LAO/STO interface. The results indicate that the PFM signal is related to a carrier density mediated interfacial lattice distortion, and surface adsorbates can affect the PFM signal via coupling to the electrons at the interface. I integrated graphene on LAO/STO, created field-effect devices in graphene/LAO/STO and collaborated with Dr. Giriraj Jnawali to investigate the transport properties. The high quality single layer graphene on LAO/STO exhibited the half-integer quantum Hall effect and room temperature weak antilocalization behavior. I performed transport measurements in (110)-oriented LAO/STO to investigate anisotropic quasi one-dimensional superconductivity in nanowires. Based on the results I proposed a plausible explanation related to the Lifshitz transition and anisotropic band structures of nanowires in (110)-oriented LAO/STO. Co-worked with Dr. Keith Brown, I studied the conductivity switching of LAO/STO interface by solvent immersion and light exposure. We reported a fully reversible, more than four order of magnitude conductance modulation and proposed a surface protonation model. Besides these main research projects that are discussed in this thesis, I also contributed in many other research projects by optimizing the proper sample preparation methods, performing nanostructures fabrication and characterization, and being actively involved in the measurements, data analysis and manuscript preparation.


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Item Type: University of Pittsburgh ETD
Status: Unpublished
CreatorsEmailPitt UsernameORCID
Huang, Mengchenmeh97@pitt.eduMEH970000-0002-0568-6238
ETD Committee:
TitleMemberEmail AddressPitt UsernameORCID
Committee ChairLevy, Jeremy
Committee MemberLeibovich, Adam
Committee MemberDutt, Gurudev
Committee MemberD'Urso, Brian
Committee MemberPekker, David
Committee MemberLittle, Steven
Date: 30 September 2016
Date Type: Publication
Defense Date: 26 April 2016
Approval Date: 30 September 2016
Submission Date: 29 February 2016
Access Restriction: No restriction; Release the ETD for access worldwide immediately.
Number of Pages: 183
Institution: University of Pittsburgh
Schools and Programs: Dietrich School of Arts and Sciences > Physics
Degree: PhD - Doctor of Philosophy
Thesis Type: Doctoral Dissertation
Refereed: Yes
Uncontrolled Keywords: local probes, complex oxides, emergent phenomena
Date Deposited: 30 Sep 2016 14:29
Last Modified: 15 Nov 2016 14:31


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