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The Interplay of Surface Adsorbates and Cationic Intermixing in the 2D Electron Gas Properties of LAO-STO Heterointerfaces

Akrobetu, Richard K
http://rave.ohiolink.edu/etdc/view?acc_num=case1491575404930072

Abstract Details

2017, Master of Sciences (Engineering), Case Western Reserve University, Materials Science and Engineering.
Ever since its discovery merely over a decade ago, the phenomenon of a tunable 2D electron gas at the heterointerface of SrTiO3 (STO) and LaAlO3 (LAO) has been a source of keen interest and scientific debate. Amongst the list of obstacles in understanding this phenomenon are the understanding of the role of surface adsorbates, the difficulty in elucidating the degree of intermixing at the LAO-STO interface, and marking the heterointerface itself. Films of varying thicknesses grown via Pulsed Laser Deposition (PLD) at varying O2 partial pressures and temperatures were studied. The role of surface adsorbate was investigated via detailed in-situ X-ray Photoelectron Spectroscopy (XPS). O1s regions were split into three components with the main peak identifying main oxide oxygen, while the two shoulder peaks, at ~1 and ~2 eV from the main peak, respectively, were related to hydrous and carbonaceous species. Links between differences in their respective ratios, their energies of bond formation, and ambient atmosphere exposure were established. Changes in the peak ratios vs. temperature were then related to binding energies of adsorbed species and the oxygen content from carbonaceous adsorbates through detailed analyses of C1s regions. Investigations into mechanisms of cationic intermixing were cognizant of conventional electron microscopy methods, which are limited by the respective masses of the atoms present and the small length of the interface examined. Films were subjected to surface and depth analyses via Secondary Ion Mass Spectrometry (SIMS). Intermixing was studied as a function of deposition temperature and film thickness by utilizing fragmented ions containing cations of both the film and the substrate through the use of proprietary Matlab software, and were modeled in 3D with Avizo modeling software. The position of the heterointerface was also marked by tracking a minor amount of Cr+ ions present on the surface of the substrate prior to deposition. Finally, evidence of a temperature-driven intermixing mechanism was established by studying the extent of La+ interdiffusion into the substrate at varying temperatures. All these investigations added to ongoing conversations on the effects of extrinsic mechanisms on the LAO-STO system and its efficacy in the fabrication of functional oxide electronics.
Alp Sehirlioglu, PhD (Advisor)
James McGuffin-Cawley, PhD (Committee Member)
Peter Lagerlof, PhD (Committee Member)
111 p.
Chemistry; Engineering; Materials Science; Physics
LAO; STO; pulsed laser deposition; adsorbates; adventitious; intermixing; thin films; XPS; ToF SIMS; SIMS; perovskite; oxide electronics; electron gas; heterointerface, electroceramics

Recommended Citations

Citations

  • Akrobetu, R. K. (2017). The Interplay of Surface Adsorbates and Cationic Intermixing in the 2D Electron Gas Properties of LAO-STO Heterointerfaces [Master's thesis, Case Western Reserve University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=case1491575404930072

    APA Style (7th edition)

  • Akrobetu, Richard. The Interplay of Surface Adsorbates and Cationic Intermixing in the 2D Electron Gas Properties of LAO-STO Heterointerfaces. 2017. Case Western Reserve University, Master's thesis. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=case1491575404930072.

    MLA Style (8th edition)

  • Akrobetu, Richard. "The Interplay of Surface Adsorbates and Cationic Intermixing in the 2D Electron Gas Properties of LAO-STO Heterointerfaces." Master's thesis, Case Western Reserve University, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=case1491575404930072

    Chicago Manual of Style (17th edition)

case1491575404930072
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© 2017, all rights reserved.
This open access ETD is published by Case Western Reserve University School of Graduate Studies and OhioLINK.