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EllineHettiaratchyDissertation_final.pdf (9.79 MB)
ETD Abstract Container
Abstract Header
The Structural and Magnetic Characterization of Molecular Beam Epitaxy Grown µ-Fe
2
O
3
/β-Ga
2
O
3
Heterostructures
Author Info
Hettiaratchy, Dona Elline Clarissa
Permalink:
http://rave.ohiolink.edu/etdc/view?acc_num=osu166074990160957
Abstract Details
Year and Degree
2022, Doctor of Philosophy, Ohio State University, Materials Science and Engineering.
Abstract
A new monoclinic phase of Iron (III) Oxide (µ-Fe
2
O
3
) was recently stabilized using plasma-assisted molecular beam epitaxy (PAMBE) on ultrawide-band gap β-Ga
2
O
3
substrates. µ-Fe
2
O
3
is the first new crystal structure for stoichiometric iron oxides discovered in nearly a century. While the epitaxial stabilization of this novel magnetic material has been demonstrated, the structural and magnetic properties of µ-Fe
2
O
3
heterostructures largely remain unexplored. This dissertation is focused on the growth and characterization of heterostructures of µ-Fe
2
O
3
grown on (010) oriented β-Ga
2
O
3
substrates in order to understand the structural and magnetic properties of µ-Fe
2
O
3
. The first part of this work discusses the origin of the ferromagnetic response observed at room temperature from theµ-Fe
2
O
3
/β-Ga
2
O
3
superlattices. To investigate the suspected interface origin of the ferromagnetic phase, identical superlattices of antiferromagnetic µ-Fe
2
O
3
, and diamagnetic β-Ga
2
O
3
are grown on (010) oriented β-Ga
2
O
3
substrates at various substrate temperatures and beam fluxes. The saturation magnetization of the ferromagnetic phase is observed to increase strongly with the interface roughness, consistent with an interfacial origin for the ferromagnetic response. To understand the structural properties of the µ-Fe
2
O
3
/β-Ga
2
O
3
superlattices (layer thicknesses and strain-relaxation), a framework is necessary to quantitatively analyze High Resolution X-ray diffraction (HRXRD) data using simulations based on dynamical X-ray diffraction theory. The next part of this work uses commercially available XRD fitting software, adapted to work with monoclinic crystal structures, to quantitatively characterize superlattices composed of either µ-Fe
2
O
3
or β-(Al
x
Ga
1-x
)
2
O
3
grown on (010) β-Ga
2
O
3
substrates. Reciprocal space maps show coherent superlattice growths that are strained to the (010) β-Ga
2
O
3
lattice. Scanning transmission electron microscopy (STEM) data of a µ-Fe
2
O
3
superlattice shows significant diffusion of Fe atoms into the β-Ga
2
O
3
layers. Finally, this work discusses the growth of bulk µ-Fe
2
O
3
, and the characterization of the Curie temperature, magnetic anisotropy, and band structures of µ-Fe
2
O
3
heterostructures. Bulk µ-Fe
2
O
3
undergoes strain relief through misfit twinning, with a critical thickness of ~8nm (~50 ML). The directional dependence of the magnetic response is characterized using SQUID magnetometry. µ-Fe
2
O
3
heterostructures display perpendicular magnetic anisotropy with an out-of-plane (010) spin-locking axis. Band structures are calculated using DFT for bulk µ-Fe
2
O
3
and the ferromagnetic, ordered interface phases. Bulk antiferromagnetic µ-Fe
2
O
3
has an indirect band gap of E
g
=2.195 eV in the visible and the ordered ferromagnetic interface phase β-(Fe
oct
Ga
tet
)
2
O
3
has a direct band gap of E
g
=2.704 eV. Photoluminescence spectra support the DFT predictions of these band structures. The demonstration of an interface magnetic phase in nearly lattice-matched monoclinic µ-Fe
2
O
3
/β-Ga
2
O
3
with an out-of-plane spin-locking axis, opens the door to ultra-wide band gap heterostructure-engineered magneto-electronic devices, where ferromagnetic switching of the interface phase can be incorporated into high-field devices.
Committee
Dr. Roberto Myers (Advisor)
Dr. Sanjay Krishna (Committee Member)
Dr. Maryam Ghazisaeidi (Committee Member)
Pages
246 p.
Subject Headings
Electrical Engineering
;
Engineering
;
Materials Science
;
Nanoscience
;
Nanotechnology
;
Solid State Physics
;
Technology
Keywords
Materials
Recommended Citations
Refworks
EndNote
RIS
Mendeley
Citations
Hettiaratchy, D. E. C. (2022).
The Structural and Magnetic Characterization of Molecular Beam Epitaxy Grown µ-Fe
2
O
3
/β-Ga
2
O
3
Heterostructures
[Doctoral dissertation, Ohio State University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=osu166074990160957
APA Style (7th edition)
Hettiaratchy, Dona Elline Clarissa.
The Structural and Magnetic Characterization of Molecular Beam Epitaxy Grown µ-Fe
2
O
3
/β-Ga
2
O
3
Heterostructures.
2022. Ohio State University, Doctoral dissertation.
OhioLINK Electronic Theses and Dissertations Center
, http://rave.ohiolink.edu/etdc/view?acc_num=osu166074990160957.
MLA Style (8th edition)
Hettiaratchy, Dona Elline Clarissa. "The Structural and Magnetic Characterization of Molecular Beam Epitaxy Grown µ-Fe
2
O
3
/β-Ga
2
O
3
Heterostructures." Doctoral dissertation, Ohio State University, 2022. http://rave.ohiolink.edu/etdc/view?acc_num=osu166074990160957
Chicago Manual of Style (17th edition)
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Document number:
osu166074990160957
Download Count:
107
Copyright Info
© 2022, all rights reserved.
This open access ETD is published by The Ohio State University and OhioLINK.