Theses Doctoral

Radiation Damage and Radiation-Based Device-Fabrication Techniques in LiNbO3

Huang, Hsu-Cheng

The study of radiation effects in materials and devices has been of much interest
for a broad variety of scientific reasons and applied purposes. Examples are the
investigation of the robustness of devices under radiation environments, interstellar space,
or the use of irradiation for device-fabrication methods such as ion implantation. Thus, a
fundamental understanding of the irradiation-induced change in materials properties is
crucial of applied science. In this thesis, investigation of radiation damage in complex
oxides, especially LiNbO3 and its related device, was carried out. Different radiation
sources were examined, including light and heavy ion, electron and gamma rays. A set of
instruments were employed to probe induced damage from different perspective. These
instruments include optical methods (optical microscopy and micro-Raman spectroscopy),
ion beam analysis (Rutherford backscattering spectroscopy), and direct visualization
(SEM, TEM and AFM). It was found that the degree of ion-matter interaction (stopping
power) plays a major role in initiating damage. Different forms of damage, including
surface deformation, material amorphization, defect clusters, and long-range strain field,
were observed. Probing the response of oxide crystals with these tools provides a
comprehensive basis for better comprehension of radiation damage. The detailed studies
and their findings are described in more details in Chapters 4, 5, and 7.
In addition to the materials characterization, the impact of radiation effects on one
specific active device (thin-film electro-optic modulator) was also studied. It was found
that radiation dose and distribution both affect device performance. More details are in
Chapter 6.
Our knowledge of these radiation effects allow us to utilize and engineer this
damage for the development of advanced radiation-enabled device fabrication techniques.
Both light- and heavy-ion irradiation were studied and it was found that the nature of their
different damage mechanisms lead to essentially a different response to wet chemical
etching. Using radiation-enabled selective etching allowed use to explore new or improved
techniques for fabricating sub-um-thick LiNbO3 thin film and high-resolution patterning.
Co-irradiation of both ion species was also investigated and this method shows easy
fabrication of patterning on freestanding thin film. The characteristics of these methods
make them useful for the fabrication of the current and future photonic integrated
platforms. More details are in Chapters 3 and 8.
In addition to radiation damage study, other materials-based fabrication methods
were investigated - particularly those that were a consequence of our materials fabrication
studies. For example, domain engineering of ferroelectric materials (poling) for nonlinear-optic applications was investigated and it was found that domain broadening can be
sufficiently suppressed using a thinned sample. More details are in Chapters 3.


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More About This Work

Academic Units
Electrical Engineering
Thesis Advisors
Osgood, Jr., Richard M.
Ph.D., Columbia University
Published Here
February 24, 2015