Radiation Damage and Radiation-Based Device-Fabrication Techniques in LiNbO3
Creators: Huang, Hsu-Cheng
Publisher: name: Columbia University
Year: 2015
Subjects: Electrical engineering
Materials science
Optics

description: 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.