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Growth, Integration, and Transfer of Strained Multiferroic Bismuth-Based Oxide Thin Films

thesis
posted on 2024-06-05, 12:16 authored by James P BarnardJames P Barnard

Thin film materials are used in many areas of our daily lives. From memory storage chips to optical coatings, these thin films are essential to the technologies on which we rely. Multiferroic thin films, a group of materials that simultaneously exhibit ferromagnetism and ferroelectricity, are of particular interest because of the new opportunities that they enable in memory storage and sensors. Bismuth-based oxide materials have proven to be excellent candidates for these applications, with multiferroic properties and anisotropic structures. This novel self-assembled structure found in layered supercell systems has applications in optical devices, such as isolators and beamsplitters. Throughout this study, thin film strain and epitaxy must be tended to as the fundamentals of film growth, adding to the complexity of these challenges.

In this dissertation, bismuth-based oxides, and more specifically the Bi3Fe2Mn2Ox (BFMO) layered supercell phase, are studied from three perspectives. First, BFMO is integrated onto silicon substrates for commercialization using a complex buffer layer stack to mediate the differences in the crystal lattice. This allows for a demonstration of device fabrication with this film. Second, the growth and impact of strain are examined through geometric phase analysis, discovering that strain is essential for the growth of the supercell phase in BFMO. This strain can be tuned through buffer layer addition to optimize the growth of this phase. Third, two methods are demonstrated to free the BFMO material from the typical film-substrate lattice matching requirements. The process of transferring the film from the original substrate onto a different substrate removes these restrictions, allowing virtually unlimited access to applications that were previously not possible. The two methods demonstrate different solutions to the specific challenges of transferring the highly strained BFMO thin film. These findings pave a practical way to integrate multiferroic layered oxide thin films onto chips for the next generation of devices.

Funding

Sandia National Laboratories LDRD Graduate Fellowship

U.S. Office of Naval Research N00014-20-1-2600

History

Degree Type

  • Doctor of Philosophy

Department

  • Materials Engineering

Campus location

  • West Lafayette

Advisor/Supervisor/Committee Chair

Haiyan Wang

Additional Committee Member 2

Xinghang Zhang

Additional Committee Member 3

Mukerrem Cakmak

Additional Committee Member 4

Peide Ye