A new methodology allowing composition control of thin film complex oxides with a volatile constituent will be developed. This technique will be demonstrated in bismuth ferrite, which is a crystalline solid having material properties of current technological interest. This new processing approach will allow dramatic reduction composition-related defects at the nanoscale, and in doing so, provide for dramatic improvements in the electrical properties. Of premier interest is the ability of bismuth ferrite to couple electrical and magnetic fields: this capability is widely regarded as the cornerstone of a new generation of multifunctional sensing, actuating, and data storage devices. For example, devices offering unprecedented and simultaneous sensing of electrical, acoustic, and magnetic fields will be enabled, and are extremely attractive for applications such as remote surveillance. These opportunities can be fully harnessed only if the improvements offered by this research are realized. Through the duration of this program, a minimum of one graduate student and two undergraduate students will be active participants, and each summer semester, this program will support a Materials Science educational outreach activity. This activity will involve learning workshops for K-12 science teachers, which focus on empowering K-12 educators to incorporate the Principles of Materials Science, specifically at the nanoscale, to their curriculum.
TECHNICAL DETAILS: The proposed program explores fundamental relationships between defect chemistry, crystalline structure, and the electrical properties of ferroelectric thin films. The cornerstone of this investigation involves a novel thin film processing methodology controlling cation stoichiometry and point defects in BiFeO3 through gas-phase equilibrium. This represents a fundamental contribution to thin film processing science since nearly all commercial and military electronic materials rely on property optimization in part through defect equilibrium engineering. A similarly sophisticated capacity has not been developed for electroceramic thin films, thus a major opportunity in thin film property engineering remains untapped. The proposed synthesis technique will enable this optimization in numerous systems holding promise for dramatic property improvement, and insight into defect-related phenomena. In the course of their research, the participating graduate and undergraduate students will develop a cutting-edge gas-phase/condensed-phase equilibrium method for actively tuning defect equilibria. In doing so, they will identify defect equilibria - property relationships in thin films, which represents an important advancement in Materials Science, especially at the nanoscale, where the impact of defects becomes more pronounced.
