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Download as PDFSelf-assembled Hetero-structured Oxides
We are studying BiFeO3/CoFe2O4 oxide composite thin films, which have the remarkable characteristic of self-assembling into vertical nanostructures during their deposition on a single crystal substrate, typically SrTiO3. Through the characterization of the structural (Figure 1), magnetic, and electric properties of samples deposited under varying conditions, we are studying the processes happening during deposition that govern the self-assembly of such thin films. A better understanding of the magnetoelectric coupling and strain relationships, due to the coherent interfaces between the three phases, will allow us to fine-tune their magnetic, ferroelectric and multiferroic properties for potential applications.
We demonstrated that these hetero-structured thin films can successfully be grown using a novel alternated-target deposition method, where two ceramic targets of single component BiFeO3 and CoFe2O4 are successively moved under the laser beam for ablation for a given number of pulses (Figure 2). The ratio of pulses on the two targets allows good control of the composition of the film, whereas the total number of cycles controls the thickness of the film. In contrast to the commonly used deposition by ablation from a single target, this alternated method allows fine-tuning of the average composition of the film at different stages of the growth, without the need to fabricate a new target for each desired ratio of the two phases.
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- Figure 1: SEM of the surface of the film. The brighter rectangular structures are CoFe2O4 pillars; the darker background is the BiFeO3 matrix. (inset: XRD pattern close to the substrate peak showing epitaxial relationship between the three components).
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- Figure 2: Schematic of the deposition process, in which two single component targets are alternatively ablated under the laser to give the desired composition.
