Issue 45, 2019

Coherent acoustic phonons and ultrafast carrier dynamics in hetero-epitaxial BaTiO3–BiFeO3 films and nanorods

Abstract

The desire for multifunctional devices has driven significant research toward exploring multiferroics, where the coupling between electric, magnetic, optical, and structural order parameters can provide new functionality. While BiFeO3 is a well studied multiferroic, recent research has shown that the addition of BaTiO3 can improve the material properties. In this study, we perform time resolved differential reflectivity measurements of (1 − x)BaTiO3–(x)BiFeO3, with x = 0.725 epitaxial films grown on a lanthanum strontium manganite (LSMO) layer with a strontium titanate (STO) substrate, and BaTiO3–BiFeO3 nano-rods grown on Pt/Si. Our time resolved measurements can be used to probe dynamical properties on picosecond time scales. Information obtained is vital towards the design and understanding of high speed devices that incorporate multiferroic materials. We find that the contribution to the transient reflectivity response of a BaTiO3–BiFeO3 film due to carrier dynamics can be quantitatively explained by the diffusion of the photoexcited carriers away from the surface and that the ambipolar diffusion constant is below 1–2 cm2 s−1. At low temperature and for thicker films, in addition to a response from carrier dynamics, we also observed oscillations in the transient reflectivity with periods of 30–37 ps. We attribute these oscillations to propagating coherent acoustic phonons in the films. In the BaTiO3–BiFeO3 nano-rods samples only, we observed an additional oscillation with frequency in the range of 8 GHz. This is close to a theoretically predicted magnon frequency, but the strength of this oscillation only had a very weak magnetic field dependence. Another explanation for this feature could be multiple reflections of the acoustic phonons at the Pt interfaces (due to the large acoustic impedance mismatch).

Graphical abstract: Coherent acoustic phonons and ultrafast carrier dynamics in hetero-epitaxial BaTiO3–BiFeO3 films and nanorods

Article information

Article type
Paper
Submitted
24 mar 2019
Accepted
17 okt 2019
First published
05 nov 2019

J. Mater. Chem. C, 2019,7, 14212-14222

Author version available

Coherent acoustic phonons and ultrafast carrier dynamics in hetero-epitaxial BaTiO3–BiFeO3 films and nanorods

R. R. H. H. Mudiyanselage, B. A. Magill, J. Burton, M. Miller, J. Spencer, K. McMillan, G. A. Khodaparast, H. B. Kang, M. G. Kang, D. Maurya, S. Priya, J. Holleman, S. McGill and C. J. Stanton, J. Mater. Chem. C, 2019, 7, 14212 DOI: 10.1039/C9TC01584A

To request permission to reproduce material from this article, please go to the Copyright Clearance Center request page.

If you are an author contributing to an RSC publication, you do not need to request permission provided correct acknowledgement is given.

If you are the author of this article, you do not need to request permission to reproduce figures and diagrams provided correct acknowledgement is given. If you want to reproduce the whole article in a third-party publication (excluding your thesis/dissertation for which permission is not required) please go to the Copyright Clearance Center request page.

Read more about how to correctly acknowledge RSC content.

Social activity

Spotlight

Advertisements