| AVS 65th International Symposium & Exhibition | |
| Novel Trends in Synchrotron and FEL-Based Analysis Focus Topic | Thursday Sessions |
| Session SA+MI-ThM |
| Session: | Ultra-fast Dynamics for Magnetic and Quantum Systems |
| Presenter: | Saeed Yousefi Sarraf, West Virginia University |
| Authors: | S. Yousefi Sarraf, West Virginia University G.B. Cabrera, West Virginia University R. Trappen, West Virginia University N. Mottaghi, West Virginia University S. Kumari, West Virginia University C.-Y. Huang, West Virginia University A. Bristow, West Virginia University M.B. Holcomb, West Virginia University |
| Correspondent: | Click to Email |
Perovskite oxides (ABO3) are a promising class of transition metal oxides that have attracted significant attention in material science due to diverse range of properties. Many studies on structural and magnetic properties have been done on perovskite oxides to base the multifunctional devices made by and proposed for these materials. Yet another very important property of perovskite oxides is that many of their band gaps are in the visible range. These gaps make these oxides a suitable choice for photovoltaic applications. However, despite the very critical role this property plays in light harvesting devices, there has been a limited understanding about the carrier dynamics of these materials, which inform us about the efficiencies of photovoltaic devices, especially in lower thicknesses. Since by decreasing the film thickness, the surface to bulk ratio increases and surface electrons dominate the bulk electrons, surface recombination might occur as an extra channel of energy relaxation, which decreases the device efficiency. Perovskite oxide La0.7Sr0.3MnO3 (LSMO) thin films were fabricated with different thicknesses by pulsed laser deposition on (100) SrTiO3 single crystal substrates. Our films’ quality were checked by in situ RHEED patterns and oscillations, X-ray diffraction and reflectivity, magnetometry and atomic force microscopy. Ultra-fast carrier dynamics were studied by a degenerate reflectivity pump probe setup at 800nm for different film thicknesses and different pump powers. For films with a thickness above ~20nm three different recombination were observed, attributed to electron phonon relaxation, spin lattice phonon assists relaxation and thermal diffusion relaxation. However, for films thinner than ~20nm an extra relaxation mechanism was observed, which we attributed to surface recombination. This optics work was funded by the American Chemical Society (PRF #56642-ND10); sample growth and optimization were supported by NSF (DMR-1608656).