Ultra-fast carrier dynamics of La_0.7Sr_0.3MnO₃ thin films

Perovskite oxides (ABO₃) are a promising class of transition metal oxides with a diverse range of properties such as multiferroicity and superconductivity. Many studies have been done on their structural and magnetic properties. Though, La_0.7Sr_0.3MnO₃ (LSMO) is a semi-metal perovskite oxide, when grown with nanometer scale thicknesses, a band gap will form which can be close to the visible range. While this gap makes LSMO a potential choice for photovoltaic applications, there has been a limited understanding about the carrier dynamics of this oxide. LSMO thin films were fabricated by pulsed laser deposition on (100) SrTiO₃ single crystal substrates. A degenerate pump probe setup with a femtosecond laser at 800nm was used to study the ultra-fast free carrier dynamics of LSMO thin films. Subpicosecond, subnanosecond and nanosecond dynamics are observed, which represent Auger, radiative and SRH recombination respectively. Moreover, in ultra-fast and fast regimes, oscillations were observed which can be due to phonons in the thin film or the substrate.