Epitaxial Growth Mechanism for Perovskite Oxide Thin Films under Pulsed Laser Irradiation in Chemical Solution Deposition Process

We have studied the epitaxial growth of perovskite manganite LaMnO(3) (LMO) on SrTiO(3)(100) and LaAlO(3)(100) substrates by means of chemical solution deposition assisted by pulsed UV laser irradiation, termed excimer laser-assisted metal organic deposition (ELAMOD). Cross-sectional transmission electron microscopy observations revealed that the LMO was crystallized from a coated amorphous LMO matrix by the pulsed laser irradiation, and was preferentially grown from the substrate surface. In this process, the optical absorbance of the substrate for the irradiated laser plays an essential role for starting the epitaxial growth. This indicates a photochemical effect due to the UV laser irradiation; the photochemically activated growth interface strongly enhanced chemical bond formation, leading to epitaxial growth of LMO. The film temperature under the excimer laser irradiation was estimated using theoretical simulations with a one-dimensional heat equation, and it was found to increase to about 1000-1800 degrees C for 90 ns. The photothermal temperature rise contributes to ion-migration for crystallization, and furthers the rapid epitaxial growth initiated by the photochemical effect. Thus, the photochemical and photothermal effects are considered to assume the roles of initiator and enhancer of epitaxial growth under the laser irradiation in the ELAMOD process.