Materials synthesis and annealing-induced changes of microstructure and physical properties of one-dimensional perovskite-wurtzite oxide heterostructures

RF sputtering at 750 °C was conducted to synthesize (La,Sr)MnO3 (LSMO)-ZnO one-dimensional (1D) heterostructures on cross-linked ZnO nanostructures. The prepared LSMO-ZnO 1D heterostructures were subsequently annealed at a range of thermal annealing temperatures (800-950 °C) to investigate the structural and physical properties of the 1D heterostructures. X-ray diffraction patterns show how well crystalline LSMO nanolayers formed on the ZnO nanostructures. Auger electron spectroscopy analysis shows that the constituent elements of LSMO were homogeneously distributed on the ZnO surfaces of interest. Scanning electron microscopy and transmittance electron microscopy images show that the morphology of the as-deposited 1D heterostructures consists of round LSMO tiny grains covering the ZnO nanostructures; however, the high-temperature annealed samples are transformed to feature relatively large and oval grains. The high-temperature annealing procedure in oxygen-rich ambient conditions enhanced the saturation magnetization and Curie temperature of the LSMO-ZnO 1D heterostructures. This is associated with an enhancement of the exchange interaction between two neighboring Mn ions through the 2p oxygen orbital in the LSMO nanolayers with reduced crystal defects after high-temperature annealing.