Yuan-Chang Liang

Crystal synthesis and effects of epitaxial perovskite manganite underlayer conditions on characteristics of ZnO nanostructured heterostructures

This study presents the synthesis of high-density aligned wurtzite ZnO nanostructures using thermal evaporation on perovskite (La,Sr)MnO3(LSMO) epitaxy to form a heterostructure without the assistance of metallic catalysis. LSMO epitaxial films are RF-sputtered with various crystal qualities to examine the correlation between the interface and electrical characteristics of the heterostructures. The ZnO nanostructures-LSMO epitaxial heterostructures show electrical rectifying behavior without inserting an ultrathin insulating layer at the hetero-interface. Misfit strain, intrinsic strain, and crystal defects are major factors in causing a phase separation in the as-prepared manganite LSMO epitaxial films. The coexistence of a charge-ordered insulating domain and a ferromagnetic metallic domain causes inhomogeneous electrical contact at the ZnO-LSMO heterointerfaces, further deteriorating the junction characteristics. A high-temperature annealing procedure and moderate LSMO epitaxy film thickness are required for the construction of an efficient ZnO nanostructures-LSMO epitaxy junction.

Microstructure-Dependent Visible-Light Driven Photoactivity of Sputtering-Assisted Synthesis of Sulfide-Based Visible-Light Sensitizer onto ZnO Nanorods

The ZnO-CdS core-shell composite nanorods with CdS shell layer thicknesses of 5 and 20 nm were synthesized by combining the hydrothermal growth of ZnO nanorods with the sputtering thin-film deposition of CdS crystallites. The microstructures and optical properties of the ZnO-CdS nanorods were associated with the CdS shell layer thickness. A thicker CdS shell layer resulted in a rougher surface morphology, more crystal defects, and a broader optical absorbance edge in the ZnO-CdS rods. The ZnO-CdS (20 nm) nanorods thus engaged in more photoactivity in this study. When they were further subjected to a postannealing procedure in ambient Ar/H2, this resulted in the layer-like CdS shell layers being converted into the serrated CdS shell layers. By contrast, the ZnO-CdS nanorods conducted with the postannealing procedure exhibited superior photoactivity and photoelectrochemical performance; the substantial changes in the microstructures and optical properties of the composite nanorods following postannealing in this study might account for the observed results.