Metal-semiconductor-junction-assisted photoluminescence and Optical magnonics in nanostructures

Among the metal oxides, zinc oxides (ZnO) are most likely to be the most functional materials finding many applications1. We recently found that metallic Zn nanoplates also possess unique PL characteristics2, but obviously, the PL emission mechanism is different from that of semiconducting ZnO nanostructures. Here, we demonstrate the varying PL emission mechanisms for semiconducting hollow ZnO nanoballoons, metallic solid Zn nanospheres, and metal-semiconductor concentric solid Zn/ZnO nanospheres. The PL emissions of the semiconducting hollow ZnO nanoballoons are attributed to the near band edge (NBE) and deep level electron transitions, while those of the metallic solid Zn nanospheres are mainly dependent on the electron transitions between the Fermi level (EF) and the 3d band2. The PL emissions of the metal-semiconductor concentric solid Zn/ZnO nanospheres are ascribed to the electron transitions across the metal-semiconductor junction, from the interface states to the valence band, and from the EF to the valence and 3d bands. The three nanostructures have effective visible-light emissions at room temperature, so they are good candidates for use in laser diodes (LDs) and light-emitting diodes (LEDs). In addition, the optical magnonics in nanostructures will be briefly discussed.