Synergistically enhanced ultraviolet emission of Yb doped ZnO films by using a capping of ultrathin Al and SiO2 microspheres.

ABSTRACT

We studied the enhancement effects of ultraviolet (UV) emission from rare earth ytterbium (Yb) doped ZnO films, by using capping layers of Al and SiO2 micro-spheres. The films were deposited on Si substrates with magnetron sputtering followed by high temperature (∼1000°C) heat treatment, and then capped with a nanoscale ultrathin aluminum (Al) layer and/or SiO2 micro-spheres on the surface of the films. The photoluminescence (PL) results indicate that compared to the case without any capping, the UV emission is enhanced by a factor ranging from several to dozens times, the films capped with 2.0 nm Al layer and 5.0 µm SiO2 microspheres have the longest highest PL intensity among the samples. The PL enhancements are discussed in terms of increased optical (or electrical) fields around the surface of the films combined with defect passivation after the capping. Our work has proposed a strategy to enhance the UV emissions of ZnO, which will broaden the application potential of ZnO in UV photonics.