Facile Synthesis and Photoluminescence Mechanism of ZnO Nanowires Decorated with Cu Nanoparticles Grown by Atomic Layer Deposition

Vertically aligned ZnO nanowires (NWs) decorated with Cu nanoparticles (NPs) were successfully prepared on Si (100) by a hydrothermal method together with atomic layer deposition (ALD). By varying the number of ALD cycles, the size and concentration of Cu NPs on the ZnO NWs can be accurately controlled. Scanning electron microscopy and transmission electron microscopy were applied to demonstrate the formation of Cu NPs on ZnO NWs. Study of the photoluminescence (PL) characteristics of ZnO NWs decorated with different densities of Cu NPs show a gradual change in the near-band edge emission and deep level emission with an increasing number of ALD cycles. The enhancement of PL with a decreasing number of ALD cycles was because of decreasing the size of the Cu NPs. The results are discussed considering two major physical phenomena taking place at the interface between Cu NPs and ZnO NWs, namely, passivation of surface dangling bonds of ZnO NWs by Cu NPs and formation of a Schottky contact at the boundaries between them. This work not only indicates that ALD is an excellent technique to grow conformal Cu NPs with highly controllable size but also demonstrates that the surface passivation and electron transfer between Cu and ZnO can efficiently manipulate the PL intensities of ZnO NWs.