Using an Al reaction layer to control the morphology and optical properties of ZnO nanorods and nanowalls

This paper reports a novel method for the synthesis of ZnO nanorods, nanowalls, and nanorod/wall structures directly on a substrate, using a simple chemical bath deposition process. The morphology of the resulting structures can be altered simply by adjusting the thickness of an Al thin film, which is used as a doping source. Transmission electron microscopy (TEM) and selected area electron diffraction (SAED) measurements revealed that the resulting ZnO formations possess a wurtzite structure. Inductively coupled plasma mass spectrometry (ICP-MS) revealed that the Al doping of the nanostructures is between 2.1 at% and 4.9 at%. The predominance of violet-blue emissions in the CL spectra of Al-doped and undoped ZnO indicates the presence of interstitial zinc (Zn_i) and zinc vacancies (V_Zn). In this study, the work function was adjusted between 3.81 and 4.39 eV simply by varying the thickness of the Al reaction source.