Surface Photoluminescence Emission of ZnO Nanorod Arrays: Experimental and First-Principles Investigation

The photoluminescence emission of ZnO nanorods was investigated experimentally and by first-principles calculations. Nanorod arrays of ZnO were used because it is easy to treat the surface and their morphologies simplify first-principles calculations. The nanorod array samples were coated with various oxides (TiO 2, Y 2 O 3, CeO 2, and Er 2 O 3 ) by sputtering. The orange-to-red emission intensity decreased dramatically on applying an oxide coating for all four coating materials, whereas the UV and green emissions were affected little by the coatings. This indicates that surface luminescent centers generate the orange-to-red emission. In this study, the electronic energy state of the surface was calculated by first-principles calculations, using the discrete-variational Xα molecular orbital method. The calculation results reveal that the surface energy levels of ZnO provide favorable conditions for broad orange-to-red emission.