Atomic layer deposition of ZnO on ultralow-density nanoporous silica aerogel monoliths

We report on atomic layer deposition of an similar to 2-nm-thick ZnO layer on the inner surface of ultralow-density (similar to 0.5% of the full density) nanoporous silica aerogel monoliths with an extremely large effective aspect ratio of similar to 10(5) (defined as the ratio of the monolith thickness to the average pore size). The resultant monoliths are formed by amorphous-SiO2 core/wurtzite-ZnO shell nanoparticles which are randomly oriented and interconnected into an open-cell network with an apparent density of similar to 3% and a surface area of similar to 100 m(2) g(-1). Secondary ion mass spectrometry and high-resolution transmission electron microscopy imaging reveal excellent uniformity and crystallinity of ZnO coating. Oxygen K-edge and Zn L-3-edge soft x-ray absorption near-edge structure spectroscopy shows broadened O p- as well as Zn s- and d-projected densities of states in the conduction band. (c) 2005 American Institute of Physics.