Investigating the Relative Stabilities and Electronic Properties of Small Zinc Oxide Clusters

We report a combined experimental and theoretical study investigating small zinc oxide clusters. A laser vaporization source and a time-of-flight (TOF) mass spectrometer are employed to produce and identify anionic clusters in the ZnnOm (n = 1-6, m = 1-7) size regime. The adiabatic detachment energy (ADE) and vertical detachment energy (VDE) of Zn3O3- and Zn3O4- clusters are determined via anion photoelectron spectroscopy. We have utilized density functional theory (DFT) calculations to explore the possible geometries of neutral and anionic Zn3Om (m = 3-5) clusters, while the theoretical ADE and VDE values are compared with experimental results. The experimentally observed relative abundances among the Zn3Om- (m = 3-5) clusters are investigated through calculations of the detachment energies, dissociation energies, and HOMO-LUMO gaps. We find that the Zn3O3 cluster maintains enhanced stability compared to their oxygen-rich counterparts. Furthermore, by coupling the experimentally obtained photoelectron angular distributions of Zn3O3- and Zn3O4- with electronic structure calculations, the nature of the highest occupied molecular orbitals is discussed, with the goal of aiding the isolation (ligand-capped)/deposition of these building blocks.