Charge-induced formation of linear Au clusters on thin MgO films:Scanning tunneling microscopy and density-functional theory study

Gold deposition onto ultrathin MgO films on Ag(001) results in the formation of linear Au clusters, as revealed from a combined scanning tunneling microscopy and density-functional theory study. The equilibrium structure of small Au clusters containing three to seven atoms is therefore different on thin film and bulk MgO(001) but also deviates from the shape of the respective gas-phase clusters. The peculiar one-dimensional growth regime of gold is stimulated by an electron transfer from the MgO/Ag interface to the deposited Au clusters, resulting in singly and doubly charged cluster anions. Only for larger atom numbers, the formation of compact two-dimensional clusters prevails on the MgO thin films.