Formation, deposition and examination of size selected metal clusters on semiconductor surfaces: An experimental setup

An instrument designed to investigate the chemical behavior of size selected metal clusters on semiconductor surfaces is described. The clusters are formed using laser vaporization, mass selected in a magnetic mass analyzer and deposited on TiO2 substrates under UHV conditions with impact energies ranging from ≤1 to >100 eV/atom. Intensities of mass selected Aun+ and Agn+ clusters range from 0.03 to 3 nA. Intensity, beam focusing and deposition energy are discussed. Once deposited on the surface, the clusters are investigated using scanning tunneling microscopy (STM) and/or temperature programmed desorption (TPD). Examples are presented showing STM images of Au5 deposited on a clean rutile titania surface and of the TPD of propene from TiO2.